trait TestClock extends Restorable
TestClock
makes it easy to deterministically and efficiently test
effects involving the passage of time.
Instead of waiting for actual time to pass, sleep
and methods
implemented in terms of it schedule effects to take place at a given clock
time. Users can adjust the clock time using the adjust
and setTime
methods, and all effects scheduled to take place on or before that time
will automatically be run in order.
For example, here is how we can test ZIO#timeout
using TestClock
:
import zio.ZIO import zio.test.environment.TestClock for { fiber <- ZIO.sleep(5.minutes).timeout(1.minute).fork _ <- TestClock.adjust(1.minute) result <- fiber.join } yield result == None
Note how we forked the fiber that sleep
was invoked on. Calls to sleep
and methods derived from it will semantically block until the time is set
to on or after the time they are scheduled to run. If we didn't fork the
fiber on which we called sleep we would never get to set the time on the
line below. Thus, a useful pattern when using TestClock
is to fork the
effect being tested, then adjust the clock time, and finally verify that
the expected effects have been performed.
For example, here is how we can test an effect that recurs with a fixed delay:
import zio.Queue import zio.test.environment.TestClock for { q <- Queue.unbounded[Unit] _ <- q.offer(()).delay(60.minutes).forever.fork a <- q.poll.map(_.isEmpty) _ <- TestClock.adjust(60.minutes) b <- q.take.as(true) c <- q.poll.map(_.isEmpty) _ <- TestClock.adjust(60.minutes) d <- q.take.as(true) e <- q.poll.map(_.isEmpty) } yield a && b && c && d && e
Here we verify that no effect is performed before the recurrence period, that an effect is performed after the recurrence period, and that the effect is performed exactly once. The key thing to note here is that after each recurrence the next recurrence is scheduled to occur at the appropriate time in the future, so when we adjust the clock by 60 minutes exactly one value is placed in the queue, and when we adjust the clock by another 60 minutes exactly one more value is placed in the queue.
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- abstract def adjust(duration: zio.Duration)(implicit trace: ZTraceElement): UIO[Unit]
- abstract def save(implicit trace: ZTraceElement): UIO[UIO[Unit]]
- Definition Classes
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- abstract def setDateTime(dateTime: OffsetDateTime)(implicit trace: ZTraceElement): UIO[Unit]
- abstract def setTime(duration: zio.Duration)(implicit trace: ZTraceElement): UIO[Unit]
- abstract def setTimeZone(zone: ZoneId)(implicit trace: ZTraceElement): UIO[Unit]
- abstract def sleeps(implicit trace: ZTraceElement): UIO[List[zio.Duration]]
- abstract def timeZone(implicit trace: ZTraceElement): UIO[ZoneId]
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