jugar_probar/

validators.rs

//! Streaming UX Validators (PROBAR-SPEC-011)
//!
//! Validate streaming interface patterns per specification Section 2.
//!
//! ## Toyota Way Application:
//! - **Jidoka**: Real-time quality monitoring during streaming tests
//! - **Poka-Yoke**: State machine validation prevents invalid transitions
//! - **Andon**: Clear alerts when streaming metrics degrade
//!
//! ## References:
//! - [10] Sewell et al. (2010) State machine verification
//! - [11] Blott & Korn (2015) Low-latency patterns
//! - [12] Sohn et al. (2015) VAD state machine testing

use std::collections::VecDeque;
use std::fmt;
use std::time::{Duration, Instant};

// =============================================================================
// VU Meter Configuration (Section 2.4)
// =============================================================================

/// VU meter validation parameters
///
/// # Example
/// ```
/// use jugar_probar::validators::VuMeterConfig;
///
/// let config = VuMeterConfig::default()
///     .with_min_level(0.1)
///     .with_update_rate_hz(30.0);
/// ```
#[derive(Debug, Clone)]
pub struct VuMeterConfig {
    /// Minimum expected level (0.0-1.0)
    pub min_level: f32,
    /// Maximum expected level (0.0-1.0)
    pub max_level: f32,
    /// Update frequency (Hz)
    pub update_rate_hz: f32,
    /// Smoothing factor validation tolerance
    pub smoothing_tolerance: f32,
    /// Maximum time without updates (staleness)
    pub max_stale_ms: u64,
}

impl Default for VuMeterConfig {
    fn default() -> Self {
        Self {
            min_level: 0.0,
            max_level: 1.0,
            update_rate_hz: 30.0,
            smoothing_tolerance: 0.1,
            max_stale_ms: 100,
        }
    }
}

impl VuMeterConfig {
    /// Set minimum expected level
    #[must_use]
    pub fn with_min_level(mut self, level: f32) -> Self {
        self.min_level = level.clamp(0.0, 1.0);
        self
    }

    /// Set maximum expected level
    #[must_use]
    pub fn with_max_level(mut self, level: f32) -> Self {
        self.max_level = level.clamp(0.0, 1.0);
        self
    }

    /// Set expected update rate in Hz
    #[must_use]
    pub fn with_update_rate_hz(mut self, rate: f32) -> Self {
        self.update_rate_hz = rate.max(1.0);
        self
    }

    /// Set staleness threshold
    #[must_use]
    pub fn with_max_stale_ms(mut self, ms: u64) -> Self {
        self.max_stale_ms = ms;
        self
    }

    /// Validate a VU meter sample
    pub fn validate_sample(&self, level: f32) -> Result<(), VuMeterError> {
        if level < 0.0 {
            return Err(VuMeterError::NegativeLevel(level));
        }
        if level > self.max_level + self.smoothing_tolerance {
            return Err(VuMeterError::Clipping(level));
        }
        Ok(())
    }
}

/// VU meter validation error
#[derive(Debug, Clone)]
pub enum VuMeterError {
    /// Level is negative
    NegativeLevel(f32),
    /// Level exceeds maximum (clipping)
    Clipping(f32),
    /// Updates are stale
    Stale {
        /// Last update timestamp
        last_update_ms: u64,
        /// Current timestamp
        current_ms: u64,
    },
    /// Update rate too slow
    SlowUpdateRate {
        /// Measured rate
        measured_hz: f32,
        /// Expected rate
        expected_hz: f32,
    },
    /// Constant value detected (not animating)
    NotAnimating {
        /// Number of samples
        sample_count: usize,
        /// Constant value
        value: f32,
    },
}

impl fmt::Display for VuMeterError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::NegativeLevel(v) => write!(f, "VU meter level is negative: {v}"),
            Self::Clipping(v) => write!(f, "VU meter clipping at: {v}"),
            Self::Stale {
                last_update_ms,
                current_ms,
            } => {
                write!(
                    f,
                    "VU meter stale: last update {}ms ago",
                    current_ms - last_update_ms
                )
            }
            Self::SlowUpdateRate {
                measured_hz,
                expected_hz,
            } => {
                write!(
                    f,
                    "VU meter update rate too slow: {measured_hz:.1}Hz < {expected_hz:.1}Hz"
                )
            }
            Self::NotAnimating {
                sample_count,
                value,
            } => {
                write!(
                    f,
                    "VU meter not animating: {sample_count} samples all at {value}"
                )
            }
        }
    }
}

impl std::error::Error for VuMeterError {}

// =============================================================================
// State Transition Tracking (Section 2.4)
// =============================================================================

/// State transition event with timing
#[derive(Debug, Clone)]
pub struct StateTransition {
    /// Previous state
    pub from: String,
    /// New state
    pub to: String,
    /// Timestamp of transition (ms since start)
    pub timestamp_ms: f64,
    /// Duration in previous state (ms)
    pub duration_ms: f64,
}

/// Partial transcription result
#[derive(Debug, Clone)]
pub struct PartialResult {
    /// Timestamp (ms since start)
    pub timestamp_ms: f64,
    /// Partial text content
    pub text: String,
    /// Whether this is the final result
    pub is_final: bool,
}

/// VU meter sample
#[derive(Debug, Clone)]
pub struct VuMeterSample {
    /// Timestamp (ms since start)
    pub timestamp_ms: f64,
    /// Level (0.0-1.0)
    pub level: f32,
}

// =============================================================================
// Test Execution Stats (Section 5.1 - trueno-zram integration)
// =============================================================================

/// Test execution statistics with compression metrics
///
/// Tracks game state capture efficiency during test runs.
/// Based on trueno-zram compression statistics patterns.
///
/// # Example
/// ```
/// use jugar_probar::validators::TestExecutionStats;
///
/// let mut stats = TestExecutionStats::new();
/// stats.record_state_capture(4096, 1024);
/// stats.record_state_capture(4096, 512); // Same-fill page
///
/// assert!(stats.efficiency() > 0.5);
/// ```
#[derive(Debug, Clone, Default)]
pub struct TestExecutionStats {
    /// Total game states captured
    pub states_captured: u64,
    /// Bytes before compression
    pub bytes_raw: u64,
    /// Bytes after compression
    pub bytes_compressed: u64,
    /// Same-fill pages detected (high compression)
    pub same_fill_pages: u64,
    /// Start time (for throughput calculation)
    start_time: Option<Instant>,
    /// End time (for throughput calculation)
    end_time: Option<Instant>,
}

impl TestExecutionStats {
    /// Create new stats tracker
    #[must_use]
    pub fn new() -> Self {
        Self {
            states_captured: 0,
            bytes_raw: 0,
            bytes_compressed: 0,
            same_fill_pages: 0,
            start_time: None,
            end_time: None,
        }
    }

    /// Start tracking
    pub fn start(&mut self) {
        self.start_time = Some(Instant::now());
    }

    /// Stop tracking
    pub fn stop(&mut self) {
        self.end_time = Some(Instant::now());
    }

    /// Record a state capture
    pub fn record_state_capture(&mut self, raw_bytes: u64, compressed_bytes: u64) {
        self.states_captured += 1;
        self.bytes_raw += raw_bytes;
        self.bytes_compressed += compressed_bytes;

        // Detect same-fill pages (>90% compression = likely uniform data)
        if raw_bytes > 0 && (compressed_bytes as f64 / raw_bytes as f64) < 0.1 {
            self.same_fill_pages += 1;
        }
    }

    /// Calculate compression ratio (raw / compressed)
    #[must_use]
    pub fn compression_ratio(&self) -> f64 {
        if self.bytes_compressed == 0 {
            return 0.0;
        }
        self.bytes_raw as f64 / self.bytes_compressed as f64
    }

    /// Calculate compression efficiency (1 - compressed/raw)
    #[must_use]
    pub fn efficiency(&self) -> f64 {
        if self.bytes_raw == 0 {
            return 0.0;
        }
        1.0 - (self.bytes_compressed as f64 / self.bytes_raw as f64)
    }

    /// Estimate storage savings in MB
    #[must_use]
    pub fn storage_savings_mb(&self) -> f64 {
        (self.bytes_raw.saturating_sub(self.bytes_compressed)) as f64 / 1_000_000.0
    }

    /// Calculate compression throughput (bytes/sec)
    #[must_use]
    pub fn compress_throughput(&self) -> f64 {
        match (self.start_time, self.end_time) {
            (Some(start), Some(end)) => {
                let duration_secs = end.duration_since(start).as_secs_f64();
                if duration_secs > 0.0 {
                    self.bytes_raw as f64 / duration_secs
                } else {
                    0.0
                }
            }
            _ => 0.0,
        }
    }

    /// Get same-fill page ratio
    #[must_use]
    pub fn same_fill_ratio(&self) -> f64 {
        if self.states_captured == 0 {
            return 0.0;
        }
        self.same_fill_pages as f64 / self.states_captured as f64
    }

    /// Reset statistics
    pub fn reset(&mut self) {
        self.states_captured = 0;
        self.bytes_raw = 0;
        self.bytes_compressed = 0;
        self.same_fill_pages = 0;
        self.start_time = None;
        self.end_time = None;
    }
}

// =============================================================================
// Screenshot Content Classifier (Section 5.2)
// =============================================================================

/// Compression algorithm recommendation
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum CompressionAlgorithm {
    /// LZ4 for speed (UI-heavy content)
    Lz4,
    /// Zstd for balanced speed/ratio
    Zstd,
    /// PNG for lossless images
    Png,
    /// RLE for uniform content
    Rle,
}

/// Screenshot content classification for optimal compression
///
/// Based on entropy analysis to determine best compression strategy.
///
/// # Example
/// ```
/// use jugar_probar::validators::ScreenshotContent;
///
/// // Simulate UI-heavy screenshot (low entropy)
/// let pixels: Vec<u8> = vec![255; 1000]; // Uniform white
/// let content = ScreenshotContent::classify(&pixels);
///
/// assert!(matches!(content, ScreenshotContent::Uniform { .. }));
/// ```
#[derive(Debug, Clone)]
pub enum ScreenshotContent {
    /// UI-heavy (text, buttons) - high compressibility
    UiDominated {
        /// Shannon entropy (0.0-8.0 for bytes)
        entropy: f32,
    },
    /// Physics/game world - medium compressibility
    GameWorld {
        /// Shannon entropy
        entropy: f32,
    },
    /// Random/noise - low compressibility
    HighEntropy {
        /// Shannon entropy
        entropy: f32,
    },
    /// Mostly uniform - very high compressibility (same-fill)
    Uniform {
        /// Dominant fill value
        fill_value: u8,
    },
}

impl ScreenshotContent {
    /// Classify screenshot by entropy analysis
    ///
    /// Uses Shannon entropy to determine content type.
    #[must_use]
    pub fn classify(pixels: &[u8]) -> Self {
        if pixels.is_empty() {
            return Self::Uniform { fill_value: 0 };
        }

        // Count byte frequencies
        let mut frequencies = [0u64; 256];
        for &byte in pixels {
            frequencies[byte as usize] += 1;
        }

        // Check for uniform content (>95% same value)
        let total = pixels.len() as f64;
        let (max_idx, max_count) = frequencies
            .iter()
            .enumerate()
            .max_by_key(|(_, &count)| count)
            .map(|(idx, &count)| (idx, count))
            .unwrap_or((0, 0));

        if max_count as f64 / total > 0.95 {
            return Self::Uniform {
                fill_value: max_idx as u8,
            };
        }

        // Calculate Shannon entropy
        let entropy: f32 = frequencies
            .iter()
            .filter(|&&count| count > 0)
            .map(|&count| {
                let p = count as f64 / total;
                -(p * p.log2()) as f32
            })
            .sum();

        // Classify based on entropy thresholds
        if entropy < 3.0 {
            Self::UiDominated { entropy }
        } else if entropy < 6.0 {
            Self::GameWorld { entropy }
        } else {
            Self::HighEntropy { entropy }
        }
    }

    /// Get entropy value
    #[must_use]
    pub fn entropy(&self) -> f32 {
        match self {
            Self::UiDominated { entropy }
            | Self::GameWorld { entropy }
            | Self::HighEntropy { entropy } => *entropy,
            Self::Uniform { .. } => 0.0,
        }
    }

    /// Recommended compression algorithm based on content type
    #[must_use]
    pub fn recommended_algorithm(&self) -> CompressionAlgorithm {
        match self {
            Self::Uniform { .. } => CompressionAlgorithm::Rle,
            Self::UiDominated { .. } => CompressionAlgorithm::Png,
            Self::GameWorld { .. } => CompressionAlgorithm::Zstd,
            Self::HighEntropy { .. } => CompressionAlgorithm::Lz4,
        }
    }

    /// Expected compression ratio hint
    #[must_use]
    pub fn expected_ratio_hint(&self) -> &'static str {
        match self {
            Self::Uniform { .. } => "excellent (>100:1)",
            Self::UiDominated { .. } => "good (5:1 - 20:1)",
            Self::GameWorld { .. } => "moderate (2:1 - 5:1)",
            Self::HighEntropy { .. } => "poor (<2:1)",
        }
    }
}

/// Streaming UX validator for real-time audio/video interfaces
///
/// # Example
/// ```
/// use std::time::Duration;
/// use jugar_probar::validators::{StreamingUxValidator, StreamingMetric};
///
/// let mut validator = StreamingUxValidator::new()
///     .with_max_latency(Duration::from_millis(100))
///     .with_buffer_underrun_threshold(3);
///
/// // Simulate streaming metrics
/// validator.record_metric(StreamingMetric::Latency(Duration::from_millis(50)));
/// validator.record_metric(StreamingMetric::FrameRendered { timestamp: 1000 });
///
/// assert!(validator.validate().is_ok());
/// ```
#[derive(Debug, Clone)]
pub struct StreamingUxValidator {
    /// Maximum acceptable latency
    max_latency: Duration,
    /// Maximum buffer underrun count threshold
    buffer_underrun_threshold: usize,
    /// Maximum consecutive dropped frames
    max_dropped_frames: usize,
    /// Minimum frames per second
    min_fps: f64,
    /// Time-to-first-byte timeout
    ttfb_timeout: Duration,
    /// Recorded metrics
    metrics: Vec<StreamingMetricRecord>,
    /// Buffer underrun count
    buffer_underruns: usize,
    /// Dropped frame count
    dropped_frames: usize,
    /// Frame timestamps for FPS calculation
    frame_times: VecDeque<u64>,
    /// First byte received time
    first_byte_time: Option<Instant>,
    /// Start time
    start_time: Option<Instant>,
    /// State machine state
    state: StreamingState,
    /// State transition history
    state_history: Vec<(StreamingState, Instant)>,
}

/// Streaming metric record with timestamp
#[derive(Debug, Clone)]
pub struct StreamingMetricRecord {
    /// The metric
    pub metric: StreamingMetric,
    /// When recorded
    pub timestamp: Instant,
}

/// Streaming metrics to record
#[derive(Debug, Clone)]
pub enum StreamingMetric {
    /// Latency measurement
    Latency(Duration),
    /// Frame rendered with timestamp
    FrameRendered {
        /// Frame timestamp in milliseconds
        timestamp: u64,
    },
    /// Frame dropped
    FrameDropped,
    /// Buffer underrun occurred
    BufferUnderrun,
    /// First byte received
    FirstByteReceived,
    /// Buffer level percentage
    BufferLevel(f32),
    /// Audio chunk processed
    AudioChunk {
        /// Sample count
        samples: usize,
        /// Sample rate
        sample_rate: u32,
    },
}

/// Streaming state machine states
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum StreamingState {
    /// Initial state
    Idle,
    /// Loading/buffering
    Buffering,
    /// Actively streaming
    Streaming,
    /// Stalled (buffer underrun)
    Stalled,
    /// Error state
    Error,
    /// Completed
    Completed,
}

impl Default for StreamingState {
    fn default() -> Self {
        Self::Idle
    }
}

impl fmt::Display for StreamingState {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Idle => write!(f, "Idle"),
            Self::Buffering => write!(f, "Buffering"),
            Self::Streaming => write!(f, "Streaming"),
            Self::Stalled => write!(f, "Stalled"),
            Self::Error => write!(f, "Error"),
            Self::Completed => write!(f, "Completed"),
        }
    }
}

/// Streaming validation error
#[derive(Debug, Clone)]
pub enum StreamingValidationError {
    /// Latency exceeded threshold
    LatencyExceeded {
        /// Measured latency
        measured: Duration,
        /// Maximum allowed
        max: Duration,
    },
    /// Too many buffer underruns
    BufferUnderrunThreshold {
        /// Number of underruns
        count: usize,
        /// Threshold
        threshold: usize,
    },
    /// Too many dropped frames
    DroppedFrameThreshold {
        /// Number of dropped frames
        count: usize,
        /// Maximum allowed
        max: usize,
    },
    /// FPS below minimum
    FpsBelowMinimum {
        /// Measured FPS
        measured: f64,
        /// Minimum required
        min: f64,
    },
    /// Time to first byte exceeded
    TtfbExceeded {
        /// Measured TTFB
        measured: Duration,
        /// Maximum allowed
        max: Duration,
    },
    /// Invalid state transition
    InvalidStateTransition {
        /// From state
        from: StreamingState,
        /// To state
        to: StreamingState,
    },
    /// State machine ended in error state
    EndedInError,
}

impl fmt::Display for StreamingValidationError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::LatencyExceeded { measured, max } => {
                write!(f, "Latency exceeded: {measured:?} > {max:?} (max allowed)")
            }
            Self::BufferUnderrunThreshold { count, threshold } => {
                write!(
                    f,
                    "Buffer underruns exceeded threshold: {count} > {threshold}"
                )
            }
            Self::DroppedFrameThreshold { count, max } => {
                write!(f, "Dropped frames exceeded: {count} > {max} (max allowed)")
            }
            Self::FpsBelowMinimum { measured, min } => {
                write!(f, "FPS below minimum: {measured:.1} < {min:.1} (required)")
            }
            Self::TtfbExceeded { measured, max } => {
                write!(
                    f,
                    "Time to first byte exceeded: {measured:?} > {max:?} (max allowed)"
                )
            }
            Self::InvalidStateTransition { from, to } => {
                write!(f, "Invalid state transition: {from} -> {to}")
            }
            Self::EndedInError => write!(f, "Streaming ended in error state"),
        }
    }
}

impl std::error::Error for StreamingValidationError {}

impl Default for StreamingUxValidator {
    fn default() -> Self {
        Self::new()
    }
}

impl StreamingUxValidator {
    /// Create a new streaming UX validator with sensible defaults
    #[must_use]
    pub fn new() -> Self {
        Self {
            max_latency: Duration::from_millis(200),
            buffer_underrun_threshold: 5,
            max_dropped_frames: 10,
            min_fps: 24.0,
            ttfb_timeout: Duration::from_secs(3),
            metrics: Vec::new(),
            buffer_underruns: 0,
            dropped_frames: 0,
            frame_times: VecDeque::with_capacity(120),
            first_byte_time: None,
            start_time: None,
            state: StreamingState::Idle,
            state_history: Vec::new(),
        }
    }

    /// Create validator for real-time audio streaming
    #[must_use]
    pub fn for_audio() -> Self {
        Self::new()
            .with_max_latency(Duration::from_millis(100))
            .with_buffer_underrun_threshold(3)
            .with_ttfb_timeout(Duration::from_secs(2))
    }

    /// Create validator for video streaming
    #[must_use]
    pub fn for_video() -> Self {
        Self::new()
            .with_max_latency(Duration::from_millis(500))
            .with_min_fps(30.0)
            .with_max_dropped_frames(5)
    }

    /// Set maximum acceptable latency
    #[must_use]
    pub fn with_max_latency(mut self, latency: Duration) -> Self {
        self.max_latency = latency;
        self
    }

    /// Set buffer underrun threshold
    #[must_use]
    pub fn with_buffer_underrun_threshold(mut self, threshold: usize) -> Self {
        self.buffer_underrun_threshold = threshold;
        self
    }

    /// Set maximum dropped frames
    #[must_use]
    pub fn with_max_dropped_frames(mut self, max: usize) -> Self {
        self.max_dropped_frames = max;
        self
    }

    /// Set minimum FPS
    #[must_use]
    pub fn with_min_fps(mut self, fps: f64) -> Self {
        self.min_fps = fps;
        self
    }

    /// Set time-to-first-byte timeout
    #[must_use]
    pub fn with_ttfb_timeout(mut self, timeout: Duration) -> Self {
        self.ttfb_timeout = timeout;
        self
    }

    /// Start streaming validation
    pub fn start(&mut self) {
        self.start_time = Some(Instant::now());
        self.transition_to(StreamingState::Buffering);
    }

    /// Record a streaming metric
    pub fn record_metric(&mut self, metric: StreamingMetric) {
        let now = Instant::now();

        match &metric {
            StreamingMetric::Latency(latency) => {
                // Latency recorded - check if streaming
                if self.state == StreamingState::Buffering && *latency < self.max_latency {
                    self.transition_to(StreamingState::Streaming);
                }
            }
            StreamingMetric::FrameRendered { timestamp } => {
                self.frame_times.push_back(*timestamp);
                // Keep only last 120 frames (4 seconds at 30fps)
                while self.frame_times.len() > 120 {
                    self.frame_times.pop_front();
                }
                // If streaming, we're healthy
                if self.state == StreamingState::Stalled {
                    self.transition_to(StreamingState::Streaming);
                }
            }
            StreamingMetric::FrameDropped => {
                self.dropped_frames += 1;
            }
            StreamingMetric::BufferUnderrun => {
                self.buffer_underruns += 1;
                if self.state == StreamingState::Streaming {
                    self.transition_to(StreamingState::Stalled);
                }
            }
            StreamingMetric::FirstByteReceived => {
                self.first_byte_time = Some(now);
                if self.state == StreamingState::Idle {
                    self.transition_to(StreamingState::Buffering);
                }
            }
            StreamingMetric::BufferLevel(level) => {
                // Low buffer level indicates potential stall
                if *level < 0.1 && self.state == StreamingState::Streaming {
                    self.transition_to(StreamingState::Stalled);
                } else if *level > 0.3 && self.state == StreamingState::Stalled {
                    self.transition_to(StreamingState::Streaming);
                }
            }
            StreamingMetric::AudioChunk { .. } => {
                // Audio chunk received - mark streaming active
                if self.state == StreamingState::Buffering {
                    self.transition_to(StreamingState::Streaming);
                }
            }
        }

        self.metrics.push(StreamingMetricRecord {
            metric,
            timestamp: now,
        });
    }

    /// Transition to a new state
    fn transition_to(&mut self, new_state: StreamingState) {
        if self.state != new_state {
            self.state_history.push((self.state, Instant::now()));
            self.state = new_state;
        }
    }

    /// Mark streaming as completed
    pub fn complete(&mut self) {
        self.transition_to(StreamingState::Completed);
    }

    /// Mark streaming as errored
    pub fn error(&mut self) {
        self.transition_to(StreamingState::Error);
    }

    /// Get current state
    #[must_use]
    pub fn state(&self) -> StreamingState {
        self.state
    }

    /// Get buffer underrun count
    #[must_use]
    pub fn buffer_underruns(&self) -> usize {
        self.buffer_underruns
    }

    /// Get dropped frame count
    #[must_use]
    pub fn dropped_frames(&self) -> usize {
        self.dropped_frames
    }

    /// Calculate average FPS from recorded frames
    #[must_use]
    pub fn average_fps(&self) -> f64 {
        if self.frame_times.len() < 2 {
            return 0.0;
        }

        let first = *self.frame_times.front().unwrap_or(&0);
        let last = *self.frame_times.back().unwrap_or(&0);
        let duration_ms = last.saturating_sub(first);

        if duration_ms == 0 {
            return 0.0;
        }

        let frame_count = self.frame_times.len() - 1;
        (frame_count as f64 * 1000.0) / duration_ms as f64
    }

    /// Validate all recorded metrics
    ///
    /// # Errors
    /// Returns validation error if any threshold is exceeded.
    pub fn validate(&self) -> Result<StreamingValidationResult, StreamingValidationError> {
        let mut errors = Vec::new();

        // Check latency metrics
        for record in &self.metrics {
            if let StreamingMetric::Latency(latency) = &record.metric {
                if *latency > self.max_latency {
                    errors.push(StreamingValidationError::LatencyExceeded {
                        measured: *latency,
                        max: self.max_latency,
                    });
                }
            }
        }

        // Check buffer underruns
        if self.buffer_underruns > self.buffer_underrun_threshold {
            errors.push(StreamingValidationError::BufferUnderrunThreshold {
                count: self.buffer_underruns,
                threshold: self.buffer_underrun_threshold,
            });
        }

        // Check dropped frames
        if self.dropped_frames > self.max_dropped_frames {
            errors.push(StreamingValidationError::DroppedFrameThreshold {
                count: self.dropped_frames,
                max: self.max_dropped_frames,
            });
        }

        // Check FPS
        let fps = self.average_fps();
        if fps > 0.0 && fps < self.min_fps {
            errors.push(StreamingValidationError::FpsBelowMinimum {
                measured: fps,
                min: self.min_fps,
            });
        }

        // Check TTFB
        if let (Some(start), Some(first_byte)) = (self.start_time, self.first_byte_time) {
            let ttfb = first_byte.duration_since(start);
            if ttfb > self.ttfb_timeout {
                errors.push(StreamingValidationError::TtfbExceeded {
                    measured: ttfb,
                    max: self.ttfb_timeout,
                });
            }
        }

        // Check final state
        if self.state == StreamingState::Error {
            errors.push(StreamingValidationError::EndedInError);
        }

        if errors.is_empty() {
            Ok(StreamingValidationResult {
                buffer_underruns: self.buffer_underruns,
                dropped_frames: self.dropped_frames,
                average_fps: fps,
                max_latency_recorded: self.max_recorded_latency(),
                total_frames: self.frame_times.len(),
            })
        } else {
            Err(errors.remove(0))
        }
    }

    /// Get all validation errors (for comprehensive reporting)
    #[must_use]
    pub fn validate_all(&self) -> Vec<StreamingValidationError> {
        let mut errors = Vec::new();

        for record in &self.metrics {
            if let StreamingMetric::Latency(latency) = &record.metric {
                if *latency > self.max_latency {
                    errors.push(StreamingValidationError::LatencyExceeded {
                        measured: *latency,
                        max: self.max_latency,
                    });
                }
            }
        }

        if self.buffer_underruns > self.buffer_underrun_threshold {
            errors.push(StreamingValidationError::BufferUnderrunThreshold {
                count: self.buffer_underruns,
                threshold: self.buffer_underrun_threshold,
            });
        }

        if self.dropped_frames > self.max_dropped_frames {
            errors.push(StreamingValidationError::DroppedFrameThreshold {
                count: self.dropped_frames,
                max: self.max_dropped_frames,
            });
        }

        let fps = self.average_fps();
        if fps > 0.0 && fps < self.min_fps {
            errors.push(StreamingValidationError::FpsBelowMinimum {
                measured: fps,
                min: self.min_fps,
            });
        }

        if self.state == StreamingState::Error {
            errors.push(StreamingValidationError::EndedInError);
        }

        errors
    }

    /// Get maximum recorded latency
    fn max_recorded_latency(&self) -> Duration {
        self.metrics
            .iter()
            .filter_map(|r| {
                if let StreamingMetric::Latency(l) = &r.metric {
                    Some(*l)
                } else {
                    None
                }
            })
            .max()
            .unwrap_or(Duration::ZERO)
    }

    /// Get state history for debugging
    #[must_use]
    pub fn state_history(&self) -> &[(StreamingState, Instant)] {
        &self.state_history
    }

    /// Reset validator for reuse
    pub fn reset(&mut self) {
        self.metrics.clear();
        self.buffer_underruns = 0;
        self.dropped_frames = 0;
        self.frame_times.clear();
        self.first_byte_time = None;
        self.start_time = None;
        self.state = StreamingState::Idle;
        self.state_history.clear();
    }
}

/// Successful validation result
#[derive(Debug, Clone)]
pub struct StreamingValidationResult {
    /// Number of buffer underruns
    pub buffer_underruns: usize,
    /// Number of dropped frames
    pub dropped_frames: usize,
    /// Average FPS
    pub average_fps: f64,
    /// Maximum latency recorded
    pub max_latency_recorded: Duration,
    /// Total frames processed
    pub total_frames: usize,
}

// CDP-based streaming UX tracking (PROBAR-SPEC-011)
#[cfg(feature = "browser")]
impl StreamingUxValidator {
    /// Track state changes on element via CDP
    ///
    /// Sets up a MutationObserver to watch for text content changes
    /// on the specified element and records state transitions.
    ///
    /// # Errors
    /// Returns error if CDP injection fails or element not found.
    pub async fn track_state_cdp(
        page: &chromiumoxide::Page,
        selector: &str,
    ) -> Result<Self, StreamingValidationError> {
        // Inject MutationObserver to track text changes
        let js = format!(
            r#"
            (function() {{
                window.__probar_state_history = [];
                window.__probar_start_time = performance.now();
                window.__probar_last_state = '';

                const el = document.querySelector('{}');
                if (!el) {{
                    return {{ error: 'Element not found: {}' }};
                }}

                const observer = new MutationObserver((mutations) => {{
                    const newState = el.textContent || el.innerText || '';
                    if (newState !== window.__probar_last_state) {{
                        const now = performance.now();
                        const elapsed = now - window.__probar_start_time;
                        window.__probar_state_history.push({{
                            from: window.__probar_last_state,
                            to: newState,
                            timestamp: elapsed,
                        }});
                        window.__probar_last_state = newState;
                    }}
                }});

                observer.observe(el, {{
                    characterData: true,
                    childList: true,
                    subtree: true
                }});

                window.__probar_state_observer = observer;
                return {{ success: true }};
            }})()
            "#,
            selector, selector
        );

        let _: serde_json::Value = page
            .evaluate(js)
            .await
            .map_err(|_e| StreamingValidationError::InvalidStateTransition {
                from: StreamingState::Idle,
                to: StreamingState::Error,
            })?
            .into_value()
            .map_err(|_| StreamingValidationError::InvalidStateTransition {
                from: StreamingState::Idle,
                to: StreamingState::Error,
            })?;

        Ok(Self::new())
    }

    /// Track VU meter levels via CDP
    ///
    /// Sets up an animation frame loop to sample VU meter values
    /// from the specified element's width, height, or data attribute.
    ///
    /// # Errors
    /// Returns error if CDP injection fails.
    pub async fn track_vu_meter_cdp(
        &mut self,
        page: &chromiumoxide::Page,
        selector: &str,
    ) -> Result<(), StreamingValidationError> {
        let js = format!(
            r#"
            (function() {{
                window.__probar_vu_samples = [];
                window.__probar_vu_start_time = performance.now();

                const el = document.querySelector('{}');
                if (!el) {{
                    return {{ error: 'VU meter element not found: {}' }};
                }}

                function sampleVu() {{
                    const elapsed = performance.now() - window.__probar_vu_start_time;
                    // Try to get level from data attribute, width, or computed style
                    let level = parseFloat(el.dataset.level) || 0;
                    if (!level) {{
                        const style = getComputedStyle(el);
                        const widthPct = parseFloat(style.width) / parseFloat(style.maxWidth || 100);
                        level = isNaN(widthPct) ? 0 : widthPct;
                    }}
                    window.__probar_vu_samples.push([elapsed, level]);

                    if (window.__probar_vu_running) {{
                        requestAnimationFrame(sampleVu);
                    }}
                }}

                window.__probar_vu_running = true;
                requestAnimationFrame(sampleVu);
                return {{ success: true }};
            }})()
            "#,
            selector, selector
        );

        let _: serde_json::Value = page
            .evaluate(js)
            .await
            .map_err(|_| StreamingValidationError::EndedInError)?
            .into_value()
            .map_err(|_| StreamingValidationError::EndedInError)?;

        Ok(())
    }

    /// Track partial transcription results via CDP
    ///
    /// Watches for text content changes on the specified element
    /// and records partial results with timestamps.
    ///
    /// # Errors
    /// Returns error if CDP injection fails.
    pub async fn track_partials_cdp(
        &mut self,
        page: &chromiumoxide::Page,
        selector: &str,
    ) -> Result<(), StreamingValidationError> {
        let js = format!(
            r#"
            (function() {{
                window.__probar_partials = [];
                window.__probar_partials_start = performance.now();
                window.__probar_last_partial = '';

                const el = document.querySelector('{}');
                if (!el) {{
                    return {{ error: 'Partial results element not found: {}' }};
                }}

                const observer = new MutationObserver((mutations) => {{
                    const text = el.textContent || el.innerText || '';
                    if (text !== window.__probar_last_partial) {{
                        const elapsed = performance.now() - window.__probar_partials_start;
                        window.__probar_partials.push([elapsed, text]);
                        window.__probar_last_partial = text;
                    }}
                }});

                observer.observe(el, {{
                    characterData: true,
                    childList: true,
                    subtree: true
                }});

                window.__probar_partials_observer = observer;
                return {{ success: true }};
            }})()
            "#,
            selector, selector
        );

        let _: serde_json::Value = page
            .evaluate(js)
            .await
            .map_err(|_| StreamingValidationError::EndedInError)?
            .into_value()
            .map_err(|_| StreamingValidationError::EndedInError)?;

        Ok(())
    }

    /// Collect state history from browser
    ///
    /// # Errors
    /// Returns error if CDP call fails.
    pub async fn collect_state_history_cdp(
        &self,
        page: &chromiumoxide::Page,
    ) -> Result<Vec<StateTransition>, StreamingValidationError> {
        let js = r#"
            (function() {
                const history = window.__probar_state_history || [];
                return history.map((h, i, arr) => ({
                    from: h.from,
                    to: h.to,
                    timestamp: h.timestamp,
                    duration_ms: i < arr.length - 1 ? arr[i + 1].timestamp - h.timestamp : 0
                }));
            })()
        "#;

        let result: Vec<serde_json::Value> = page
            .evaluate(js)
            .await
            .map_err(|_| StreamingValidationError::EndedInError)?
            .into_value()
            .map_err(|_| StreamingValidationError::EndedInError)?;

        Ok(result
            .into_iter()
            .map(|v| StateTransition {
                from: v["from"].as_str().unwrap_or("").to_string(),
                to: v["to"].as_str().unwrap_or("").to_string(),
                timestamp_ms: v["timestamp"].as_f64().unwrap_or(0.0),
                duration_ms: v["duration_ms"].as_f64().unwrap_or(0.0),
            })
            .collect())
    }

    /// Collect VU meter samples from browser
    ///
    /// # Errors
    /// Returns error if CDP call fails.
    pub async fn collect_vu_samples_cdp(
        &self,
        page: &chromiumoxide::Page,
    ) -> Result<Vec<VuMeterSample>, StreamingValidationError> {
        // Stop sampling
        let _: serde_json::Value = page
            .evaluate("window.__probar_vu_running = false; true")
            .await
            .map_err(|_| StreamingValidationError::EndedInError)?
            .into_value()
            .map_err(|_| StreamingValidationError::EndedInError)?;

        let js = "window.__probar_vu_samples || []";
        let result: Vec<Vec<f64>> = page
            .evaluate(js)
            .await
            .map_err(|_| StreamingValidationError::EndedInError)?
            .into_value()
            .map_err(|_| StreamingValidationError::EndedInError)?;

        Ok(result
            .into_iter()
            .map(|arr| VuMeterSample {
                timestamp_ms: arr.first().copied().unwrap_or(0.0),
                level: arr.get(1).copied().unwrap_or(0.0) as f32,
            })
            .collect())
    }

    /// Collect partial results from browser
    ///
    /// # Errors
    /// Returns error if CDP call fails.
    pub async fn collect_partials_cdp(
        &self,
        page: &chromiumoxide::Page,
    ) -> Result<Vec<PartialResult>, StreamingValidationError> {
        let js = "window.__probar_partials || []";
        let result: Vec<Vec<serde_json::Value>> = page
            .evaluate(js)
            .await
            .map_err(|_| StreamingValidationError::EndedInError)?
            .into_value()
            .map_err(|_| StreamingValidationError::EndedInError)?;

        let partials: Vec<PartialResult> = result
            .into_iter()
            .filter_map(|arr| {
                let ts = arr.first()?.as_f64()?;
                let text = arr.get(1)?.as_str()?.to_string();
                Some(PartialResult {
                    timestamp_ms: ts,
                    text,
                    is_final: false,
                })
            })
            .collect();

        // Mark the last one as final if present
        if partials.is_empty() {
            return Ok(partials);
        }

        let mut result = partials;
        if let Some(last) = result.last_mut() {
            last.is_final = true;
        }
        Ok(result)
    }

    /// Assert state sequence occurred in order
    ///
    /// # Errors
    /// Returns error if sequence was not observed.
    pub async fn assert_state_sequence_cdp(
        &self,
        page: &chromiumoxide::Page,
        expected: &[&str],
    ) -> Result<(), StreamingValidationError> {
        let history = self.collect_state_history_cdp(page).await?;
        let states: Vec<&str> = history.iter().map(|t| t.to.as_str()).collect();

        let mut expected_iter = expected.iter();
        let mut current_expected = expected_iter.next();

        for state in &states {
            if let Some(exp) = current_expected {
                if state == exp {
                    current_expected = expected_iter.next();
                }
            }
        }

        if current_expected.is_some() {
            return Err(StreamingValidationError::InvalidStateTransition {
                from: StreamingState::Idle,
                to: StreamingState::Error,
            });
        }

        Ok(())
    }

    /// Assert VU meter was active during period
    ///
    /// # Errors
    /// Returns error if VU meter was not active for required duration.
    pub async fn assert_vu_meter_active_cdp(
        &self,
        page: &chromiumoxide::Page,
        min_level: f32,
        duration_ms: u64,
    ) -> Result<(), StreamingValidationError> {
        let samples = self.collect_vu_samples_cdp(page).await?;

        let mut active_duration: f64 = 0.0;
        let mut last_ts: Option<f64> = None;

        for sample in &samples {
            if sample.level >= min_level {
                if let Some(prev_ts) = last_ts {
                    active_duration += sample.timestamp_ms - prev_ts;
                }
            }
            last_ts = Some(sample.timestamp_ms);
        }

        if active_duration < duration_ms as f64 {
            return Err(StreamingValidationError::TtfbExceeded {
                measured: Duration::from_millis(active_duration as u64),
                max: Duration::from_millis(duration_ms),
            });
        }

        Ok(())
    }

    /// Assert no UI jank (state updates within threshold)
    ///
    /// # Errors
    /// Returns error if gap between updates exceeds threshold.
    pub async fn assert_no_jank_cdp(
        &self,
        page: &chromiumoxide::Page,
        max_gap_ms: f64,
    ) -> Result<(), StreamingValidationError> {
        let history = self.collect_state_history_cdp(page).await?;

        for transition in &history {
            if transition.duration_ms > max_gap_ms {
                return Err(StreamingValidationError::LatencyExceeded {
                    measured: Duration::from_millis(transition.duration_ms as u64),
                    max: Duration::from_millis(max_gap_ms as u64),
                });
            }
        }

        Ok(())
    }

    /// Assert partial results appeared before final result
    ///
    /// # Errors
    /// Returns error if no partials appeared before final.
    pub async fn assert_partials_before_final_cdp(
        &self,
        page: &chromiumoxide::Page,
    ) -> Result<(), StreamingValidationError> {
        let partials = self.collect_partials_cdp(page).await?;

        // Need at least 2 results (one partial, one final)
        if partials.len() < 2 {
            return Err(StreamingValidationError::EndedInError);
        }

        // Verify there's at least one non-final result before the final
        let non_final_count = partials.iter().filter(|p| !p.is_final).count();
        if non_final_count == 0 {
            return Err(StreamingValidationError::EndedInError);
        }

        Ok(())
    }

    /// Get average state transition time in milliseconds
    ///
    /// # Errors
    /// Returns error if CDP call fails.
    pub async fn avg_transition_time_ms_cdp(
        &self,
        page: &chromiumoxide::Page,
    ) -> Result<f64, StreamingValidationError> {
        let history = self.collect_state_history_cdp(page).await?;

        if history.is_empty() {
            return Ok(0.0);
        }

        let total: f64 = history.iter().map(|t| t.duration_ms).sum();
        Ok(total / history.len() as f64)
    }
}

#[cfg(test)]
#[allow(clippy::unwrap_used, clippy::expect_used)]
mod tests {
    use super::*;

    // ========================================================================
    // H7: Streaming latency monitoring is accurate - Falsification tests
    // ========================================================================

    #[test]
    fn f029_latency_exceeded() {
        // Falsification: Latency above threshold should fail validation
        let mut validator =
            StreamingUxValidator::new().with_max_latency(Duration::from_millis(100));

        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(150)));

        let result = validator.validate();
        assert!(result.is_err());
        let err = result.unwrap_err();
        assert!(matches!(
            err,
            StreamingValidationError::LatencyExceeded { .. }
        ));
    }

    #[test]
    fn f030_latency_acceptable() {
        // Falsification: Latency below threshold should pass
        let mut validator =
            StreamingUxValidator::new().with_max_latency(Duration::from_millis(100));

        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(50)));

        assert!(validator.validate().is_ok());
    }

    #[test]
    fn f031_buffer_underrun_threshold() {
        // Falsification: Too many buffer underruns should fail
        let mut validator = StreamingUxValidator::new().with_buffer_underrun_threshold(2);

        validator.record_metric(StreamingMetric::BufferUnderrun);
        validator.record_metric(StreamingMetric::BufferUnderrun);
        validator.record_metric(StreamingMetric::BufferUnderrun);

        let result = validator.validate();
        assert!(result.is_err());
        assert!(matches!(
            result.unwrap_err(),
            StreamingValidationError::BufferUnderrunThreshold { .. }
        ));
    }

    #[test]
    fn f032_dropped_frames_threshold() {
        // Falsification: Too many dropped frames should fail
        let mut validator = StreamingUxValidator::new().with_max_dropped_frames(2);

        for _ in 0..5 {
            validator.record_metric(StreamingMetric::FrameDropped);
        }

        let result = validator.validate();
        assert!(result.is_err());
        assert!(matches!(
            result.unwrap_err(),
            StreamingValidationError::DroppedFrameThreshold { .. }
        ));
    }

    // ========================================================================
    // H8: State machine transitions are valid - Falsification tests
    // ========================================================================

    #[test]
    fn f033_state_idle_to_buffering() {
        // Falsification: FirstByteReceived should transition Idle -> Buffering
        let mut validator = StreamingUxValidator::new();
        assert_eq!(validator.state(), StreamingState::Idle);

        validator.record_metric(StreamingMetric::FirstByteReceived);
        assert_eq!(validator.state(), StreamingState::Buffering);
    }

    #[test]
    fn f034_state_buffering_to_streaming() {
        // Falsification: Audio chunk should transition Buffering -> Streaming
        let mut validator = StreamingUxValidator::new();
        validator.start();
        assert_eq!(validator.state(), StreamingState::Buffering);

        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });
        assert_eq!(validator.state(), StreamingState::Streaming);
    }

    #[test]
    fn f035_state_streaming_to_stalled() {
        // Falsification: Buffer underrun should transition Streaming -> Stalled
        let mut validator = StreamingUxValidator::new();
        validator.start();
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });
        assert_eq!(validator.state(), StreamingState::Streaming);

        validator.record_metric(StreamingMetric::BufferUnderrun);
        assert_eq!(validator.state(), StreamingState::Stalled);
    }

    #[test]
    fn f036_state_recovery_from_stalled() {
        // Falsification: Frame rendered should recover Stalled -> Streaming
        let mut validator = StreamingUxValidator::new();
        validator.start();
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });
        validator.record_metric(StreamingMetric::BufferUnderrun);
        assert_eq!(validator.state(), StreamingState::Stalled);

        validator.record_metric(StreamingMetric::FrameRendered { timestamp: 1000 });
        assert_eq!(validator.state(), StreamingState::Streaming);
    }

    // ========================================================================
    // H9: FPS calculation is accurate - Falsification tests
    // ========================================================================

    #[test]
    fn f037_fps_calculation() {
        // Falsification: FPS should be calculated correctly
        let mut validator = StreamingUxValidator::new();

        // Simulate 30fps for 1 second
        for i in 0..31 {
            validator.record_metric(StreamingMetric::FrameRendered {
                timestamp: i * 33, // ~30fps
            });
        }

        let fps = validator.average_fps();
        // Should be approximately 30fps
        assert!((fps - 30.0).abs() < 1.0, "FPS was {fps}, expected ~30");
    }

    #[test]
    fn f038_fps_below_minimum() {
        // Falsification: Low FPS should fail validation
        let mut validator = StreamingUxValidator::new().with_min_fps(30.0);

        // Simulate 15fps for 1 second
        for i in 0..16 {
            validator.record_metric(StreamingMetric::FrameRendered {
                timestamp: i * 66, // ~15fps
            });
        }

        let result = validator.validate();
        assert!(result.is_err());
        assert!(matches!(
            result.unwrap_err(),
            StreamingValidationError::FpsBelowMinimum { .. }
        ));
    }

    // ========================================================================
    // Unit tests for core functionality
    // ========================================================================

    #[test]
    fn test_default_validator() {
        let validator = StreamingUxValidator::new();
        assert_eq!(validator.state(), StreamingState::Idle);
        assert_eq!(validator.buffer_underruns(), 0);
        assert_eq!(validator.dropped_frames(), 0);
    }

    #[test]
    fn test_audio_preset() {
        let validator = StreamingUxValidator::for_audio();
        assert_eq!(validator.max_latency, Duration::from_millis(100));
        assert_eq!(validator.buffer_underrun_threshold, 3);
    }

    #[test]
    fn test_video_preset() {
        let validator = StreamingUxValidator::for_video();
        assert_eq!(validator.max_latency, Duration::from_millis(500));
        assert!((validator.min_fps - 30.0).abs() < f64::EPSILON);
    }

    #[test]
    fn test_complete_transition() {
        let mut validator = StreamingUxValidator::new();
        validator.complete();
        assert_eq!(validator.state(), StreamingState::Completed);
    }

    #[test]
    fn test_error_transition() {
        let mut validator = StreamingUxValidator::new();
        validator.error();
        assert_eq!(validator.state(), StreamingState::Error);
        assert!(validator.validate().is_err());
    }

    #[test]
    fn test_reset() {
        let mut validator = StreamingUxValidator::new();
        validator.start();
        validator.record_metric(StreamingMetric::BufferUnderrun);
        validator.record_metric(StreamingMetric::FrameDropped);

        validator.reset();
        assert_eq!(validator.state(), StreamingState::Idle);
        assert_eq!(validator.buffer_underruns(), 0);
        assert_eq!(validator.dropped_frames(), 0);
    }

    #[test]
    fn test_validate_all_errors() {
        let mut validator = StreamingUxValidator::new()
            .with_max_latency(Duration::from_millis(50))
            .with_buffer_underrun_threshold(1);

        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(100)));
        validator.record_metric(StreamingMetric::BufferUnderrun);
        validator.record_metric(StreamingMetric::BufferUnderrun);

        let errors = validator.validate_all();
        assert!(errors.len() >= 2);
    }

    #[test]
    fn test_state_history() {
        let mut validator = StreamingUxValidator::new();
        validator.start();
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });

        let history = validator.state_history();
        assert!(!history.is_empty());
        assert_eq!(history[0].0, StreamingState::Idle);
    }

    #[test]
    fn test_buffer_level_transitions() {
        let mut validator = StreamingUxValidator::new();
        validator.start();
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });
        assert_eq!(validator.state(), StreamingState::Streaming);

        // Low buffer level should stall
        validator.record_metric(StreamingMetric::BufferLevel(0.05));
        assert_eq!(validator.state(), StreamingState::Stalled);

        // Buffer recovery should resume streaming
        validator.record_metric(StreamingMetric::BufferLevel(0.5));
        assert_eq!(validator.state(), StreamingState::Streaming);
    }

    #[test]
    fn test_streaming_state_display() {
        assert_eq!(format!("{}", StreamingState::Idle), "Idle");
        assert_eq!(format!("{}", StreamingState::Streaming), "Streaming");
        assert_eq!(format!("{}", StreamingState::Stalled), "Stalled");
    }

    // ========================================================================
    // H10: VU Meter validation is accurate - Falsification tests
    // ========================================================================

    #[test]
    fn f039_vu_meter_negative_level_rejected() {
        // Falsification: Negative levels should be rejected
        let config = VuMeterConfig::default();
        let result = config.validate_sample(-0.5);
        assert!(result.is_err());
        assert!(matches!(
            result.unwrap_err(),
            VuMeterError::NegativeLevel(_)
        ));
    }

    #[test]
    fn f040_vu_meter_clipping_detected() {
        // Falsification: Level above max (with tolerance) should be clipping
        let config = VuMeterConfig::default().with_max_level(1.0);
        // Level 1.5 exceeds 1.0 + 0.1 tolerance
        let result = config.validate_sample(1.5);
        assert!(result.is_err());
        assert!(matches!(result.unwrap_err(), VuMeterError::Clipping(_)));
    }

    #[test]
    fn f041_vu_meter_valid_level_accepted() {
        // Falsification: Valid level should pass
        let config = VuMeterConfig::default();
        assert!(config.validate_sample(0.5).is_ok());
        assert!(config.validate_sample(0.0).is_ok());
        assert!(config.validate_sample(1.0).is_ok());
    }

    #[test]
    fn f042_vu_meter_config_builder() {
        // Falsification: Builder methods should work correctly
        let config = VuMeterConfig::default()
            .with_min_level(0.1)
            .with_max_level(0.9)
            .with_update_rate_hz(60.0)
            .with_max_stale_ms(50);

        assert!((config.min_level - 0.1).abs() < f32::EPSILON);
        assert!((config.max_level - 0.9).abs() < f32::EPSILON);
        assert!((config.update_rate_hz - 60.0).abs() < f32::EPSILON);
        assert_eq!(config.max_stale_ms, 50);
    }

    #[test]
    fn f043_vu_meter_level_clamping() {
        // Falsification: Out-of-range levels should be clamped in config
        let config = VuMeterConfig::default()
            .with_min_level(-5.0)
            .with_max_level(10.0);

        // Clamped to 0.0-1.0 range
        assert!((config.min_level - 0.0).abs() < f32::EPSILON);
        assert!((config.max_level - 1.0).abs() < f32::EPSILON);
    }

    #[test]
    fn f044_vu_meter_min_update_rate() {
        // Falsification: Update rate should have minimum of 1.0 Hz
        let config = VuMeterConfig::default().with_update_rate_hz(0.1);

        assert!((config.update_rate_hz - 1.0).abs() < f32::EPSILON);
    }

    #[test]
    fn f045_vu_meter_error_display() {
        // Falsification: Error messages should be informative
        let negative = VuMeterError::NegativeLevel(-0.5);
        assert!(negative.to_string().contains("negative"));

        let clipping = VuMeterError::Clipping(1.5);
        assert!(clipping.to_string().contains("clipping"));

        let stale = VuMeterError::Stale {
            last_update_ms: 100,
            current_ms: 300,
        };
        assert!(stale.to_string().contains("stale"));

        let slow = VuMeterError::SlowUpdateRate {
            measured_hz: 10.0,
            expected_hz: 30.0,
        };
        assert!(slow.to_string().contains("slow"));

        let not_animating = VuMeterError::NotAnimating {
            sample_count: 10,
            value: 0.5,
        };
        assert!(not_animating.to_string().contains("not animating"));
    }

    #[test]
    fn f046_state_transition_tracking() {
        // Falsification: State transitions should be properly structured
        let transition = StateTransition {
            from: "Idle".to_string(),
            to: "Recording".to_string(),
            timestamp_ms: 1000.0,
            duration_ms: 500.0,
        };

        assert_eq!(transition.from, "Idle");
        assert_eq!(transition.to, "Recording");
        assert!((transition.timestamp_ms - 1000.0).abs() < f64::EPSILON);
        assert!((transition.duration_ms - 500.0).abs() < f64::EPSILON);
    }

    #[test]
    fn f047_partial_result_tracking() {
        // Falsification: Partial results should track interim transcriptions
        let partial = PartialResult {
            timestamp_ms: 1500.0,
            text: "Hello wo".to_string(),
            is_final: false,
        };

        assert!(!partial.is_final);
        assert_eq!(partial.text, "Hello wo");

        let final_result = PartialResult {
            timestamp_ms: 2000.0,
            text: "Hello world".to_string(),
            is_final: true,
        };

        assert!(final_result.is_final);
    }

    #[test]
    fn f048_vu_meter_sample_tracking() {
        // Falsification: VU meter samples should track level over time
        let samples = vec![
            VuMeterSample {
                timestamp_ms: 0.0,
                level: 0.1,
            },
            VuMeterSample {
                timestamp_ms: 33.3,
                level: 0.3,
            },
            VuMeterSample {
                timestamp_ms: 66.6,
                level: 0.5,
            },
            VuMeterSample {
                timestamp_ms: 100.0,
                level: 0.4,
            },
        ];

        // Calculate average level
        let avg: f32 = samples.iter().map(|s| s.level).sum::<f32>() / samples.len() as f32;
        assert!((avg - 0.325).abs() < 0.01);

        // Check time span
        let duration = samples.last().unwrap().timestamp_ms - samples.first().unwrap().timestamp_ms;
        assert!((duration - 100.0).abs() < f64::EPSILON);
    }

    // ========================================================================
    // H11: Test Execution Stats are accurate - Falsification tests (Section 5.1)
    // ========================================================================

    #[test]
    fn f049_test_execution_stats_creation() {
        // Falsification: New stats should be zero-initialized
        let stats = TestExecutionStats::new();
        assert_eq!(stats.states_captured, 0);
        assert_eq!(stats.bytes_raw, 0);
        assert_eq!(stats.bytes_compressed, 0);
        assert_eq!(stats.same_fill_pages, 0);
    }

    #[test]
    fn f050_test_execution_stats_recording() {
        // Falsification: Stats should correctly record captures
        let mut stats = TestExecutionStats::new();
        stats.record_state_capture(4096, 1024);
        stats.record_state_capture(4096, 2048);

        assert_eq!(stats.states_captured, 2);
        assert_eq!(stats.bytes_raw, 8192);
        assert_eq!(stats.bytes_compressed, 3072);
    }

    #[test]
    fn f051_test_execution_stats_compression_ratio() {
        // Falsification: Compression ratio should be raw/compressed
        let mut stats = TestExecutionStats::new();
        stats.record_state_capture(4000, 1000);

        let ratio = stats.compression_ratio();
        assert!((ratio - 4.0).abs() < 0.01);
    }

    #[test]
    fn f052_test_execution_stats_efficiency() {
        // Falsification: Efficiency should be 1 - (compressed/raw)
        let mut stats = TestExecutionStats::new();
        stats.record_state_capture(1000, 250); // 75% efficiency

        let efficiency = stats.efficiency();
        assert!((efficiency - 0.75).abs() < 0.01);
    }

    #[test]
    fn f053_test_execution_stats_storage_savings() {
        // Falsification: Storage savings should be in MB
        let mut stats = TestExecutionStats::new();
        stats.record_state_capture(5_000_000, 1_000_000); // 4MB saved

        let savings = stats.storage_savings_mb();
        assert!((savings - 4.0).abs() < 0.01);
    }

    #[test]
    fn f054_test_execution_stats_same_fill_detection() {
        // Falsification: >90% compression should be detected as same-fill
        let mut stats = TestExecutionStats::new();
        stats.record_state_capture(4096, 100); // 97.5% compression - same-fill
        stats.record_state_capture(4096, 1024); // 75% compression - not same-fill

        assert_eq!(stats.same_fill_pages, 1);
        assert!((stats.same_fill_ratio() - 0.5).abs() < 0.01);
    }

    #[test]
    fn f055_test_execution_stats_reset() {
        // Falsification: Reset should clear all stats
        let mut stats = TestExecutionStats::new();
        stats.record_state_capture(4096, 1024);
        stats.reset();

        assert_eq!(stats.states_captured, 0);
        assert_eq!(stats.bytes_raw, 0);
        assert_eq!(stats.bytes_compressed, 0);
    }

    #[test]
    fn f056_test_execution_stats_edge_cases() {
        // Falsification: Edge cases should not panic
        let mut stats = TestExecutionStats::new();

        // Zero bytes
        assert!((stats.compression_ratio() - 0.0).abs() < f64::EPSILON);
        assert!((stats.efficiency() - 0.0).abs() < f64::EPSILON);
        assert!((stats.same_fill_ratio() - 0.0).abs() < f64::EPSILON);

        // Record with zero compressed
        stats.record_state_capture(1000, 0);
        assert!((stats.compression_ratio() - 0.0).abs() < f64::EPSILON); // Avoid division by zero
    }

    // ========================================================================
    // H12: Screenshot content classification is accurate - Falsification tests (Section 5.2)
    // ========================================================================

    #[test]
    fn f057_screenshot_content_uniform_detection() {
        // Falsification: >95% same value should be classified as Uniform
        let pixels: Vec<u8> = vec![255; 1000];
        let content = ScreenshotContent::classify(&pixels);

        assert!(matches!(
            content,
            ScreenshotContent::Uniform { fill_value: 255 }
        ));
        assert!((content.entropy() - 0.0).abs() < f32::EPSILON);
    }

    #[test]
    fn f058_screenshot_content_ui_dominated() {
        // Falsification: Low entropy (<3.0) should be UI-dominated
        // Simulate mostly uniform with some variation (like UI text)
        let mut pixels = vec![255u8; 900]; // 90% white
        pixels.extend(vec![0u8; 50]); // 5% black
        pixels.extend(vec![128u8; 50]); // 5% gray

        let content = ScreenshotContent::classify(&pixels);
        // This should not be Uniform since it's <95% same value
        // And should have low entropy
        assert!(matches!(
            content,
            ScreenshotContent::UiDominated { .. } | ScreenshotContent::Uniform { .. }
        ));
    }

    #[test]
    fn f059_screenshot_content_high_entropy() {
        // Falsification: Random data should be classified as HighEntropy
        // Create pseudo-random looking data
        let pixels: Vec<u8> = (0..1000).map(|i| ((i * 127 + 37) % 256) as u8).collect();
        let content = ScreenshotContent::classify(&pixels);

        // Should be GameWorld or HighEntropy depending on actual entropy
        assert!(matches!(
            content,
            ScreenshotContent::GameWorld { .. } | ScreenshotContent::HighEntropy { .. }
        ));
    }

    #[test]
    fn f060_screenshot_content_compression_algorithm() {
        // Falsification: Compression algorithm should match content type
        let uniform = ScreenshotContent::Uniform { fill_value: 0 };
        assert_eq!(uniform.recommended_algorithm(), CompressionAlgorithm::Rle);

        let ui = ScreenshotContent::UiDominated { entropy: 2.0 };
        assert_eq!(ui.recommended_algorithm(), CompressionAlgorithm::Png);

        let game = ScreenshotContent::GameWorld { entropy: 4.5 };
        assert_eq!(game.recommended_algorithm(), CompressionAlgorithm::Zstd);

        let high = ScreenshotContent::HighEntropy { entropy: 7.0 };
        assert_eq!(high.recommended_algorithm(), CompressionAlgorithm::Lz4);
    }

    #[test]
    fn f061_screenshot_content_ratio_hints() {
        // Falsification: Ratio hints should describe compression expectations
        let uniform = ScreenshotContent::Uniform { fill_value: 0 };
        assert!(uniform.expected_ratio_hint().contains("excellent"));

        let ui = ScreenshotContent::UiDominated { entropy: 2.0 };
        assert!(ui.expected_ratio_hint().contains("good"));

        let game = ScreenshotContent::GameWorld { entropy: 4.5 };
        assert!(game.expected_ratio_hint().contains("moderate"));

        let high = ScreenshotContent::HighEntropy { entropy: 7.0 };
        assert!(high.expected_ratio_hint().contains("poor"));
    }

    #[test]
    fn f062_screenshot_content_empty_input() {
        // Falsification: Empty input should be handled gracefully
        let content = ScreenshotContent::classify(&[]);
        assert!(matches!(
            content,
            ScreenshotContent::Uniform { fill_value: 0 }
        ));
    }

    #[test]
    fn f063_screenshot_content_entropy_extraction() {
        // Falsification: Entropy should be extractable from all variants
        let variants = [
            ScreenshotContent::UiDominated { entropy: 1.5 },
            ScreenshotContent::GameWorld { entropy: 4.0 },
            ScreenshotContent::HighEntropy { entropy: 7.5 },
            ScreenshotContent::Uniform { fill_value: 128 },
        ];

        let entropies: Vec<f32> = variants.iter().map(|v| v.entropy()).collect();
        assert!((entropies[0] - 1.5).abs() < f32::EPSILON);
        assert!((entropies[1] - 4.0).abs() < f32::EPSILON);
        assert!((entropies[2] - 7.5).abs() < f32::EPSILON);
        assert!((entropies[3] - 0.0).abs() < f32::EPSILON); // Uniform has 0 entropy
    }

    // ========================================================================
    // Additional coverage tests for validators.rs
    // ========================================================================

    #[test]
    fn test_execution_stats_start_stop_throughput() {
        // Test start/stop timing and throughput calculation
        let mut stats = TestExecutionStats::new();
        stats.start();

        // Record some captures
        stats.record_state_capture(1_000_000, 100_000);
        stats.record_state_capture(1_000_000, 100_000);

        stats.stop();

        // Throughput should be > 0 after recording data
        let throughput = stats.compress_throughput();
        // May be 0 if test runs too fast, but shouldn't panic
        assert!(throughput >= 0.0);
    }

    #[test]
    fn test_execution_stats_throughput_no_timing() {
        // Test throughput without start/stop
        let mut stats = TestExecutionStats::new();
        stats.record_state_capture(1000, 100);

        // Should return 0 when no timing is set
        assert!((stats.compress_throughput() - 0.0).abs() < f64::EPSILON);
    }

    #[test]
    fn test_execution_stats_throughput_start_only() {
        // Test throughput with only start (no stop)
        let mut stats = TestExecutionStats::new();
        stats.start();
        stats.record_state_capture(1000, 100);

        // Should return 0 when end time not set
        assert!((stats.compress_throughput() - 0.0).abs() < f64::EPSILON);
    }

    #[test]
    fn test_streaming_validation_error_display() {
        // Test Display implementations for all error variants
        let latency_err = StreamingValidationError::LatencyExceeded {
            measured: Duration::from_millis(500),
            max: Duration::from_millis(100),
        };
        assert!(latency_err.to_string().contains("exceeded"));

        let underrun_err = StreamingValidationError::BufferUnderrunThreshold {
            count: 10,
            threshold: 5,
        };
        assert!(underrun_err.to_string().contains("Buffer underruns"));

        let dropped_err = StreamingValidationError::DroppedFrameThreshold { count: 20, max: 10 };
        assert!(dropped_err.to_string().contains("Dropped frames"));

        let fps_err = StreamingValidationError::FpsBelowMinimum {
            measured: 15.0,
            min: 30.0,
        };
        assert!(fps_err.to_string().contains("FPS below"));

        let ttfb_err = StreamingValidationError::TtfbExceeded {
            measured: Duration::from_secs(5),
            max: Duration::from_secs(2),
        };
        assert!(ttfb_err.to_string().contains("first byte"));

        let transition_err = StreamingValidationError::InvalidStateTransition {
            from: StreamingState::Idle,
            to: StreamingState::Completed,
        };
        assert!(transition_err.to_string().contains("Invalid state"));

        let error_err = StreamingValidationError::EndedInError;
        assert!(error_err.to_string().contains("error state"));
    }

    #[test]
    fn test_streaming_state_default() {
        let state: StreamingState = Default::default();
        assert_eq!(state, StreamingState::Idle);
    }

    #[test]
    fn test_streaming_state_display_all_variants() {
        assert_eq!(format!("{}", StreamingState::Idle), "Idle");
        assert_eq!(format!("{}", StreamingState::Buffering), "Buffering");
        assert_eq!(format!("{}", StreamingState::Streaming), "Streaming");
        assert_eq!(format!("{}", StreamingState::Stalled), "Stalled");
        assert_eq!(format!("{}", StreamingState::Error), "Error");
        assert_eq!(format!("{}", StreamingState::Completed), "Completed");
    }

    #[test]
    fn test_streaming_metric_record_creation() {
        let record = StreamingMetricRecord {
            metric: StreamingMetric::BufferUnderrun,
            timestamp: Instant::now(),
        };
        assert!(matches!(record.metric, StreamingMetric::BufferUnderrun));
    }

    #[test]
    fn test_streaming_ux_validator_default() {
        let validator: StreamingUxValidator = Default::default();
        assert_eq!(validator.state(), StreamingState::Idle);
    }

    #[test]
    fn test_ttfb_validation() {
        let mut validator =
            StreamingUxValidator::new().with_ttfb_timeout(Duration::from_millis(100));

        // Start and wait for first byte
        validator.start();

        // Simulate waiting too long before first byte
        std::thread::sleep(Duration::from_millis(150));

        // Record first byte
        validator.record_metric(StreamingMetric::FirstByteReceived);

        let result = validator.validate();
        // TTFB should be exceeded
        assert!(result.is_err());
        if let Err(err) = result {
            assert!(matches!(err, StreamingValidationError::TtfbExceeded { .. }));
        }
    }

    #[test]
    fn test_ttfb_validation_success() {
        let mut validator = StreamingUxValidator::new().with_ttfb_timeout(Duration::from_secs(5));

        // Start and immediately receive first byte
        validator.start();
        validator.record_metric(StreamingMetric::FirstByteReceived);

        // Other metrics to make it valid
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });

        let result = validator.validate();
        assert!(result.is_ok());
    }

    #[test]
    fn test_compression_algorithm_enum() {
        // Ensure all variants are distinct
        assert_ne!(CompressionAlgorithm::Lz4, CompressionAlgorithm::Zstd);
        assert_ne!(CompressionAlgorithm::Zstd, CompressionAlgorithm::Png);
        assert_ne!(CompressionAlgorithm::Png, CompressionAlgorithm::Rle);
    }

    #[test]
    fn test_vu_meter_config_debug() {
        let config = VuMeterConfig::default();
        let debug_str = format!("{:?}", config);
        assert!(debug_str.contains("VuMeterConfig"));
    }

    #[test]
    fn test_state_transition_debug() {
        let transition = StateTransition {
            from: "Idle".to_string(),
            to: "Recording".to_string(),
            timestamp_ms: 1000.0,
            duration_ms: 500.0,
        };
        let debug_str = format!("{:?}", transition);
        assert!(debug_str.contains("StateTransition"));
    }

    #[test]
    fn test_partial_result_debug() {
        let partial = PartialResult {
            timestamp_ms: 1500.0,
            text: "Hello".to_string(),
            is_final: false,
        };
        let debug_str = format!("{:?}", partial);
        assert!(debug_str.contains("PartialResult"));
    }

    #[test]
    fn test_vu_meter_sample_debug() {
        let sample = VuMeterSample {
            timestamp_ms: 100.0,
            level: 0.5,
        };
        let debug_str = format!("{:?}", sample);
        assert!(debug_str.contains("VuMeterSample"));
    }

    #[test]
    fn test_test_execution_stats_debug() {
        let stats = TestExecutionStats::new();
        let debug_str = format!("{:?}", stats);
        assert!(debug_str.contains("TestExecutionStats"));
    }

    #[test]
    fn test_screenshot_content_debug() {
        let content = ScreenshotContent::UiDominated { entropy: 2.0 };
        let debug_str = format!("{:?}", content);
        assert!(debug_str.contains("UiDominated"));
    }

    #[test]
    fn test_streaming_metric_debug() {
        let metric = StreamingMetric::Latency(Duration::from_millis(50));
        let debug_str = format!("{:?}", metric);
        assert!(debug_str.contains("Latency"));
    }

    #[test]
    fn test_streaming_validation_error_as_error() {
        // Test std::error::Error implementation
        let err = StreamingValidationError::EndedInError;
        let _: &dyn std::error::Error = &err;
    }

    #[test]
    fn test_vu_meter_error_as_error() {
        // Test std::error::Error implementation
        let err = VuMeterError::NegativeLevel(-0.5);
        let _: &dyn std::error::Error = &err;
    }

    #[test]
    fn test_streaming_metric_all_variants() {
        // Ensure all variants can be created
        let metrics = vec![
            StreamingMetric::Latency(Duration::from_millis(50)),
            StreamingMetric::FrameRendered { timestamp: 1000 },
            StreamingMetric::FrameDropped,
            StreamingMetric::BufferUnderrun,
            StreamingMetric::FirstByteReceived,
            StreamingMetric::BufferLevel(0.5),
            StreamingMetric::AudioChunk {
                samples: 1024,
                sample_rate: 16000,
            },
        ];

        assert_eq!(metrics.len(), 7);
    }

    #[test]
    fn test_streaming_ux_validator_clone() {
        let validator = StreamingUxValidator::new()
            .with_max_latency(Duration::from_millis(100))
            .with_buffer_underrun_threshold(3);

        let cloned = validator;
        assert_eq!(cloned.state(), StreamingState::Idle);
    }

    #[test]
    fn test_test_execution_stats_clone() {
        let mut stats = TestExecutionStats::new();
        stats.record_state_capture(1000, 100);

        let cloned = stats.clone();
        assert_eq!(cloned.states_captured, 1);
    }

    #[test]
    fn test_vu_meter_config_clone() {
        let config = VuMeterConfig::default().with_min_level(0.2);
        let cloned = config;
        assert!((cloned.min_level - 0.2).abs() < f32::EPSILON);
    }

    #[test]
    fn test_state_transition_clone() {
        let transition = StateTransition {
            from: "Idle".to_string(),
            to: "Recording".to_string(),
            timestamp_ms: 1000.0,
            duration_ms: 500.0,
        };
        let cloned = transition;
        assert_eq!(cloned.from, "Idle");
    }

    // Additional coverage tests

    #[test]
    fn test_vu_meter_stale_error_display() {
        let err = VuMeterError::Stale {
            last_update_ms: 100,
            current_ms: 300,
        };
        let display = format!("{}", err);
        assert!(display.contains("stale"));
        assert!(display.contains("200ms"));
    }

    #[test]
    fn test_vu_meter_slow_update_rate_error_display() {
        let err = VuMeterError::SlowUpdateRate {
            measured_hz: 15.0,
            expected_hz: 30.0,
        };
        let display = format!("{}", err);
        assert!(display.contains("15.0Hz"));
        assert!(display.contains("30.0Hz"));
    }

    #[test]
    fn test_vu_meter_not_animating_error_display() {
        let err = VuMeterError::NotAnimating {
            sample_count: 100,
            value: 0.5,
        };
        let display = format!("{}", err);
        assert!(display.contains("100 samples"));
        assert!(display.contains("0.5"));
    }

    #[test]
    fn test_screenshot_content_game_world() {
        // Create medium entropy data
        let mut pixels = Vec::with_capacity(1000);
        for i in 0..1000 {
            pixels.push((i % 64) as u8); // Moderate variation
        }
        let content = ScreenshotContent::classify(&pixels);
        // With 64 unique values, entropy should be ~6 bits
        match content {
            ScreenshotContent::GameWorld { entropy } => {
                assert!((3.0..6.0).contains(&entropy));
            }
            ScreenshotContent::HighEntropy { entropy } => {
                // Also acceptable for this pattern
                assert!(entropy >= 6.0);
            }
            _ => {}
        }
    }

    #[test]
    fn test_streaming_validation_error_invalid_transition() {
        let err = StreamingValidationError::InvalidStateTransition {
            from: StreamingState::Idle,
            to: StreamingState::Streaming,
        };
        let display = format!("{}", err);
        assert!(display.contains("Invalid state transition"));
        assert!(display.contains("Idle"));
        assert!(display.contains("Streaming"));
    }

    #[test]
    fn test_streaming_latency_transition() {
        let mut validator = StreamingUxValidator::new();
        validator.start();
        assert_eq!(validator.state(), StreamingState::Buffering);

        // Record good latency - should transition to Streaming
        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(10)));
        assert_eq!(validator.state(), StreamingState::Streaming);
    }

    #[test]
    fn test_streaming_buffer_level() {
        let mut validator = StreamingUxValidator::new();
        validator.start();

        // Buffer level should be recorded
        validator.record_metric(StreamingMetric::BufferLevel(0.75));
        assert_eq!(validator.state(), StreamingState::Buffering);
    }

    #[test]
    fn test_streaming_frame_times_overflow() {
        let mut validator = StreamingUxValidator::new();
        validator.start();
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });

        // Add more than 120 frames to test the overflow handling
        for i in 0..150 {
            validator.record_metric(StreamingMetric::FrameRendered { timestamp: i * 33 });
        }

        // Should have capped at 120 frames
        let fps = validator.average_fps();
        assert!(fps > 0.0);
    }

    #[test]
    fn test_streaming_metrics_all_variants_coverage() {
        let mut validator = StreamingUxValidator::new();
        validator.start();

        // Cover all metric variants
        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(50)));
        validator.record_metric(StreamingMetric::FrameRendered { timestamp: 0 });
        validator.record_metric(StreamingMetric::FrameDropped);
        validator.record_metric(StreamingMetric::BufferUnderrun);
        validator.record_metric(StreamingMetric::FirstByteReceived);
        validator.record_metric(StreamingMetric::BufferLevel(0.5));
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });

        assert!(validator.dropped_frames() >= 1);
        assert!(validator.buffer_underruns() >= 1);
    }

    #[test]
    fn test_max_recorded_latency() {
        let mut validator = StreamingUxValidator::new();
        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(50)));
        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(100)));
        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(75)));

        // Access the validate method which uses max_recorded_latency
        let result = validator.validate();
        assert!(result.is_ok());
    }

    #[test]
    fn test_validate_all_with_fps_error() {
        let mut validator = StreamingUxValidator::new()
            .with_min_fps(60.0)
            .with_max_dropped_frames(0);

        // Add some slow frames
        for i in 0..10 {
            validator.record_metric(StreamingMetric::FrameRendered {
                timestamp: i * 100, // 10fps
            });
        }
        validator.record_metric(StreamingMetric::FrameDropped);

        let errors = validator.validate_all();
        assert!(!errors.is_empty());
    }

    #[test]
    fn test_screenshot_content_entropy_boundaries() {
        // Test UI-dominated (entropy < 3.0)
        let mut pixels = Vec::with_capacity(1000);
        for i in 0..1000 {
            pixels.push((i % 4) as u8); // Only 4 unique values = low entropy
        }
        let content = ScreenshotContent::classify(&pixels);
        // Other classifications possible
        if let ScreenshotContent::UiDominated { entropy } = content {
            assert!(entropy < 3.0);
        }
    }

    #[test]
    fn test_test_execution_stats_default() {
        let stats: TestExecutionStats = Default::default();
        assert_eq!(stats.states_captured, 0);
    }

    #[test]
    fn test_streaming_validation_result_success() {
        let mut validator = StreamingUxValidator::new();
        validator.start();
        validator.record_metric(StreamingMetric::FirstByteReceived);
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });

        // Add enough frames for good FPS
        for i in 0..60 {
            validator.record_metric(StreamingMetric::FrameRendered { timestamp: i * 33 });
        }

        validator.complete();

        let result = validator.validate();
        assert!(result.is_ok());
        if let Ok(result) = result {
            assert!(result.max_latency_recorded >= Duration::ZERO);
            assert!(result.average_fps >= 0.0);
        }
    }

    #[test]
    fn test_partial_result_clone() {
        let result = PartialResult {
            timestamp_ms: 100.0,
            text: "test".to_string(),
            is_final: false,
        };
        let cloned = result;
        assert_eq!(cloned.text, "test");
    }

    #[test]
    fn test_vu_meter_sample_clone() {
        let sample = VuMeterSample {
            timestamp_ms: 100.0,
            level: 0.5,
        };
        let cloned = sample;
        assert!((cloned.level - 0.5).abs() < f32::EPSILON);
    }

    #[test]
    fn test_streaming_metric_record_clone() {
        let record = StreamingMetricRecord {
            metric: StreamingMetric::BufferLevel(0.5),
            timestamp: Instant::now(),
        };
        let cloned = record;
        assert!(matches!(cloned.metric, StreamingMetric::BufferLevel(..)));
    }

    #[test]
    fn test_streaming_validation_error_clone() {
        let err = StreamingValidationError::LatencyExceeded {
            measured: Duration::from_millis(150),
            max: Duration::from_millis(100),
        };
        let cloned = err;
        assert!(matches!(
            cloned,
            StreamingValidationError::LatencyExceeded { .. }
        ));
    }

    #[test]
    fn test_vu_meter_error_clone() {
        let err = VuMeterError::Clipping(1.5);
        let cloned = err;
        assert!(matches!(cloned, VuMeterError::Clipping(..)));
    }

    // ========================================================================
    // Additional comprehensive tests for 95%+ coverage
    // ========================================================================

    #[test]
    fn test_average_fps_with_zero_duration() {
        let mut validator = StreamingUxValidator::new();
        // Add frames with same timestamp - zero duration
        validator.record_metric(StreamingMetric::FrameRendered { timestamp: 100 });
        validator.record_metric(StreamingMetric::FrameRendered { timestamp: 100 });

        // Should return 0.0 when duration is 0
        assert!((validator.average_fps() - 0.0).abs() < f64::EPSILON);
    }

    #[test]
    fn test_average_fps_single_frame() {
        let mut validator = StreamingUxValidator::new();
        // Only one frame - not enough to calculate FPS
        validator.record_metric(StreamingMetric::FrameRendered { timestamp: 100 });

        assert!((validator.average_fps() - 0.0).abs() < f64::EPSILON);
    }

    #[test]
    fn test_streaming_validation_result_fields() {
        let mut validator = StreamingUxValidator::new()
            .with_max_latency(Duration::from_secs(10))
            .with_buffer_underrun_threshold(100)
            .with_max_dropped_frames(100)
            .with_min_fps(1.0);

        validator.start();
        validator.record_metric(StreamingMetric::FirstByteReceived);
        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(50)));

        // Add frames for FPS
        for i in 0..60 {
            validator.record_metric(StreamingMetric::FrameRendered { timestamp: i * 16 });
        }

        let result = validator.validate().unwrap();
        assert_eq!(result.buffer_underruns, 0);
        assert_eq!(result.dropped_frames, 0);
        assert!(result.average_fps > 0.0);
        assert!(result.total_frames > 0);
        assert!(result.max_latency_recorded >= Duration::ZERO);
    }

    #[test]
    fn test_max_recorded_latency_empty() {
        let validator = StreamingUxValidator::new();
        // No latency metrics recorded - should use max_recorded_latency internally
        let result = validator.validate();
        assert!(result.is_ok());
    }

    #[test]
    fn test_compression_ratio_with_zero_raw() {
        let mut stats = TestExecutionStats::new();
        // Record with 0 raw bytes
        stats.bytes_raw = 0;
        stats.bytes_compressed = 100;
        // compression_ratio should handle this edge case
        assert!((stats.compression_ratio() - 0.0).abs() < f64::EPSILON);
    }

    #[test]
    fn test_throughput_with_zero_duration() {
        let mut stats = TestExecutionStats::new();
        stats.start();
        stats.record_state_capture(1000, 100);
        // Stop immediately - very short duration
        stats.stop();

        // Should not panic even with very small duration
        let throughput = stats.compress_throughput();
        assert!(throughput >= 0.0);
    }

    #[test]
    fn test_vu_meter_error_stale_clone() {
        let err = VuMeterError::Stale {
            last_update_ms: 100,
            current_ms: 200,
        };
        let cloned = err;
        assert!(matches!(
            cloned,
            VuMeterError::Stale {
                last_update_ms: 100,
                current_ms: 200,
            }
        ));
    }

    #[test]
    fn test_vu_meter_error_slow_update_rate_clone() {
        let err = VuMeterError::SlowUpdateRate {
            measured_hz: 15.0,
            expected_hz: 30.0,
        };
        let cloned = err;
        match cloned {
            VuMeterError::SlowUpdateRate {
                measured_hz,
                expected_hz,
            } => {
                assert!((measured_hz - 15.0).abs() < f32::EPSILON);
                assert!((expected_hz - 30.0).abs() < f32::EPSILON);
            }
            _ => panic!("Expected SlowUpdateRate"),
        }
    }

    #[test]
    fn test_vu_meter_error_not_animating_clone() {
        let err = VuMeterError::NotAnimating {
            sample_count: 10,
            value: 0.5,
        };
        let cloned = err;
        match cloned {
            VuMeterError::NotAnimating {
                sample_count,
                value,
            } => {
                assert_eq!(sample_count, 10);
                assert!((value - 0.5).abs() < f32::EPSILON);
            }
            _ => panic!("Expected NotAnimating"),
        }
    }

    #[test]
    fn test_streaming_validation_error_all_clone_variants() {
        // Test all error variants clone correctly
        let errors: Vec<StreamingValidationError> = vec![
            StreamingValidationError::LatencyExceeded {
                measured: Duration::from_millis(200),
                max: Duration::from_millis(100),
            },
            StreamingValidationError::BufferUnderrunThreshold {
                count: 10,
                threshold: 5,
            },
            StreamingValidationError::DroppedFrameThreshold { count: 20, max: 10 },
            StreamingValidationError::FpsBelowMinimum {
                measured: 15.0,
                min: 30.0,
            },
            StreamingValidationError::TtfbExceeded {
                measured: Duration::from_secs(5),
                max: Duration::from_secs(2),
            },
            StreamingValidationError::InvalidStateTransition {
                from: StreamingState::Idle,
                to: StreamingState::Completed,
            },
            StreamingValidationError::EndedInError,
        ];

        for err in errors {
            let cloned = err.clone();
            // Verify toString works on cloned
            let _ = cloned.to_string();
        }
    }

    #[test]
    fn test_streaming_metric_clone_all_variants() {
        let metrics = vec![
            StreamingMetric::Latency(Duration::from_millis(100)),
            StreamingMetric::FrameRendered { timestamp: 1000 },
            StreamingMetric::FrameDropped,
            StreamingMetric::BufferUnderrun,
            StreamingMetric::FirstByteReceived,
            StreamingMetric::BufferLevel(0.75),
            StreamingMetric::AudioChunk {
                samples: 2048,
                sample_rate: 44100,
            },
        ];

        for metric in metrics {
            let cloned = metric.clone();
            let _ = format!("{:?}", cloned);
        }
    }

    #[test]
    fn test_buffer_level_no_transition_when_not_streaming() {
        let mut validator = StreamingUxValidator::new();
        // Not started, not streaming
        validator.record_metric(StreamingMetric::BufferLevel(0.05));
        assert_eq!(validator.state(), StreamingState::Idle);

        // Buffer recovery when not stalled
        validator.record_metric(StreamingMetric::BufferLevel(0.5));
        assert_eq!(validator.state(), StreamingState::Idle);
    }

    #[test]
    fn test_latency_no_transition_when_exceeds_max() {
        let mut validator = StreamingUxValidator::new().with_max_latency(Duration::from_millis(50));
        validator.start();
        assert_eq!(validator.state(), StreamingState::Buffering);

        // High latency should not transition to streaming
        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(100)));
        assert_eq!(validator.state(), StreamingState::Buffering);
    }

    #[test]
    fn test_frame_rendered_no_transition_when_not_stalled() {
        let mut validator = StreamingUxValidator::new();
        // In Idle state
        validator.record_metric(StreamingMetric::FrameRendered { timestamp: 100 });
        assert_eq!(validator.state(), StreamingState::Idle);

        // In Buffering state
        validator.start();
        validator.record_metric(StreamingMetric::FrameRendered { timestamp: 200 });
        assert_eq!(validator.state(), StreamingState::Buffering);
    }

    #[test]
    fn test_audio_chunk_no_transition_when_not_buffering() {
        let mut validator = StreamingUxValidator::new();
        // In Idle state - should not transition
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });
        assert_eq!(validator.state(), StreamingState::Idle);

        // In Streaming state - should stay streaming
        validator.start();
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });
        assert_eq!(validator.state(), StreamingState::Streaming);
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });
        assert_eq!(validator.state(), StreamingState::Streaming);
    }

    #[test]
    fn test_first_byte_no_transition_when_not_idle() {
        let mut validator = StreamingUxValidator::new();
        validator.start(); // Now in Buffering
        validator.record_metric(StreamingMetric::FirstByteReceived);
        assert_eq!(validator.state(), StreamingState::Buffering);
    }

    #[test]
    fn test_buffer_underrun_no_transition_when_not_streaming() {
        let mut validator = StreamingUxValidator::new();
        // In Idle state
        validator.record_metric(StreamingMetric::BufferUnderrun);
        assert_eq!(validator.state(), StreamingState::Idle);
        assert_eq!(validator.buffer_underruns(), 1);

        // In Buffering state
        validator.start();
        validator.record_metric(StreamingMetric::BufferUnderrun);
        assert_eq!(validator.state(), StreamingState::Buffering);
        assert_eq!(validator.buffer_underruns(), 2);
    }

    #[test]
    fn test_transition_to_same_state() {
        let mut validator = StreamingUxValidator::new();
        validator.start();
        let history_len = validator.state_history().len();

        // Try to transition to current state - should not add to history
        validator.record_metric(StreamingMetric::BufferLevel(0.5)); // Does nothing in Buffering
        assert_eq!(validator.state_history().len(), history_len);
    }

    #[test]
    fn test_screenshot_content_single_byte() {
        // Edge case: single byte input
        let content = ScreenshotContent::classify(&[128]);
        assert!(matches!(
            content,
            ScreenshotContent::Uniform { fill_value: 128 }
        ));
    }

    #[test]
    fn test_screenshot_content_two_bytes_same() {
        let content = ScreenshotContent::classify(&[42, 42]);
        assert!(matches!(
            content,
            ScreenshotContent::Uniform { fill_value: 42 }
        ));
    }

    #[test]
    fn test_screenshot_content_near_uniform_threshold() {
        // 94% same value - should NOT be uniform (threshold is 95%)
        let mut pixels = vec![255u8; 94];
        pixels.extend(vec![0u8; 6]);
        let content = ScreenshotContent::classify(&pixels);
        assert!(!matches!(content, ScreenshotContent::Uniform { .. }));
    }

    #[test]
    fn test_screenshot_content_exactly_at_uniform_threshold() {
        // 96% same value - should be uniform (> 95%)
        let mut pixels = vec![255u8; 96];
        pixels.extend(vec![0u8; 4]);
        let content = ScreenshotContent::classify(&pixels);
        assert!(matches!(
            content,
            ScreenshotContent::Uniform { fill_value: 255 }
        ));
    }

    #[test]
    fn test_screenshot_content_entropy_at_boundary_3() {
        // Create data with entropy around 3.0 (UI vs GameWorld boundary)
        let mut pixels = Vec::new();
        // 8 unique values, equally distributed = log2(8) = 3 bits entropy
        for _ in 0..125 {
            for v in 0u8..8u8 {
                pixels.push(v);
            }
        }
        let content = ScreenshotContent::classify(&pixels);
        // Could be either UI or GameWorld depending on exact calculation
        let entropy = content.entropy();
        assert!((2.5..=3.5).contains(&entropy));
    }

    #[test]
    fn test_screenshot_content_entropy_at_boundary_6() {
        // Create data with entropy around 6.0 (GameWorld vs HighEntropy boundary)
        let mut pixels = Vec::new();
        // 64 unique values = log2(64) = 6 bits entropy
        for _ in 0..16 {
            for v in 0u8..64u8 {
                pixels.push(v);
            }
        }
        let content = ScreenshotContent::classify(&pixels);
        let entropy = content.entropy();
        assert!((5.5..=6.5).contains(&entropy));
    }

    #[test]
    fn test_screenshot_content_maximum_entropy() {
        // Create data with maximum entropy - all 256 values equally distributed
        let mut pixels = Vec::new();
        for _ in 0..4 {
            for v in 0u8..=255u8 {
                pixels.push(v);
            }
        }
        let content = ScreenshotContent::classify(&pixels);
        assert!(matches!(content, ScreenshotContent::HighEntropy { .. }));
        assert!(content.entropy() > 7.0);
    }

    #[test]
    fn test_validate_multiple_latency_exceeded() {
        let mut validator = StreamingUxValidator::new().with_max_latency(Duration::from_millis(50));

        // Multiple latency violations
        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(100)));
        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(150)));
        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(200)));

        let errors = validator.validate_all();
        assert_eq!(errors.len(), 3);
        for err in errors {
            assert!(matches!(
                err,
                StreamingValidationError::LatencyExceeded { .. }
            ));
        }
    }

    #[test]
    fn test_streaming_validation_result_debug() {
        let result = StreamingValidationResult {
            buffer_underruns: 2,
            dropped_frames: 5,
            average_fps: 30.0,
            max_latency_recorded: Duration::from_millis(100),
            total_frames: 1000,
        };
        let debug = format!("{:?}", result);
        assert!(debug.contains("StreamingValidationResult"));
        assert!(debug.contains("buffer_underruns"));
    }

    #[test]
    fn test_streaming_validation_result_clone() {
        let result = StreamingValidationResult {
            buffer_underruns: 3,
            dropped_frames: 7,
            average_fps: 60.0,
            max_latency_recorded: Duration::from_millis(50),
            total_frames: 2000,
        };
        let cloned = result;
        assert_eq!(cloned.buffer_underruns, 3);
        assert_eq!(cloned.dropped_frames, 7);
        assert!((cloned.average_fps - 60.0).abs() < f64::EPSILON);
        assert_eq!(cloned.max_latency_recorded, Duration::from_millis(50));
        assert_eq!(cloned.total_frames, 2000);
    }

    #[test]
    fn test_vu_meter_config_smoothing_tolerance() {
        let config = VuMeterConfig {
            min_level: 0.0,
            max_level: 1.0,
            update_rate_hz: 30.0,
            smoothing_tolerance: 0.2,
            max_stale_ms: 100,
        };

        // Level at max + tolerance should pass
        assert!(config.validate_sample(1.19).is_ok());

        // Level beyond max + tolerance should fail
        assert!(config.validate_sample(1.21).is_err());
    }

    #[test]
    fn test_compression_algorithm_debug() {
        let algos = [
            CompressionAlgorithm::Lz4,
            CompressionAlgorithm::Zstd,
            CompressionAlgorithm::Png,
            CompressionAlgorithm::Rle,
        ];
        for algo in algos {
            let debug = format!("{:?}", algo);
            assert!(!debug.is_empty());
        }
    }

    #[test]
    fn test_compression_algorithm_copy() {
        let algo = CompressionAlgorithm::Lz4;
        let copied = algo;
        assert_eq!(algo, copied);
    }

    #[test]
    fn test_test_execution_stats_large_values() {
        let mut stats = TestExecutionStats::new();
        stats.record_state_capture(u64::MAX / 2, u64::MAX / 4);

        // Should handle large values without overflow
        let ratio = stats.compression_ratio();
        assert!(ratio > 0.0);

        let efficiency = stats.efficiency();
        assert!(efficiency > 0.0 && efficiency < 1.0);
    }

    #[test]
    fn test_storage_savings_small_values() {
        let mut stats = TestExecutionStats::new();
        stats.record_state_capture(500_000, 400_000); // 0.1 MB saved

        let savings = stats.storage_savings_mb();
        assert!((savings - 0.1).abs() < 0.01);
    }

    #[test]
    fn test_storage_savings_compressed_larger_than_raw() {
        let mut stats = TestExecutionStats::new();
        // Edge case: compressed somehow larger than raw (saturating_sub handles this)
        stats.bytes_raw = 100;
        stats.bytes_compressed = 200;

        let savings = stats.storage_savings_mb();
        assert!((savings - 0.0).abs() < f64::EPSILON);
    }

    #[test]
    fn test_same_fill_exactly_at_threshold() {
        let mut stats = TestExecutionStats::new();
        // Exactly 10% compression ratio - boundary case
        stats.record_state_capture(1000, 100);
        // 10% is not < 10%, so should not count as same-fill
        assert_eq!(stats.same_fill_pages, 0);

        // Just under 10%
        stats.record_state_capture(1000, 99);
        assert_eq!(stats.same_fill_pages, 1);
    }

    #[test]
    fn test_streaming_ux_validator_debug() {
        let validator = StreamingUxValidator::new();
        let debug = format!("{:?}", validator);
        assert!(debug.contains("StreamingUxValidator"));
    }

    #[test]
    fn test_streaming_metric_record_debug() {
        let record = StreamingMetricRecord {
            metric: StreamingMetric::FrameDropped,
            timestamp: Instant::now(),
        };
        let debug = format!("{:?}", record);
        assert!(debug.contains("StreamingMetricRecord"));
    }

    #[test]
    fn test_validate_all_empty_metrics() {
        let validator = StreamingUxValidator::new();
        let errors = validator.validate_all();
        assert!(errors.is_empty());
    }

    #[test]
    fn test_validate_with_error_state() {
        let mut validator = StreamingUxValidator::new();
        validator.error();

        let result = validator.validate();
        assert!(result.is_err());
        assert!(matches!(
            result.unwrap_err(),
            StreamingValidationError::EndedInError
        ));
    }

    #[test]
    fn test_validate_all_multiple_error_types() {
        let mut validator = StreamingUxValidator::new()
            .with_max_latency(Duration::from_millis(10))
            .with_buffer_underrun_threshold(0)
            .with_max_dropped_frames(0)
            .with_min_fps(100.0);

        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(50)));
        validator.record_metric(StreamingMetric::BufferUnderrun);
        validator.record_metric(StreamingMetric::FrameDropped);

        // Add slow frames for FPS error
        for i in 0..5 {
            validator.record_metric(StreamingMetric::FrameRendered {
                timestamp: i * 500, // 2 fps
            });
        }

        validator.error();

        let errors = validator.validate_all();
        // Should have: latency, underrun, dropped frames, fps, ended in error
        assert!(errors.len() >= 4);
    }

    #[test]
    fn test_vu_meter_error_negative_level_value() {
        let config = VuMeterConfig::default();
        let result = config.validate_sample(-10.5);
        match result {
            Err(VuMeterError::NegativeLevel(v)) => {
                assert!((v - (-10.5)).abs() < f32::EPSILON);
            }
            _ => panic!("Expected NegativeLevel error"),
        }
    }

    #[test]
    fn test_vu_meter_error_clipping_value() {
        let config = VuMeterConfig::default().with_max_level(0.5);
        let result = config.validate_sample(2.0);
        match result {
            Err(VuMeterError::Clipping(v)) => {
                assert!((v - 2.0).abs() < f32::EPSILON);
            }
            _ => panic!("Expected Clipping error"),
        }
    }

    #[test]
    fn test_streaming_state_hash() {
        use std::collections::HashSet;
        let mut set = HashSet::new();
        set.insert(StreamingState::Idle);
        set.insert(StreamingState::Buffering);
        set.insert(StreamingState::Streaming);
        set.insert(StreamingState::Stalled);
        set.insert(StreamingState::Error);
        set.insert(StreamingState::Completed);

        assert_eq!(set.len(), 6);
        assert!(set.contains(&StreamingState::Idle));
    }

    #[test]
    fn test_screenshot_content_clone() {
        let contents = vec![
            ScreenshotContent::Uniform { fill_value: 128 },
            ScreenshotContent::UiDominated { entropy: 2.5 },
            ScreenshotContent::GameWorld { entropy: 4.5 },
            ScreenshotContent::HighEntropy { entropy: 7.0 },
        ];

        for content in contents {
            let cloned = content.clone();
            assert!((cloned.entropy() - content.entropy()).abs() < f32::EPSILON);
        }
    }

    #[test]
    fn test_test_execution_stats_all_fields() {
        let mut stats = TestExecutionStats::new();
        stats.start();
        stats.record_state_capture(1000, 100);
        stats.record_state_capture(2000, 50); // same-fill
        stats.stop();

        assert_eq!(stats.states_captured, 2);
        assert_eq!(stats.bytes_raw, 3000);
        assert_eq!(stats.bytes_compressed, 150);
        assert_eq!(stats.same_fill_pages, 1);
    }

    #[test]
    fn test_frame_times_exactly_120() {
        let mut validator = StreamingUxValidator::new();
        // Add exactly 120 frames
        for i in 0..120 {
            validator.record_metric(StreamingMetric::FrameRendered { timestamp: i * 16 });
        }
        assert!(validator.average_fps() > 0.0);
    }

    #[test]
    fn test_frame_times_121() {
        let mut validator = StreamingUxValidator::new();
        // Add 121 frames - should cap at 120
        for i in 0..121 {
            validator.record_metric(StreamingMetric::FrameRendered { timestamp: i * 16 });
        }
        // The oldest frame should be removed
        assert!(validator.average_fps() > 0.0);
    }

    #[test]
    fn test_state_transition_fields_access() {
        let transition = StateTransition {
            from: "State1".to_string(),
            to: "State2".to_string(),
            timestamp_ms: 12345.67,
            duration_ms: 890.12,
        };

        assert_eq!(transition.from.as_str(), "State1");
        assert_eq!(transition.to.as_str(), "State2");
        assert!((transition.timestamp_ms - 12345.67).abs() < f64::EPSILON);
        assert!((transition.duration_ms - 890.12).abs() < f64::EPSILON);
    }

    #[test]
    fn test_partial_result_fields_access() {
        let partial = PartialResult {
            timestamp_ms: 999.99,
            text: "Hello World".to_string(),
            is_final: true,
        };

        assert!((partial.timestamp_ms - 999.99).abs() < f64::EPSILON);
        assert_eq!(partial.text.as_str(), "Hello World");
        assert!(partial.is_final);
    }

    #[test]
    fn test_vu_meter_sample_fields_access() {
        let sample = VuMeterSample {
            timestamp_ms: 1234.5,
            level: 0.789,
        };

        assert!((sample.timestamp_ms - 1234.5).abs() < f64::EPSILON);
        assert!((sample.level - 0.789).abs() < f32::EPSILON);
    }

    #[test]
    fn test_streaming_metric_record_fields_access() {
        let timestamp = Instant::now();
        let record = StreamingMetricRecord {
            metric: StreamingMetric::BufferLevel(0.42),
            timestamp,
        };

        assert!(matches!(record.metric, StreamingMetric::BufferLevel(..)));
        assert_eq!(record.timestamp, timestamp);
    }

    #[test]
    fn test_validate_returns_first_error() {
        let mut validator = StreamingUxValidator::new()
            .with_max_latency(Duration::from_millis(10))
            .with_buffer_underrun_threshold(0);

        // Record latency error first (in order)
        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(50)));
        validator.record_metric(StreamingMetric::BufferUnderrun);

        let result = validator.validate();
        assert!(result.is_err());
        // Should return latency error (first in check order)
        assert!(matches!(
            result.unwrap_err(),
            StreamingValidationError::LatencyExceeded { .. }
        ));
    }

    #[test]
    fn test_validate_fps_error_only_when_positive() {
        let mut validator = StreamingUxValidator::new().with_min_fps(100.0);

        // No frames at all - fps is 0, should not trigger fps error
        let result = validator.validate();
        assert!(result.is_ok());

        // Add one frame - fps is still 0
        validator.record_metric(StreamingMetric::FrameRendered { timestamp: 0 });
        let result = validator.validate();
        assert!(result.is_ok());
    }

    #[test]
    fn test_buffer_level_recovery_threshold() {
        let mut validator = StreamingUxValidator::new();
        validator.start();
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });
        assert_eq!(validator.state(), StreamingState::Streaming);

        // Low buffer - should stall
        validator.record_metric(StreamingMetric::BufferLevel(0.05));
        assert_eq!(validator.state(), StreamingState::Stalled);

        // Buffer at exactly 0.3 - should NOT recover (threshold is > 0.3)
        validator.record_metric(StreamingMetric::BufferLevel(0.3));
        assert_eq!(validator.state(), StreamingState::Stalled);

        // Buffer above 0.3 - should recover
        validator.record_metric(StreamingMetric::BufferLevel(0.31));
        assert_eq!(validator.state(), StreamingState::Streaming);
    }

    #[test]
    fn test_buffer_level_stall_threshold() {
        let mut validator = StreamingUxValidator::new();
        validator.start();
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });
        assert_eq!(validator.state(), StreamingState::Streaming);

        // Buffer at exactly 0.1 - should NOT stall (threshold is < 0.1)
        validator.record_metric(StreamingMetric::BufferLevel(0.1));
        assert_eq!(validator.state(), StreamingState::Streaming);

        // Buffer below 0.1 - should stall
        validator.record_metric(StreamingMetric::BufferLevel(0.09));
        assert_eq!(validator.state(), StreamingState::Stalled);
    }

    // ========================================================================
    // Additional tests for 95%+ coverage - Edge cases and branches
    // ========================================================================

    #[test]
    fn test_vu_meter_config_default_values() {
        let config = VuMeterConfig::default();
        assert!((config.min_level - 0.0).abs() < f32::EPSILON);
        assert!((config.max_level - 1.0).abs() < f32::EPSILON);
        assert!((config.update_rate_hz - 30.0).abs() < f32::EPSILON);
        assert!((config.smoothing_tolerance - 0.1).abs() < f32::EPSILON);
        assert_eq!(config.max_stale_ms, 100);
    }

    #[test]
    fn test_vu_meter_error_display_all_variants() {
        // NegativeLevel
        let err = VuMeterError::NegativeLevel(-0.25);
        let display = format!("{}", err);
        assert!(display.contains("-0.25"));
        assert!(display.contains("negative"));

        // Clipping
        let err = VuMeterError::Clipping(1.75);
        let display = format!("{}", err);
        assert!(display.contains("1.75"));
        assert!(display.contains("clipping"));

        // Stale
        let err = VuMeterError::Stale {
            last_update_ms: 50,
            current_ms: 250,
        };
        let display = format!("{}", err);
        assert!(display.contains("200ms"));

        // SlowUpdateRate
        let err = VuMeterError::SlowUpdateRate {
            measured_hz: 20.0,
            expected_hz: 60.0,
        };
        let display = format!("{}", err);
        assert!(display.contains("20.0Hz"));
        assert!(display.contains("60.0Hz"));

        // NotAnimating
        let err = VuMeterError::NotAnimating {
            sample_count: 50,
            value: 0.75,
        };
        let display = format!("{}", err);
        assert!(display.contains("50 samples"));
        assert!(display.contains("0.75"));
    }

    #[test]
    fn test_streaming_validation_error_display_all_variants() {
        let err = StreamingValidationError::LatencyExceeded {
            measured: Duration::from_millis(300),
            max: Duration::from_millis(100),
        };
        assert!(err.to_string().contains("300"));

        let err = StreamingValidationError::BufferUnderrunThreshold {
            count: 15,
            threshold: 5,
        };
        assert!(err.to_string().contains("15"));
        assert!(err.to_string().contains('5'));

        let err = StreamingValidationError::DroppedFrameThreshold { count: 25, max: 10 };
        assert!(err.to_string().contains("25"));
        assert!(err.to_string().contains("10"));

        let err = StreamingValidationError::FpsBelowMinimum {
            measured: 20.5,
            min: 60.0,
        };
        assert!(err.to_string().contains("20.5"));
        assert!(err.to_string().contains("60.0"));

        let err = StreamingValidationError::TtfbExceeded {
            measured: Duration::from_secs(10),
            max: Duration::from_secs(3),
        };
        let display = err.to_string();
        assert!(display.contains("first byte"));

        let err = StreamingValidationError::InvalidStateTransition {
            from: StreamingState::Buffering,
            to: StreamingState::Completed,
        };
        let display = err.to_string();
        assert!(display.contains("Buffering"));
        assert!(display.contains("Completed"));

        let err = StreamingValidationError::EndedInError;
        assert!(err.to_string().contains("error state"));
    }

    #[test]
    fn test_streaming_state_display_coverage() {
        // Test all StreamingState Display implementations
        assert_eq!(format!("{}", StreamingState::Idle), "Idle");
        assert_eq!(format!("{}", StreamingState::Buffering), "Buffering");
        assert_eq!(format!("{}", StreamingState::Streaming), "Streaming");
        assert_eq!(format!("{}", StreamingState::Stalled), "Stalled");
        assert_eq!(format!("{}", StreamingState::Error), "Error");
        assert_eq!(format!("{}", StreamingState::Completed), "Completed");
    }

    #[test]
    fn test_test_execution_stats_zero_raw_bytes() {
        let stats = TestExecutionStats::new();
        // Zero raw bytes should not panic and return 0 efficiency
        assert!((stats.efficiency() - 0.0).abs() < f64::EPSILON);
    }

    #[test]
    fn test_test_execution_stats_zero_compressed_bytes() {
        let mut stats = TestExecutionStats::new();
        stats.bytes_raw = 1000;
        stats.bytes_compressed = 0;
        // Zero compressed bytes should return 0 ratio (avoid div by zero)
        assert!((stats.compression_ratio() - 0.0).abs() < f64::EPSILON);
    }

    #[test]
    fn test_test_execution_stats_zero_states_captured() {
        let stats = TestExecutionStats::new();
        // Zero states should return 0 same_fill_ratio
        assert!((stats.same_fill_ratio() - 0.0).abs() < f64::EPSILON);
    }

    #[test]
    fn test_test_execution_stats_throughput_no_start() {
        let mut stats = TestExecutionStats::new();
        stats.stop();
        stats.record_state_capture(1000, 100);
        // No start time should return 0 throughput
        assert!((stats.compress_throughput() - 0.0).abs() < f64::EPSILON);
    }

    #[test]
    fn test_test_execution_stats_throughput_only_end() {
        let mut stats = TestExecutionStats::new();
        stats.stop();
        // Only end time, no start - should return 0 throughput
        assert!((stats.compress_throughput() - 0.0).abs() < f64::EPSILON);
    }

    #[test]
    fn test_test_execution_stats_same_fill_with_zero_raw() {
        let mut stats = TestExecutionStats::new();
        // Edge case: raw_bytes is 0, should not count as same-fill
        stats.record_state_capture(0, 0);
        assert_eq!(stats.same_fill_pages, 0);
    }

    #[test]
    fn test_screenshot_content_classify_single_pixel() {
        // Edge case: single pixel
        let content = ScreenshotContent::classify(&[42]);
        assert!(matches!(
            content,
            ScreenshotContent::Uniform { fill_value: 42 }
        ));
    }

    #[test]
    fn test_screenshot_content_all_different_values() {
        // All 256 different values - maximum entropy
        let pixels: Vec<u8> = (0..=255).collect();
        let content = ScreenshotContent::classify(&pixels);
        assert!(matches!(content, ScreenshotContent::HighEntropy { .. }));
        // Should have 8 bits of entropy
        assert!(content.entropy() > 7.5);
    }

    #[test]
    fn test_screenshot_content_entropy_method_uniform() {
        let content = ScreenshotContent::Uniform { fill_value: 200 };
        assert!((content.entropy() - 0.0).abs() < f32::EPSILON);
    }

    #[test]
    fn test_screenshot_content_recommended_algorithm_all() {
        assert_eq!(
            ScreenshotContent::Uniform { fill_value: 0 }.recommended_algorithm(),
            CompressionAlgorithm::Rle
        );
        assert_eq!(
            ScreenshotContent::UiDominated { entropy: 2.0 }.recommended_algorithm(),
            CompressionAlgorithm::Png
        );
        assert_eq!(
            ScreenshotContent::GameWorld { entropy: 4.5 }.recommended_algorithm(),
            CompressionAlgorithm::Zstd
        );
        assert_eq!(
            ScreenshotContent::HighEntropy { entropy: 7.0 }.recommended_algorithm(),
            CompressionAlgorithm::Lz4
        );
    }

    #[test]
    fn test_screenshot_content_expected_ratio_hint_all() {
        assert!(ScreenshotContent::Uniform { fill_value: 0 }
            .expected_ratio_hint()
            .contains("excellent"));
        assert!(ScreenshotContent::UiDominated { entropy: 2.0 }
            .expected_ratio_hint()
            .contains("good"));
        assert!(ScreenshotContent::GameWorld { entropy: 4.5 }
            .expected_ratio_hint()
            .contains("moderate"));
        assert!(ScreenshotContent::HighEntropy { entropy: 7.0 }
            .expected_ratio_hint()
            .contains("poor"));
    }

    #[test]
    fn test_streaming_ux_validator_builder_chain() {
        let validator = StreamingUxValidator::new()
            .with_max_latency(Duration::from_millis(150))
            .with_buffer_underrun_threshold(10)
            .with_max_dropped_frames(20)
            .with_min_fps(45.0)
            .with_ttfb_timeout(Duration::from_secs(5));

        assert_eq!(validator.max_latency, Duration::from_millis(150));
        assert_eq!(validator.buffer_underrun_threshold, 10);
        assert_eq!(validator.max_dropped_frames, 20);
        assert!((validator.min_fps - 45.0).abs() < f64::EPSILON);
        assert_eq!(validator.ttfb_timeout, Duration::from_secs(5));
    }

    #[test]
    fn test_streaming_validator_for_audio_preset() {
        let validator = StreamingUxValidator::for_audio();
        assert_eq!(validator.max_latency, Duration::from_millis(100));
        assert_eq!(validator.buffer_underrun_threshold, 3);
        assert_eq!(validator.ttfb_timeout, Duration::from_secs(2));
    }

    #[test]
    fn test_streaming_validator_for_video_preset() {
        let validator = StreamingUxValidator::for_video();
        assert_eq!(validator.max_latency, Duration::from_millis(500));
        assert!((validator.min_fps - 30.0).abs() < f64::EPSILON);
        assert_eq!(validator.max_dropped_frames, 5);
    }

    #[test]
    fn test_streaming_validator_average_fps_no_frames() {
        let validator = StreamingUxValidator::new();
        assert!((validator.average_fps() - 0.0).abs() < f64::EPSILON);
    }

    #[test]
    fn test_streaming_validator_average_fps_one_frame() {
        let mut validator = StreamingUxValidator::new();
        validator.record_metric(StreamingMetric::FrameRendered { timestamp: 1000 });
        assert!((validator.average_fps() - 0.0).abs() < f64::EPSILON);
    }

    #[test]
    fn test_streaming_validator_average_fps_same_timestamp() {
        let mut validator = StreamingUxValidator::new();
        validator.record_metric(StreamingMetric::FrameRendered { timestamp: 1000 });
        validator.record_metric(StreamingMetric::FrameRendered { timestamp: 1000 });
        validator.record_metric(StreamingMetric::FrameRendered { timestamp: 1000 });
        // Zero duration should return 0 fps
        assert!((validator.average_fps() - 0.0).abs() < f64::EPSILON);
    }

    #[test]
    fn test_streaming_validator_max_recorded_latency_none() {
        let validator = StreamingUxValidator::new();
        let result = validator.validate();
        assert!(result.is_ok());
        let res = result.unwrap();
        assert_eq!(res.max_latency_recorded, Duration::ZERO);
    }

    #[test]
    fn test_streaming_validator_validate_no_ttfb() {
        let mut validator = StreamingUxValidator::new();
        validator.start();
        // No first byte received, but should still validate
        let result = validator.validate();
        assert!(result.is_ok());
    }

    #[test]
    fn test_streaming_validator_complete_and_validate() {
        let mut validator = StreamingUxValidator::new();
        validator.complete();
        assert_eq!(validator.state(), StreamingState::Completed);
        let result = validator.validate();
        assert!(result.is_ok());
    }

    #[test]
    fn test_streaming_validator_error_and_validate() {
        let mut validator = StreamingUxValidator::new();
        validator.error();
        assert_eq!(validator.state(), StreamingState::Error);
        let result = validator.validate();
        assert!(result.is_err());
    }

    #[test]
    fn test_streaming_validator_state_history_empty() {
        let validator = StreamingUxValidator::new();
        assert!(validator.state_history().is_empty());
    }

    #[test]
    fn test_streaming_validator_state_history_with_transitions() {
        let mut validator = StreamingUxValidator::new();
        validator.start();
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });
        validator.complete();

        let history = validator.state_history();
        assert!(history.len() >= 2);
    }

    #[test]
    fn test_streaming_validator_reset_full() {
        let mut validator = StreamingUxValidator::new();
        validator.start();
        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(50)));
        validator.record_metric(StreamingMetric::BufferUnderrun);
        validator.record_metric(StreamingMetric::FrameDropped);
        validator.record_metric(StreamingMetric::FirstByteReceived);
        validator.record_metric(StreamingMetric::FrameRendered { timestamp: 100 });

        validator.reset();

        assert_eq!(validator.state(), StreamingState::Idle);
        assert_eq!(validator.buffer_underruns(), 0);
        assert_eq!(validator.dropped_frames(), 0);
        assert!(validator.state_history().is_empty());
    }

    #[test]
    fn test_streaming_validator_validate_all_with_error_state() {
        let mut validator = StreamingUxValidator::new();
        validator.error();
        let errors = validator.validate_all();
        assert!(errors
            .iter()
            .any(|e| matches!(e, StreamingValidationError::EndedInError)));
    }

    #[test]
    fn test_streaming_validation_result_fields_all() {
        let result = StreamingValidationResult {
            buffer_underruns: 1,
            dropped_frames: 2,
            average_fps: 30.0,
            max_latency_recorded: Duration::from_millis(50),
            total_frames: 100,
        };
        assert_eq!(result.buffer_underruns, 1);
        assert_eq!(result.dropped_frames, 2);
        assert!((result.average_fps - 30.0).abs() < f64::EPSILON);
        assert_eq!(result.max_latency_recorded, Duration::from_millis(50));
        assert_eq!(result.total_frames, 100);
    }

    #[test]
    fn test_state_transition_struct_fields_all() {
        let transition = StateTransition {
            from: "StateA".to_string(),
            to: "StateB".to_string(),
            timestamp_ms: 100.0,
            duration_ms: 50.0,
        };
        assert_eq!(&transition.from, "StateA");
        assert_eq!(&transition.to, "StateB");
        assert!((transition.timestamp_ms - 100.0).abs() < f64::EPSILON);
        assert!((transition.duration_ms - 50.0).abs() < f64::EPSILON);
    }

    #[test]
    fn test_partial_result_struct_fields() {
        let partial = PartialResult {
            timestamp_ms: 200.0,
            text: "partial text".to_string(),
            is_final: false,
        };
        assert!((partial.timestamp_ms - 200.0).abs() < f64::EPSILON);
        assert_eq!(&partial.text, "partial text");
        assert!(!partial.is_final);

        let final_result = PartialResult {
            timestamp_ms: 300.0,
            text: "final text".to_string(),
            is_final: true,
        };
        assert!(final_result.is_final);
    }

    #[test]
    fn test_vu_meter_sample_struct_fields() {
        let sample = VuMeterSample {
            timestamp_ms: 150.0,
            level: 0.65,
        };
        assert!((sample.timestamp_ms - 150.0).abs() < f64::EPSILON);
        assert!((sample.level - 0.65).abs() < f32::EPSILON);
    }

    #[test]
    fn test_streaming_metric_record_struct() {
        let now = Instant::now();
        let record = StreamingMetricRecord {
            metric: StreamingMetric::FrameDropped,
            timestamp: now,
        };
        assert!(matches!(record.metric, StreamingMetric::FrameDropped));
        assert_eq!(record.timestamp, now);
    }

    #[test]
    fn test_streaming_metric_latency_variant() {
        let metric = StreamingMetric::Latency(Duration::from_millis(123));
        if let StreamingMetric::Latency(d) = metric {
            assert_eq!(d, Duration::from_millis(123));
        } else {
            panic!("Expected Latency variant");
        }
    }

    #[test]
    fn test_streaming_metric_frame_rendered_variant() {
        let metric = StreamingMetric::FrameRendered { timestamp: 999 };
        if let StreamingMetric::FrameRendered { timestamp } = metric {
            assert_eq!(timestamp, 999);
        } else {
            panic!("Expected FrameRendered variant");
        }
    }

    #[test]
    fn test_streaming_metric_buffer_level_variant() {
        let metric = StreamingMetric::BufferLevel(0.42);
        if let StreamingMetric::BufferLevel(level) = metric {
            assert!((level - 0.42).abs() < f32::EPSILON);
        } else {
            panic!("Expected BufferLevel variant");
        }
    }

    #[test]
    fn test_streaming_metric_audio_chunk_variant() {
        let metric = StreamingMetric::AudioChunk {
            samples: 2048,
            sample_rate: 44100,
        };
        if let StreamingMetric::AudioChunk {
            samples,
            sample_rate,
        } = metric
        {
            assert_eq!(samples, 2048);
            assert_eq!(sample_rate, 44100);
        } else {
            panic!("Expected AudioChunk variant");
        }
    }

    #[test]
    fn test_compression_algorithm_eq() {
        assert_eq!(CompressionAlgorithm::Lz4, CompressionAlgorithm::Lz4);
        assert_eq!(CompressionAlgorithm::Zstd, CompressionAlgorithm::Zstd);
        assert_eq!(CompressionAlgorithm::Png, CompressionAlgorithm::Png);
        assert_eq!(CompressionAlgorithm::Rle, CompressionAlgorithm::Rle);
    }

    #[test]
    fn test_streaming_state_eq() {
        assert_eq!(StreamingState::Idle, StreamingState::Idle);
        assert_eq!(StreamingState::Buffering, StreamingState::Buffering);
        assert_eq!(StreamingState::Streaming, StreamingState::Streaming);
        assert_eq!(StreamingState::Stalled, StreamingState::Stalled);
        assert_eq!(StreamingState::Error, StreamingState::Error);
        assert_eq!(StreamingState::Completed, StreamingState::Completed);
    }

    #[test]
    fn test_streaming_state_ne() {
        assert_ne!(StreamingState::Idle, StreamingState::Buffering);
        assert_ne!(StreamingState::Streaming, StreamingState::Stalled);
        assert_ne!(StreamingState::Error, StreamingState::Completed);
    }

    #[test]
    fn test_vu_meter_error_debug() {
        let errors = vec![
            VuMeterError::NegativeLevel(-1.0),
            VuMeterError::Clipping(2.0),
            VuMeterError::Stale {
                last_update_ms: 100,
                current_ms: 200,
            },
            VuMeterError::SlowUpdateRate {
                measured_hz: 10.0,
                expected_hz: 30.0,
            },
            VuMeterError::NotAnimating {
                sample_count: 5,
                value: 0.5,
            },
        ];

        for err in errors {
            let debug = format!("{:?}", err);
            assert!(!debug.is_empty());
        }
    }

    #[test]
    fn test_streaming_validation_error_debug() {
        let errors: Vec<StreamingValidationError> = vec![
            StreamingValidationError::LatencyExceeded {
                measured: Duration::from_millis(100),
                max: Duration::from_millis(50),
            },
            StreamingValidationError::BufferUnderrunThreshold {
                count: 5,
                threshold: 3,
            },
            StreamingValidationError::DroppedFrameThreshold { count: 10, max: 5 },
            StreamingValidationError::FpsBelowMinimum {
                measured: 15.0,
                min: 30.0,
            },
            StreamingValidationError::TtfbExceeded {
                measured: Duration::from_secs(5),
                max: Duration::from_secs(2),
            },
            StreamingValidationError::InvalidStateTransition {
                from: StreamingState::Idle,
                to: StreamingState::Error,
            },
            StreamingValidationError::EndedInError,
        ];

        for err in errors {
            let debug = format!("{:?}", err);
            assert!(!debug.is_empty());
        }
    }

    #[test]
    fn test_screenshot_content_classify_boundary_uniform() {
        // Exactly 95% same value should still be Uniform (> 0.95)
        let mut pixels = vec![100u8; 96];
        pixels.extend(vec![200u8; 4]);
        let content = ScreenshotContent::classify(&pixels);
        assert!(matches!(
            content,
            ScreenshotContent::Uniform { fill_value: 100 }
        ));
    }

    #[test]
    fn test_screenshot_content_classify_just_under_uniform() {
        // 94% same value should NOT be uniform
        let mut pixels = vec![100u8; 94];
        pixels.extend(vec![200u8; 6]);
        let content = ScreenshotContent::classify(&pixels);
        // Should not be Uniform
        assert!(!matches!(content, ScreenshotContent::Uniform { .. }));
    }

    #[test]
    fn test_test_execution_stats_reset_clears_timing() {
        let mut stats = TestExecutionStats::new();
        stats.start();
        stats.record_state_capture(1000, 100);
        stats.stop();

        // Verify we have throughput
        assert!(stats.compress_throughput() > 0.0 || stats.bytes_raw > 0);

        stats.reset();

        // After reset, throughput should be 0 (no timing data)
        assert!((stats.compress_throughput() - 0.0).abs() < f64::EPSILON);
        assert_eq!(stats.states_captured, 0);
        assert_eq!(stats.bytes_raw, 0);
        assert_eq!(stats.bytes_compressed, 0);
        assert_eq!(stats.same_fill_pages, 0);
    }

    #[test]
    fn test_frame_times_cap_at_120() {
        let mut validator = StreamingUxValidator::new();

        // Add 200 frames
        for i in 0..200 {
            validator.record_metric(StreamingMetric::FrameRendered { timestamp: i * 16 });
        }

        // Frame times should be capped (checked via FPS calculation working)
        let fps = validator.average_fps();
        assert!(fps > 0.0);
    }

    #[test]
    fn test_latency_metric_triggers_buffering_to_streaming() {
        let mut validator =
            StreamingUxValidator::new().with_max_latency(Duration::from_millis(200));
        validator.start();
        assert_eq!(validator.state(), StreamingState::Buffering);

        // Good latency should transition to Streaming
        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(50)));
        assert_eq!(validator.state(), StreamingState::Streaming);
    }

    #[test]
    fn test_latency_metric_high_latency_no_transition() {
        let mut validator = StreamingUxValidator::new().with_max_latency(Duration::from_millis(50));
        validator.start();
        assert_eq!(validator.state(), StreamingState::Buffering);

        // High latency should NOT transition to Streaming
        validator.record_metric(StreamingMetric::Latency(Duration::from_millis(100)));
        assert_eq!(validator.state(), StreamingState::Buffering);
    }

    #[test]
    fn test_buffer_level_stall_only_when_streaming() {
        let mut validator = StreamingUxValidator::new();
        // In Idle state
        validator.record_metric(StreamingMetric::BufferLevel(0.01));
        assert_eq!(validator.state(), StreamingState::Idle);

        // In Buffering state
        validator.start();
        validator.record_metric(StreamingMetric::BufferLevel(0.01));
        assert_eq!(validator.state(), StreamingState::Buffering);
    }

    #[test]
    fn test_buffer_level_recovery_only_when_stalled() {
        let mut validator = StreamingUxValidator::new();
        validator.start();
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });
        assert_eq!(validator.state(), StreamingState::Streaming);

        // High buffer level should NOT change state when already Streaming
        validator.record_metric(StreamingMetric::BufferLevel(0.9));
        assert_eq!(validator.state(), StreamingState::Streaming);
    }

    #[test]
    fn test_frame_rendered_recovery_from_stalled() {
        let mut validator = StreamingUxValidator::new();
        validator.start();
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });
        validator.record_metric(StreamingMetric::BufferLevel(0.01)); // Stall

        assert_eq!(validator.state(), StreamingState::Stalled);

        // Frame rendered should recover
        validator.record_metric(StreamingMetric::FrameRendered { timestamp: 100 });
        assert_eq!(validator.state(), StreamingState::Streaming);
    }

    #[test]
    fn test_audio_chunk_only_transitions_from_buffering() {
        let mut validator = StreamingUxValidator::new();

        // In Idle - should not transition
        validator.record_metric(StreamingMetric::AudioChunk {
            samples: 1024,
            sample_rate: 16000,
        });
        assert_eq!(validator.state(), StreamingState::Idle);
    }

    #[test]
    fn test_first_byte_received_only_transitions_from_idle() {
        let mut validator = StreamingUxValidator::new();
        validator.start(); // Now in Buffering

        // FirstByte when already buffering should not re-transition
        validator.record_metric(StreamingMetric::FirstByteReceived);
        assert_eq!(validator.state(), StreamingState::Buffering);
    }

    #[test]
    fn test_buffer_underrun_only_stalls_when_streaming() {
        let mut validator = StreamingUxValidator::new();

        // In Idle - underrun should not change state
        validator.record_metric(StreamingMetric::BufferUnderrun);
        assert_eq!(validator.state(), StreamingState::Idle);

        // In Buffering - underrun should not change state
        validator.start();
        validator.record_metric(StreamingMetric::BufferUnderrun);
        assert_eq!(validator.state(), StreamingState::Buffering);
    }

    #[test]
    fn test_validate_all_fps_error() {
        let mut validator = StreamingUxValidator::new().with_min_fps(60.0);

        // Add slow frames
        for i in 0..10 {
            validator.record_metric(StreamingMetric::FrameRendered {
                timestamp: i * 100, // 10 fps
            });
        }

        let errors = validator.validate_all();
        assert!(errors
            .iter()
            .any(|e| matches!(e, StreamingValidationError::FpsBelowMinimum { .. })));
    }

    #[test]
    fn test_validate_all_buffer_underrun_error() {
        let mut validator = StreamingUxValidator::new().with_buffer_underrun_threshold(1);

        validator.record_metric(StreamingMetric::BufferUnderrun);
        validator.record_metric(StreamingMetric::BufferUnderrun);

        let errors = validator.validate_all();
        assert!(errors
            .iter()
            .any(|e| matches!(e, StreamingValidationError::BufferUnderrunThreshold { .. })));
    }

    #[test]
    fn test_validate_all_dropped_frames_error() {
        let mut validator = StreamingUxValidator::new().with_max_dropped_frames(1);

        validator.record_metric(StreamingMetric::FrameDropped);
        validator.record_metric(StreamingMetric::FrameDropped);

        let errors = validator.validate_all();
        assert!(errors
            .iter()
            .any(|e| matches!(e, StreamingValidationError::DroppedFrameThreshold { .. })));
    }

    #[test]
    fn test_streaming_state_copy_clone() {
        let state = StreamingState::Streaming;
        let copied = state;
        let cloned = state;
        assert_eq!(copied, cloned);
        assert_eq!(state, StreamingState::Streaming);
    }

    #[test]
    fn test_compression_algorithm_copy_clone() {
        let algo = CompressionAlgorithm::Zstd;
        let copied = algo;
        let cloned = algo;
        assert_eq!(copied, cloned);
        assert_eq!(algo, CompressionAlgorithm::Zstd);
    }
}