Struct MockTimeSource 

pub struct MockTimeSource;

Mock time source for deterministic testing.

MockTimeSource provides a controllable time source where elapsed time can be manually set and advanced. This enables deterministic testing of rate limiting behavior without depending on real system time.

Time Model

MockTimeSource maintains an elapsed Duration since an implicit starting point. Time starts at Duration::ZERO and can be advanced or set to specific values. Time is always monotonic - attempting to set time backward will be ignored.

Thread Safety

MockTimeSource uses thread-local storage, so each thread has its own independent mock time. This is perfect for testing scenarios where you want isolated time control per test.

Examples

Basic Usage

use rate_guard::time_source::{TimeSource, MockTimeSource};
use std::time::Duration;

let time_source = MockTimeSource::new();

// Check initial state
assert_eq!(time_source.now(), Duration::ZERO);

// Advance time
time_source.advance(Duration::from_millis(50));
assert_eq!(time_source.now(), Duration::from_millis(50));

// Advance more
time_source.advance(Duration::from_millis(30));
assert_eq!(time_source.now(), Duration::from_millis(80));

Absolute Time Setting

use rate_guard::time_source::{TimeSource, MockTimeSource};
use std::time::Duration;

let time_source = MockTimeSource::new();

// Jump to specific time
time_source.set_elapsed(Duration::from_secs(10));
assert_eq!(time_source.now(), Duration::from_secs(10));

// Reset to zero
time_source.reset();
assert_eq!(time_source.now(), Duration::ZERO);

Rate Limiter Integration

use rate_guard::time_source::{TimeSource, MockTimeSource};
use std::time::Duration;

let time_source = MockTimeSource::new();

// Simulate token bucket refill timing
let refill_interval = Duration::from_millis(100);
let initial_time = time_source.now();

// Advance past refill interval
time_source.advance(refill_interval);
let elapsed = time_source.now() - initial_time;
assert!(elapsed >= refill_interval);

Implementations

impl MockTimeSource

pub fn new() -> Self

Creates a new MockTimeSource.

The time source starts with elapsed time of Duration::ZERO. Each instance shares the same thread-local time state within the current thread.

Examples

use rate_guard::time_source::{TimeSource, MockTimeSource};
use std::time::Duration;

let time_source = MockTimeSource::new();
assert_eq!(time_source.now(), Duration::ZERO);

pub fn set_elapsed(&self, elapsed: Duration)

Sets the elapsed time to a specific value.

This method allows tests to jump to any point in time. The time must be greater than or equal to the current elapsed time to maintain monotonicity. Attempts to set time backward are ignored.

Arguments

• elapsed - The new elapsed time value

Examples

use rate_guard::time_source::{TimeSource, MockTimeSource};
use std::time::Duration;

let time_source = MockTimeSource::new();

time_source.set_elapsed(Duration::from_millis(1000));
assert_eq!(time_source.now(), Duration::from_millis(1000));

// Attempting to go backward is ignored
time_source.set_elapsed(Duration::from_millis(500));
assert_eq!(time_source.now(), Duration::from_millis(1000));

pub fn advance(&self, duration: Duration)

Advances the elapsed time by the specified duration.

This method adds the specified duration to the current elapsed time, simulating the passage of time in tests. The advancement is always forward, maintaining monotonicity.

Arguments

• duration - Duration to advance the time by

Examples

use rate_guard::time_source::{TimeSource, MockTimeSource};
use std::time::Duration;

let time_source = MockTimeSource::new();

time_source.advance(Duration::from_millis(50));
assert_eq!(time_source.now(), Duration::from_millis(50));

time_source.advance(Duration::from_millis(25));
assert_eq!(time_source.now(), Duration::from_millis(75));

pub fn reset(&self)

Resets the elapsed time to zero.

This is a convenience method equivalent to set_elapsed(Duration::ZERO). Useful for resetting time state between tests.

Examples

use rate_guard::time_source::{TimeSource, MockTimeSource};
use std::time::Duration;

let time_source = MockTimeSource::new();
time_source.advance(Duration::from_secs(5));
assert_eq!(time_source.now(), Duration::from_secs(5));

time_source.reset();
assert_eq!(time_source.now(), Duration::ZERO);

pub fn elapsed(&self) -> Duration

Returns the current elapsed time.

This is equivalent to calling the now() method from the TimeSource trait, but provided as a convenience method with a more descriptive name.

Examples

use rate_guard::time_source::MockTimeSource;
use std::time::Duration;

let time_source = MockTimeSource::new();
time_source.advance(Duration::from_millis(100));

assert_eq!(time_source.elapsed(), Duration::from_millis(100));
assert_eq!(time_source.elapsed(), time_source.now());

pub fn now(&self) -> Duration

Trait Implementations

impl Clone for MockTimeSource

fn clone(&self) -> MockTimeSource

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for MockTimeSource

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for MockTimeSource

fn default() -> Self

Creates a new MockTimeSource with default settings.

Equivalent to MockTimeSource::new().

impl TimeSource for MockTimeSource

fn now(&self) -> Duration

Returns the current elapsed time since the mock starting point.

This method returns the elapsed Duration that has been set or advanced through the mock time control methods.

Examples

use rate_guard::time_source::{TimeSource, MockTimeSource};
use std::time::Duration;

let time_source = MockTimeSource::new();
assert_eq!(time_source.now(), Duration::ZERO);

time_source.advance(Duration::from_millis(123));
assert_eq!(time_source.now(), Duration::from_millis(123));