I am new to ZIO and ZIO Test and I'd like to test a scheduling service I wrote under ZIO v1.0.0RC17:
The service(s):
import zio.{RIO, Schedule}
import zio.clock.Clock
import zio.duration._
trait ModuleA {
def moduleA: ModuleA.Service
}
object ModuleA {
trait Service {
def schedule(arg: Int): RIO[Clock, Unit]
}
}
trait ModuleALive extends ModuleA {
def moduleB: ModuleB.Service
override def moduleA: ModuleA.Service = new ModuleA.Service {
override def schedule(arg: Int): RIO[Clock, Unit] = {
moduleB.run(arg).repeat(Schedule.spaced(1 day)).map(_ => ())
}
}
}
trait ModuleB {
def moduleB: ModuleB.Service
}
object ModuleB {
trait Service {
def run(arg: Int): RIO[Clock, Unit]
}
}
The service of ModuleA should basically run the Service method of ModuleB once a day with the argument fed into ModuleA.Service.run.
The test I'd like to write:
import java.util.concurrent.atomic.AtomicInteger
import zio.clock.Clock
import zio.duration._
import zio.test.environment.TestClock
import zio.test.{DefaultRunnableSpec, assertCompletes, suite, testM}
import zio.{RIO, Task, ZIO}
object ExampleSpec extends DefaultRunnableSpec(ExampleSuite.suite1)
object ExampleSuite {
val counter: AtomicInteger = new AtomicInteger(0)
trait ModuleBTest extends ModuleB {
override def moduleB: ModuleB.Service = new ModuleB.Service {
override def run(arg: Int): RIO[Clock, Unit] = ZIO.effectTotal(counter.incrementAndGet())
}
}
object ModuleATest extends ModuleALive with ModuleBTest
def verifyExpectedInvocationCount(expectedInvocationCount: Int): Task[Unit] = {
val actualInvocations = counter.get()
if (counter.get() == expectedInvocationCount)
ZIO.succeed(())
else
throw new Exception(s"expected invocation count: $expectedInvocationCount but was $actualInvocations")
}
val suite1 = suite("a")(
testM("a should correctly schedule b") {
for {
_ <- ModuleATest.moduleA.schedule(42).fork
_ <- TestClock.adjust(12 hours)
_ <- verifyExpectedInvocationCount(1)
_ <- TestClock.adjust(12 hours)
_ <- verifyExpectedInvocationCount(2)
} yield assertCompletes
}
)
}
I simplified the test using a counter, in reality I'd like to use mockito to verify the invocation count as well as the correct argument. However, this test does not work. In my understanding this is because of a race condition introduced by a timing overhead as described in https://zio.dev/docs/howto/howto_test_effects#testing-clock.
Now, there are examples of how to tackle this problem by using a Promise. I tried that by replacing the counter with a promise like so:
import java.util.concurrent.atomic.AtomicInteger
import zio.test.{DefaultRunnableSpec, assertCompletes, suite, testM}
import zio.{Promise, Task, UIO, ZIO}
object ExampleSpec extends DefaultRunnableSpec(ExampleSuite.suite1)
object ExampleSuite {
val counter: AtomicInteger = new AtomicInteger(0)
var promise: UIO[Promise[Unit, Int]] = Promise.make[Unit, Int]
trait ModuleBTest extends ModuleB {
override def moduleB: ModuleB.Service = new ModuleB.Service {
override def run(arg: Int) = promise.map(_.succeed(counter.incrementAndGet))
}
}
object ModuleATest extends ModuleALive with ModuleBTest
def verifyExpectedInvocationCount(expectedInvocationCount: Int, actualInvocations: Int): Task[Unit] = {
if (actualInvocations == expectedInvocationCount)
ZIO.succeed(())
else
throw new Exception(s"expected invocation count: $expectedInvocationCount but was $actualInvocations")
}
val suite1 = suite("a")(
testM("a should correctly schedule b") {
for {
_ <- ModuleATest.moduleA.schedule(42).fork
p <- promise
actualInvocationCount <- p.await
_ <- verifyExpectedInvocationCount(expectedInvocationCount = 1, actualInvocationCount)
} yield assertCompletes
}
)
}
Using this, the test won't terminate. However, I am pretty sure I am using the promise wrongly.
How would one approach this test scenario correctly?
In your example the type of promise is UIO[Promise[Unit, Int]] so you are creating a new promise each time. As a result, the promise your effect is completing is different than the one your test is waiting on, resulting in nontermination.
To test this, you can do something like this:
import zio.clock.Clock
import zio.duration._
import zio.test.environment.TestClock
import zio.test.{ assertCompletes, suite, testM, DefaultRunnableSpec }
import zio._
object ExampleSpec extends DefaultRunnableSpec {
trait ModuleA {
def moduleA: ModuleA.Service
}
object ModuleA {
trait Service {
def schedule(arg: Int): RIO[Clock, Unit]
}
}
trait ModuleALive extends ModuleA {
def moduleB: ModuleB.Service
override def moduleA: ModuleA.Service = new ModuleA.Service {
override def schedule(arg: Int): RIO[Clock, Unit] =
moduleB.run(arg).repeat(Schedule.spaced(1.day)).map(_ => ())
}
}
trait ModuleB {
def moduleB: ModuleB.Service
}
object ModuleB {
trait Service {
def run(arg: Int): RIO[Clock, Unit]
}
}
trait ModuleBTest extends ModuleB {
val counter: Ref[Int]
val invocations: Queue[Int]
override def moduleB: ModuleB.Service = new ModuleB.Service {
override def run(arg: Int): UIO[Unit] =
counter.updateAndGet(_ + 1).flatMap(invocations.offer).unit
}
}
object ModuleATest {
def apply(ref: Ref[Int], queue: Queue[Int]): ModuleALive with ModuleBTest =
new ModuleALive with ModuleBTest {
val counter = ref
val invocations = queue
}
}
def verifyExpectedInvocationCount(invocations: Queue[Int], expected: Int): Task[Unit] =
invocations.take.flatMap { actual =>
if (actual == expected)
ZIO.succeed(())
else
ZIO.fail(new Exception(s"expected invocation count: $expected but was $actual"))
}
def spec = suite("a")(
testM("a should correctly schedule b") {
for {
counter <- Ref.make(0)
invocations <- Queue.unbounded[Int]
moduleATest = ModuleATest(counter, invocations)
_ <- moduleATest.moduleA.schedule(42).fork
_ <- TestClock.adjust(12.hours)
_ <- verifyExpectedInvocationCount(invocations, 1)
_ <- TestClock.adjust(12.hours)
_ <- verifyExpectedInvocationCount(invocations, 2)
} yield assertCompletes
}
)
}
Since we want to wait for multiple effects to complete I use a Queue to coordinate them. A couple of other things to note:
verifyExpectedInvocationsCount method with the use of the assertions in ZIO Test to get better error reporting.TestAspect#nonTermination.