Add support for async fixtures (#430)

Co-authored-by: Daniel Esik <[email protected]>

build.sbt

@@ -1,6 +1,4 @@
-import com.typesafe.tools.mima.core.DirectMissingMethodProblem
-import com.typesafe.tools.mima.core.ProblemFilters
-import com.typesafe.tools.mima.core.MissingTypesProblem
+import com.typesafe.tools.mima.core._
 import sbtcrossproject.CrossPlugin.autoImport.crossProject
 import sbtcrossproject.CrossPlugin.autoImport.CrossType
 import scala.collection.mutable
@@ -85,6 +83,26 @@ lazy val mimaEnable: List[Def.Setting[_]] = List(
     ),
     ProblemFilters.exclude[DirectMissingMethodProblem](
       "munit.internal.junitinterface.JUnitComputer.this"
+    ),
+    // Known breaking changes for MUnit v1
+    ProblemFilters.exclude[IncompatibleMethTypeProblem](
+      "munit.FunSuite.munitTestTransform"
+    ),
+    ProblemFilters.exclude[MissingClassProblem]("munit.GenericAfterEach"),
+    ProblemFilters.exclude[MissingClassProblem]("munit.GenericBeforeEach"),
+    ProblemFilters.exclude[MissingClassProblem]("munit.GenericTest"),
+    ProblemFilters.exclude[DirectMissingMethodProblem](
+      "munit.MUnitRunner.createTestDescription"
+    ),
+    ProblemFilters.exclude[IncompatibleMethTypeProblem](
+      "munit.Suite.beforeEach"
+    ),
+    ProblemFilters.exclude[IncompatibleMethTypeProblem](
+      "munit.Suite.afterEach"
+    ),
+    ProblemFilters.exclude[MissingClassProblem]("munit.Suite$Fixture"),
+    ProblemFilters.exclude[IncompatibleMethTypeProblem](
+      "munit.TestTransforms#TestTransform.apply"
     )
   ),
   mimaPreviousArtifacts := {

docs/fixtures.md

@@ -57,12 +57,12 @@ to reusable or ad-hoc fixtures when necessary.
 ## Reusable test-local fixtures
 
 Reusable test-local fixtures are more powerful than functional test-local
-fixtures because they can declare custom logic that gets evaluted before each
+fixtures because they can declare custom logic that gets evaluated before each
 local test case and get torn down after each test case. These increased
 capabilities come at the price of ergonomics of the API.
 
-Override the `beforeEach()` and `afterEach()` methods in the `Fixture[T]` trait
-to configure a reusable test-local fixture.
+Override the `beforeEach()`, `afterEach()` and `munitFixtures` methods in the
+`Fixture[T]` trait to configure a reusable test-local fixture.
 
 ```scala mdoc:reset
 import java.nio.file._
@@ -179,6 +179,73 @@ class MySuite extends munit.FunSuite {
 }
 ```
 
+## Asynchronous fixtures with `FutureFixture`
+
+Extend `FutureFixture[T]` to return `Future[T]` values from the lifecycle
+methods `beforeAll`, `beforeEach`, `afterEach` and `afterAll`.
+
+```scala mdoc:reset
+import java.nio.file._
+import java.sql.Connection
+import java.sql.DriverManager
+import munit.FutureFixture
+import munit.FunSuite
+import scala.concurrent.Future
+import scala.concurrent.ExecutionContext.Implicits.global
+
+class AsyncFilesSuite extends FunSuite {
+
+  val file = new FutureFixture[Path]("files") {
+    var file: Path = null
+    def apply() = file
+    override def beforeEach(context: BeforeEach): Future[Unit] = Future {
+      file = Files.createTempFile("files", context.test.name)
+    }
+    override def afterEach(context: AfterEach): Future[Unit] = Future {
+      // Always gets called, even if test failed.
+      Files.deleteIfExists(file)
+    }
+  }
+
+  override def munitFixtures = List(file)
+
+  test("exists") {
+    // `file` is the temporary file that was created for this test case.
+    assert(Files.exists(file()))
+  }
+}
+```
+
+## Asynchronous fixtures with custom effect type
+
+First, create a new `EffectFixture[T]` class that extends `munit.AnyFixture[T]`
+and overrides all lifecycle methods to return values of type `Effect[Unit]`. For
+example:
+
+```scala mdoc:reset
+import munit.AfterEach
+import munit.BeforeEach
+
+// Hypothetical effect type called "Resource"
+sealed abstract class Resource[+T]
+object Resource {
+  def unit: Resource[Unit] = ???
+}
+
+abstract class ResourceFixture[T](name: String) extends munit.AnyFixture[T](name) {
+  // The main purpose of "ResourceFixture" is to help IDEs auto-complete
+  // the result type "Resource[Unit]" instead of "Any" when implementing the
+  // "ResourceFixture" class.
+  override def beforeAll(): Resource[Unit] = Resource.unit
+  override def beforeEach(context: BeforeEach): Resource[Unit] = Resource.unit
+  override def afterEach(context: AfterEach): Resource[Unit] = Resource.unit
+  override def afterAll(): Resource[Unit] = Resource.unit
+}
+```
+
+Next, extend `munitValueTransforms` to convert `Resource[T]` into `Future[T]`,
+see [declare async tests](tests.md#declare-async-test) for more details.
+
 ## Avoid stateful operations in the class constructor
 
 Test classes may sometimes get initialized even if no tests run so it's best to

docs/tests.md

@@ -86,8 +86,8 @@ test("buggy-task") {
 ```
 
 Since tasks are lazy, a test that returns `LazyFuture[T]` will always pass since
-you need to call `run()` to start the task execution. Override `munitValueTransforms`
-to make sure that `LazyFuture.run()` gets called.
+you need to call `run()` to start the task execution. Override
+`munitValueTransforms` to make sure that `LazyFuture.run()` gets called.
 
 ```scala mdoc
 import scala.concurrent.ExecutionContext.Implicits.global
@@ -118,9 +118,10 @@ parallel test suite execution in sbt, add the following setting to `build.sbt`.
 Test / parallelExecution := false
 ```
 
-In case you do not run your tests in parallel, you can also disable buffered logging, 
-which is on by default to prevent test results of multiple suites from appearing interleaved.
-Switching buffering off would give you immediate feedback on the console while a suite is running.
+In case you do not run your tests in parallel, you can also disable buffered
+logging, which is on by default to prevent test results of multiple suites from
+appearing interleaved. Switching buffering off would give you immediate feedback
+on the console while a suite is running.
 
 ```sh
 Test / testOptions += Tests.Argument(TestFrameworks.MUnit, "-b")
@@ -199,9 +200,9 @@ bug report but don't have a solution to fix the issue yet.
 
 ## Customize evaluation of tests with tags
 
-Override `munitTestTransforms()` to extend the default behavior for how test bodies are
-evaluated. For example, use this feature to implement a `Rerun(N)` modifier to
-evaluate the body multiple times.
+Override `munitTestTransforms()` to extend the default behavior for how test
+bodies are evaluated. For example, use this feature to implement a `Rerun(N)`
+modifier to evaluate the body multiple times.
 
 ```scala mdoc
 case class Rerun(count: Int) extends munit.Tag("Rerun")
@@ -228,9 +229,9 @@ class MyRerunSuite extends munit.FunSuite {
 }
 ```
 
-The `munitTestTransforms()` method is similar to `munitValueTransforms()` but is different in
-that you also have access information about the test in `TestOptions` such as
-tags.
+The `munitTestTransforms()` method is similar to `munitValueTransforms()` but is
+different in that you also have access information about the test in
+`TestOptions` such as tags.
 
 ## Customize test name based on a dynamic condition
 
@@ -316,46 +317,3 @@ abstract class BaseSuite extends munit.FunSuite {
 class MyFirstSuite extends BaseSuite { /* ... */ }
 class MySecondSuite extends BaseSuite { /* ... */ }
 ```
-
-## Roll our own testing library with `munit.Suite`
-
-The `munit.FunSuite` class comes with a lot of built-in functionality such as
-assertions, fixtures, `munitTimeout()` helpers and more. These features may not
-be necessary or even desirable when writing tests. You may sometimes prefer a
-smaller API.
-
-Extend the base class `munit.Suite` to implement a minimal test suite that
-includes no optional MUnit features. At its core, MUnit operates on a data
-structure `GenericTest[TestValue]` where the type parameter `TestValue`
-represents the return value of test bodies. This type parameter can be
-customized per-suite. In `munit.FunSuite`, the type parameter `TestValue` is
-defined as `Any` and `type Test = GenericTest[Any]`.
-
-Below is an example custom test suite with `type TestValue = Future[String]`.
-
-```scala
-class MyCustomSuite extends munit.Suite {
-  override type TestValue = Future[String]
-  override def munitTests() = List(
-    new Test(
-      "name",
-      // compile error if it's not a Future[String]
-      body = () => Future.successful("Hello world!"),
-      tags = Set.empty[Tag],
-      location = implicitly[Location]
-    )
-  )
-}
-```
-
-Some use-cases where you may want to define a custom `munit.Suite`:
-
-- implement APIs that mimic testing libraries to simplify the migration to MUnit
-- design stricter APIs that don't use `Any`
-- design purely functional APIs with no publicly facing side-effects
-
-In application code, it's desirable to use strong types avoid mutable state.
-However, it's not clear that those best practices yield the same cost/benefit
-ratio when writing test code. MUnit intentionally exposes types such `Any` and
-side-effecting methods like `test("name") { ... }` because they subjectively
-make the testing API nice-to-use.

munit-scalacheck/shared/src/main/scala/munit/ScalaCheckSuite.scala

@@ -41,7 +41,7 @@ trait ScalaCheckSuite extends FunSuite {
     new TestTransform(
       "ScalaCheck Prop",
       t => {
-        t.withBodyMap[TestValue](
+        t.withBodyMap(
           _.transformCompat {
             case Success(prop: Prop) => propToTry(prop, t)
             case r                   => r

munit/js/src/main/scala/munit/internal/PlatformCompat.scala

@@ -9,6 +9,7 @@ import sbt.testing.EventHandler
 import sbt.testing.Logger
 import scala.concurrent.Promise
 import scala.concurrent.duration.Duration
+import scala.concurrent.ExecutionContext
 
 object PlatformCompat {
   def executeAsync(
@@ -20,7 +21,12 @@ object PlatformCompat {
     task.execute(eventHandler, loggers, _ => p.success(()))
     p.future
   }
-  def waitAtMost[T](future: Future[T], duration: Duration): Future[T] = {
+
+  def waitAtMost[T](
+      future: Future[T],
+      duration: Duration,
+      ec: ExecutionContext
+  ): Future[T] = {
     future
   }
 

munit/jvm/src/main/scala/munit/internal/PlatformCompat.scala

@@ -4,11 +4,15 @@ import scala.concurrent.Future
 import sbt.testing.Task
 import sbt.testing.EventHandler
 import sbt.testing.Logger
-import scala.concurrent.Await
 import scala.concurrent.duration.Duration
-import scala.util.Try
+import java.util.concurrent.Executors
+import scala.concurrent.Promise
+import scala.concurrent.ExecutionContext
+import java.util.concurrent.TimeUnit
+import java.util.concurrent.TimeoutException
 
 object PlatformCompat {
+  private val sh = Executors.newSingleThreadScheduledExecutor()
   def executeAsync(
       task: Task,
       eventHandler: EventHandler,
@@ -17,8 +21,38 @@ object PlatformCompat {
     task.execute(eventHandler, loggers)
     Future.successful(())
   }
-  def waitAtMost[T](future: Future[T], duration: Duration): Future[T] = {
-    Future.fromTry(Try(Await.result(future, duration)))
+  @deprecated("use the overload with an explicit ExecutionContext", "1.0.0")
+  def waitAtMost[T](
+      future: Future[T],
+      duration: Duration
+  ): Future[T] = {
+    waitAtMost(future, duration, ExecutionContext.global)
+  }
+  def waitAtMost[T](
+      future: Future[T],
+      duration: Duration,
+      ec: ExecutionContext
+  ): Future[T] = {
+    if (future.value.isDefined) {
+      // Avoid heavy timeout overhead for non-async tests.
+      future
+    } else {
+      val onComplete = Promise[T]()
+      var onCancel: () => Unit = () => ()
+      future.onComplete { result =>
+        onComplete.tryComplete(result)
+      }(ec)
+      val timeout = sh.schedule[Unit](
+        () =>
+          onComplete.tryFailure(
+            new TimeoutException(s"test timed out after $duration")
+          ),
+        duration.toMillis,
+        TimeUnit.MILLISECONDS
+      )
+      onCancel = () => timeout.cancel(false)
+      onComplete.future
+    }
   }
 
   def isIgnoreSuite(cls: Class[_]): Boolean =

munit/native/src/main/scala/munit/internal/PlatformCompat.scala

@@ -8,6 +8,7 @@ import sbt.testing.Task
 import sbt.testing.EventHandler
 import sbt.testing.Logger
 import scala.concurrent.duration.Duration
+import scala.concurrent.ExecutionContext
 
 object PlatformCompat {
   def executeAsync(
@@ -18,7 +19,11 @@ object PlatformCompat {
     task.execute(eventHandler, loggers)
     Future.successful(())
   }
-  def waitAtMost[T](future: Future[T], duration: Duration): Future[T] = {
+  def waitAtMost[T](
+      future: Future[T],
+      duration: Duration,
+      ec: ExecutionContext
+  ): Future[T] = {
     future
   }
 

munit/shared/src/main/scala/munit/AfterEach.scala

@@ -0,0 +1,5 @@
+package munit
+
+class AfterEach(
+    val test: Test
+) extends Serializable

munit/shared/src/main/scala/munit/AnyFixture.scala

@@ -0,0 +1,37 @@
+package munit
+
+/**
+ * AnyFixture allows you to acquire resources during setup and clean up resources after the tests finish running.
+ *
+ * Fixtures can be local to a single test case by overriding `beforeEach` and
+ * `afterEach`, or they can be re-used for an entire test suite by extending
+ * `beforeAll` and `afterAll`.
+ *
+ * It's preferable to use a sub-class like `munit.Fixture` or
+ * `munit.FutureFixture` instead of this class.  Extend this class if you're
+ * writing an integration a third-party type like Cats `Resource`.
+ *
+ * @see https://scalameta.org/munit/docs/fixtures.html
+ * @param fixtureName The name of this fixture, used for displaying an error message if
+ * `beforeAll()` or `afterAll()` fail.
+ */
+abstract class AnyFixture[T](val fixtureName: String) {
+
+  /** The value produced by this suite-local fixture that can be reused for all test cases. */
+  def apply(): T
+
+  /** Runs once before the test suite starts */
+  def beforeAll(): Any = ()
+
+  /**
+   * Runs before each individual test case.  An error in this method aborts the test case.
+   */
+  def beforeEach(context: BeforeEach): Any = ()
+
+  /** Runs after each individual test case. */
+  def afterEach(context: AfterEach): Any = ()
+
+  /** Runs once after the test suite has finished, regardless if the tests failed or not. */
+  def afterAll(): Any = ()
+
+}

munit/shared/src/main/scala/munit/BeforeEach.scala

@@ -0,0 +1,5 @@
+package munit
+
+class BeforeEach(
+    val test: Test
+) extends Serializable