Struct TestClock

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pub struct TestClock { /* private fields */ }

Available on crate feature test-clock and (crate features test-clock) only.

Expand description

Owns a clock that moves only when advanced, for tests.

Self::clock hands out handles that read and sleep on its time. Only the owner moves it, through methods that take &mut self, so each test clock has one driver.

Implementations§

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impl TestClock

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pub fn new() -> Self

Creates a stopped clock at the current real monotonic and wall times.

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pub fn clock(&self) -> Clock

Returns a handle that reads and sleeps on this clock.

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pub fn advance(&mut self, by: Duration)

Moves both times forward by by, waking the sleeps and deadline waits it reaches and firing its due timers.

Returns once the reached waits are woken and the due timers hold their messages, without waiting for any thread to act. Other waits keep waiting, since an advance never counts as a notification. A zero advance does nothing.

§Panics

Panics if either time would overflow, before changing either one.

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pub fn advance_to(&mut self, target: Instant)

Moves monotonic time to target and wall time by the same amount, waking the sleeps and deadline waits it reaches and firing its due timers.

Returns once the reached waits are woken and the due timers hold their messages, without waiting for any thread to act. Other waits keep waiting, since an advance never counts as a notification. Advancing to the current time does nothing.

§Panics

Panics if target is before now or wall time would overflow. Neither time changes after a panic.

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pub fn set_system_time(&mut self, time: SystemTime)

Sets wall time forwards or backwards without moving monotonic time.

This wakes no waits and fires no timers, since deadlines use monotonic time.

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pub fn wait_blocked(&self, count: usize)

Blocks until at least count threads are parked in this clock’s sleeps and condvar waits.

Threads blocked in crossbeam receives and selects do not count. A thread parked earlier counts too, so the count proves no progress on its own. Nothing bounds the wait, so run tests under a runner with a per-test timeout, since cargo test alone never stops a hung test.

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pub fn wait_timers(&self, count: usize)

Available on crate feature crossbeam only.

Blocks until at least count timers are armed on this clock and unfired.

A waiting receive’s timer counts, and so does a timer whose receiver was dropped. A timer armed earlier counts too, so the count proves no progress on its own. Nothing bounds the wait, so run tests under a runner with a per-test timeout, since cargo test alone never stops a hung test.

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pub fn next_deadline(&self) -> Option<Instant>

Returns the earliest deadline among this clock’s parked sleeps, deadline waits and unfired timers, or None when there is none.

A timed wait stays listed until it stops waiting, so one an advance reaches stays listed until its thread runs, and the result is then the current time. Await an advance’s effect before reading the next deadline. A timer leaves the list when it fires.