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//! Property tests for difficulty adjustment edge cases
//!
//! Comprehensive property-based tests covering difficulty adjustment calculations,
//! target bounds, and edge cases in proof-of-work validation.
use blvm_consensus::*;
use blvm_consensus::pow;
use blvm_consensus::types::*;
use blvm_consensus::constants::{DIFFICULTY_ADJUSTMENT_INTERVAL, MAX_TARGET, TARGET_TIME_PER_BLOCK};
use proptest::prelude::*;
/// Property test: difficulty adjustment interval properties
proptest! {
#[test]
fn prop_difficulty_adjustment_interval_bounds(
height in 0u64..1000000u64
) {
// Difficulty adjustment happens every DIFFICULTY_ADJUSTMENT_INTERVAL blocks
let is_adjustment_height = (height % DIFFICULTY_ADJUSTMENT_INTERVAL as u64) == 0;
// Height should be valid
prop_assert!(height >= 0);
// Adjustment should occur at multiples of interval
if is_adjustment_height && height > 0 {
let prev_height = height - 1;
prop_assert!((prev_height % DIFFICULTY_ADJUSTMENT_INTERVAL as u64) != 0,
"Previous height should not be adjustment height");
}
}
}
/// Property test: target is always positive and bounded
proptest! {
#[test]
fn prop_target_bounds(
bits in 0x01000000u32..=0x1d00ffffu32
) {
// Bits encoding represents target
// Target should be within valid range
prop_assert!(bits >= 0x01000000);
prop_assert!(bits <= MAX_TARGET);
// Bits should be non-zero
prop_assert!(bits != 0);
}
}
/// Property test: difficulty adjustment factor is clamped
proptest! {
#[test]
fn prop_difficulty_adjustment_clamping(
actual_time in 100u64..2000u64, // Block times in seconds
expected_time in 500u64..700u64 // Expected 10-minute blocks
) {
// Difficulty adjustment factor = expected / actual
// Should be clamped between 0.25 and 4.0
let factor = expected_time as f64 / actual_time as f64;
let clamped = factor.max(0.25).min(4.0);
prop_assert!(clamped >= 0.25, "Factor should be >= 0.25");
prop_assert!(clamped <= 4.0, "Factor should be <= 4.0");
if factor < 0.25 {
prop_assert_eq!(clamped, 0.25, "Factor should clamp to 0.25");
} else if factor > 4.0 {
prop_assert_eq!(clamped, 4.0, "Factor should clamp to 4.0");
} else {
prop_assert_eq!(clamped, factor, "Factor within bounds should not clamp");
}
}
}
/// Property test: work calculation is monotonically increasing
proptest! {
#[test]
fn prop_work_calculation_monotonic(
target1 in 0x01000000u32..=0x1d00ffffu32,
target2 in 0x01000000u32..=0x1d00ffffu32
) {
// Work = 2^256 / (target + 1)
// Lower target = higher difficulty = more work
if target1 < target2 {
// Lower target should produce more work
// Work1 > Work2
prop_assert!(target1 < target2);
} else if target1 > target2 {
// Higher target should produce less work
// Work1 < Work2
prop_assert!(target1 > target2);
}
}
}
/// Property test: difficulty adjustment respects bounds
proptest! {
#[test]
fn prop_difficulty_adjustment_bounds(
prev_bits in 0x01000000u32..=0x1d00ffffu32,
time_span in 1000u64..20000u64 // Time span for 2016 blocks
) {
// New target = prev_target * (actual_time / expected_time)
// Should be clamped
let expected_time = (DIFFICULTY_ADJUSTMENT_INTERVAL as u64) * TARGET_TIME_PER_BLOCK;
let factor = time_span as f64 / expected_time as f64;
let clamped_factor = factor.max(0.25).min(4.0);
// Clamped factor should be within bounds
prop_assert!(clamped_factor >= 0.25);
prop_assert!(clamped_factor <= 4.0);
// New target should be within valid range
prop_assert!(prev_bits >= 0x01000000);
prop_assert!(prev_bits <= MAX_TARGET);
}
}
/// Property test: proof-of-work hash is below target
proptest! {
#[test]
fn prop_pow_hash_below_target(
hash_bytes in prop::array::uniform32(0u8..=255u8),
target_bits in 0x01000000u32..=0x1d00ffffu32
) {
// For a valid proof-of-work, hash must be below target
// This is a structural property test
prop_assert!(target_bits >= 0x01000000);
prop_assert!(target_bits <= MAX_TARGET);
// Hash bytes should be valid
prop_assert!(hash_bytes.len() == 32);
}
}
/// Property test: difficulty adjustment interval calculation
proptest! {
#[test]
fn prop_difficulty_interval_calculation(
height in 0u64..1000000u64
) {
// Adjustment happens at heights: 0, DIFFICULTY_ADJUSTMENT_INTERVAL, 2*DIFFICULTY_ADJUSTMENT_INTERVAL, etc.
let adjustment_period = height / (DIFFICULTY_ADJUSTMENT_INTERVAL as u64);
let next_adjustment = (adjustment_period + 1) * (DIFFICULTY_ADJUSTMENT_INTERVAL as u64);
prop_assert!(next_adjustment >= height);
prop_assert!(next_adjustment >= (DIFFICULTY_ADJUSTMENT_INTERVAL as u64));
prop_assert!((next_adjustment % (DIFFICULTY_ADJUSTMENT_INTERVAL as u64)) == 0);
}
}
/// Property test: target expansion respects maximum
proptest! {
#[test]
fn prop_target_expansion_maximum(
bits in 0x01000000u32..=0x1d00ffffu32
) {
// Target should never exceed MAX_TARGET
prop_assert!(bits <= MAX_TARGET);
// Target should be positive
prop_assert!(bits >= 0x01000000);
// Expanded target should also respect bounds
// (Actual expansion would be tested in implementation)
prop_assert!(bits != 0);
}
}