Data
represents the state of the TestClock
, including the clock time
and time zone.
Sleep
represents the state of a scheduled effect, including the time
the effect is scheduled to run, a promise that can be completed to resume
execution of the effect, and the fiber executing the effect.
WarningData
describes the state of the warning message that is
displayed if a test is using time by is not advancing the TestClock
.
WarningData
describes the state of the warning message that is
displayed if a test is using time by is not advancing the TestClock
.
The possible states are Start
if a test has not used time, Pending
if
a test has used time but has not adjusted the TestClock
, and Done
if
a test has adjusted the TestClock
or the warning message has already
been displayed.
Accesses a TestClock
instance in the environment and increments the
time by the specified duration, running any actions scheduled for on or
before the new time in order.
Constructs a new Test
object that implements the TestClock
interface.
Constructs a new Test
object that implements the TestClock
interface.
This can be useful for mixing in with implementations of other
interfaces.
Accesses a TestClock
instance in the environment and saves the clock
state in an effect which, when run, will restore the TestClock
to the
saved state.
Accesses a TestClock
instance in the environment and sets the clock
time to the specified OffsetDateTime
, running any actions scheduled for
on or before the new time in order.
Accesses a TestClock
instance in the environment and sets the clock
time to the specified time in terms of duration since the epoch, running
any actions scheduled for on or before the new time in order.
Accesses a TestClock
instance in the environment, setting the time zone
to the specified time zone.
Accesses a TestClock
instance in the environment, setting the time zone
to the specified time zone. The clock time in terms of nanoseconds since
the epoch will not be altered and no scheduled actions will be run as a
result of this effect.
Accesses a TestClock
instance in the environment and returns a list of
times that effects are scheduled to run.
Accesses a TestClock
instance in the environment and returns the
current time zone.
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 theadjust
andsetTime
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
usingTestClock:
Note how we forked the fiber that
sleep
was invoked on. Calls tosleep
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 usingTestClock
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:
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.