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/*
 * Copyright 2001-2014 Artima, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.scalatest

/**
 * Enables testing of asynchronous code without blocking,
 * using a style consistent with traditional FunSuite tests.
 *
 * 
* Recommended Usage: * AsyncFunSuite is intended to enable users of FunSuite * to write non-blocking asynchronous tests that are consistent with their traditional FunSuite tests. * Note: AsyncFunSuite is intended for use in special situations where non-blocking asynchronous * testing is needed, with class FunSuite used for general needs. *
* *

* Given a Future returned by the code you are testing, * you need not block until the Future completes before * performing assertions against its value. You can instead map those * assertions onto the Future and return the resulting * Future[Assertion] to ScalaTest. The test will complete * asynchronously, when the Future[Assertion] completes. *

* *

* Here's an example AsyncFunSuite: *

* *
 * package org.scalatest.examples.asyncfunsuite

 * import org.scalatest.AsyncFunSuite
 * import scala.concurrent.Future
 *
 * class AddSuite extends AsyncFunSuite {
 *
 *   def addSoon(addends: Int*): Future[Int] = Future { addends.sum }
 *
 *   test("addSoon will eventually compute a sum of passed Ints") {
 *     val futureSum: Future[Int] = addSoon(1, 2)
 *     // You can map assertions onto a Future, then return
 *     // the resulting Future[Assertion] to ScalaTest:
 *     futureSum map { sum => assert(sum == 3) }
 *   } 
 *
 *   def addNow(addends: Int*): Int = addends.sum
 *
 *   test("addNow will immediately compute a sum of passed Ints") {
 *     val sum: Int = addNow(1, 2)
 *     // You can also write synchronous tests, which
 *     // must result in type Assertion:
 *     assert(sum == 3)
 *   }
 * }
 * 
* *

* “test” is a method, defined in AsyncFunSuite, which will be invoked * by the primary constructor of AddSuite. You specify the name of the test as * a string between the parentheses, and the test code itself between curly braces. * The test code is a function passed as a by-name parameter to test, which registers * it for later execution. The result type of the by-name in an AsyncFunSuite must * be Future[Assertion]. *

* *

* Starting with version 3.0.0, ScalaTest assertions and matchers have result type Assertion. * The result type of the first test in the example above, therefore, is Future[Assertion]. * For clarity, here's the relevant code in a REPL session: *

* *
 * scala> import org.scalatest._
 * import org.scalatest._
 *
 * scala> import Assertions._
 * import Assertions._
 *
 * scala> import scala.concurrent.Future
 * import scala.concurrent.Future
 *
 * scala> import scala.concurrent.ExecutionContext
 * import scala.concurrent.ExecutionContext
 *
 * scala> implicit val executionContext = ExecutionContext.Implicits.global
 * executionContext: scala.concurrent.ExecutionContextExecutor = scala.concurrent.impl.ExecutionContextImpl@26141c5b
 *
 * scala> def addSoon(addends: Int*): Future[Int] = Future { addends.sum }
 * addSoon: (addends: Int*)scala.concurrent.Future[Int]
 *
 * scala> val futureSum: Future[Int] = addSoon(1, 2)
 * futureSum: scala.concurrent.Future[Int] = scala.concurrent.impl.Promise$DefaultPromise@721f47b2
 *
 * scala> futureSum map { sum => assert(sum == 3) }
 * res0: scala.concurrent.Future[org.scalatest.Assertion] = scala.concurrent.impl.Promise$DefaultPromise@3955cfcb
 * 
* *

* The second test has result type Assertion: *

* *
 * scala> def addNow(addends: Int*): Int = addends.sum
 * addNow: (addends: Int*)Int
 *
 * scala> val sum: Int = addNow(1, 2)
 * sum: Int = 3
 *
 * scala> assert(sum == 3)
 * res1: org.scalatest.Assertion = Succeeded
 * 
* *

* When AddSuite is constructed, the second test will be implicitly converted to * Future[Assertion] and registered. The implicit conversion is from Assertion * to Future[Assertion], so you must end synchronous tests in some ScalaTest assertion * or matcher expression. If a test would not otherwise end in type Assertion, you can * place succeed at the end of the test. succeed, a field in trait Assertions, * returns the Succeeded singleton: *

* *
 * scala> succeed
 * res2: org.scalatest.Assertion = Succeeded
 * 
* *

* Thus placing succeed at the end of a test body will satisfy the type checker: *

* *
 *   test("addNow will immediately compute a sum of passed Ints") {
 *     val sum: Int = addNow(1, 2)
 *     assert(sum == 3)
 *     println("hi") // println has result type Unit
 *     succeed       // succeed has result type Assertion
 *   }
 * 
* *

* An AsyncFunSuite's lifecycle has two phases: the registration phase and the * ready phase. It starts in registration phase and enters ready phase the first time * run is called on it. It then remains in ready phase for the remainder of its lifetime. *

* *

* Tests can only be registered with the test method while the AsyncFunSuite is * in its registration phase. Any attempt to register a test after the AsyncFunSuite has * entered its ready phase, i.e., after run has been invoked on the AsyncFunSuite, * will be met with a thrown TestRegistrationClosedException. The recommended style * of using AsyncFunSuite is to register tests during object construction as is done in all * the examples shown here. If you keep to the recommended style, you should never see a * TestRegistrationClosedException. *

* *

Asynchronous execution model

* *

* AsyncFunSuite extends AsyncTestSuite, which provides an * implicit scala.concurrent.ExecutionContext * named executionContext. This * execution context is used by AsyncFunSuite to * transform the Future[Assertion]s returned by each test * into the FutureOutcome returned by the test function * passed to withFixture. * This ExecutionContext is also intended to be used in the tests, * including when you map assertions onto futures. *

* *

* On both the JVM and Scala.js, the default execution context provided by ScalaTest's asynchronous * testing styles confines execution to a single thread per test. On JavaScript, where single-threaded * execution is the only possibility, the default execution context is * scala.scalajs.concurrent.JSExecutionContext.Implicits.queue. On the JVM, * the default execution context is a serial execution context provided by ScalaTest itself. *

* *

* When ScalaTest's serial execution context is called upon to execute a task, that task is recorded * in a queue for later execution. For example, one task that will be placed in this queue is the * task that transforms the Future[Assertion] returned by an asynchronous test body * to the FutureOutcome returned from the test function. * Other tasks that will be queued are any transformations of, or callbacks registered on, Futures that occur * in your test body, including any assertions you map onto Futures. Once the test body returns, * the thread that executed the test body will execute the tasks in that queue one after another, in the order they * were enqueued. *

* *

* ScalaTest provides its serial execution context as the default on the JVM for three reasons. First, most often * running both tests and suites in parallel does not give a significant performance boost compared to * just running suites in parallel. Thus parallel execution of Future transformations within * individual tests is not generally needed for performance reasons. *

* *

* Second, if multiple threads are operating in the same suite * concurrently, you'll need to make sure access to any mutable fixture objects by multiple threads is synchronized. * Although access to mutable state along * the same linear chain of Future transformations need not be synchronized, * this does not hold true for callbacks, and in general it is easy to make a mistake. Simply put: synchronizing access to * shared mutable state is difficult and error prone. * Because ScalaTest's default execution context on the JVM confines execution of Future transformations * and call backs to a single thread, you need not (by default) worry about synchronizing access to mutable state * in your asynchronous-style tests. *

* *

* Third, asynchronous-style tests need not be complete when the test body returns, because the test body returns * a Future[Assertion]. This Future[Assertion] will often represent a test that has not yet * completed. As a result, when using a more traditional execution context backed by a thread-pool, you could * potentially start many more tests executing concurrently than there are threads in the thread pool. The more * concurrently execute tests you have competing for threads from the same limited thread pool, the more likely it * will be that tests will intermitently fail due to timeouts. *

* *

* Using ScalaTest's serial execution context on the JVM will ensure the same thread that produced the Future[Assertion] * returned from a test body is also used to execute any tasks given to the execution context while executing the test * body—and that thread will not be allowed to do anything else until the test completes. * If the serial execution context's task queue ever becomes empty while the Future[Assertion] returned by * that test's body has not yet completed, the thread will block until another task for that test is enqueued. Although * it may seem counter-intuitive, this blocking behavior means the total number of tests allowed to run concurrently will be limited * to the total number of threads executing suites. This fact means you can tune the thread pool such that maximum performance * is reached while avoiding (or at least, reducing the likelihood of) tests that fail due to timeouts because of thread competition. *

* *

* This thread confinement strategy does mean, however, that when you are using the default execution context on the JVM, you * must be sure to never block in the test body waiting for a task to be completed by the * execution context. If you block, your test will never complete. This kind of problem will be obvious, because the test will * consistently hang every time you run it. (If a test is hanging, and you're not sure which one it is, * enable slowpoke notifications.) If you really do * want to block in your tests, you may wish to just use a * traditional FunSuite with * ScalaFutures instead. Alternatively, you could override * the executionContext and use a traditional ExecutionContext backed by a thread pool. This * will enable you to block in an asynchronous-style test on the JVM, but you'll need to worry about synchronizing access to * shared mutable state. *

* *

* To use a different execution context, just override executionContext. For example, if you prefer to use * the runNow execution context on Scala.js instead of the default queue, you would write: *

* *
 * // on Scala.js
 * implicit override def executionContext =
 *     scala.scalajs.concurrent.JSExecutionContext.Implicits.runNow
 * 
* *

* If you prefer on the JVM to use the global execution context, which is backed by a thread pool, instead of ScalaTest's default * serial execution contex, which confines execution to a single thread, you would write: *

* *
 * // on the JVM (and also compiles on Scala.js, giving
 * // you the queue execution context)
 * implicit override def executionContext =
 *     scala.concurrent.ExecutionContext.Implicits.global
 * 
* *

Serial and parallel test execution

* *

* By default (unless you mix in ParallelTestExecution), tests in an AsyncFunSuite will be executed one after * another, i.e., serially. This is true whether those tests return Assertion or Future[Assertion], * no matter what threads are involved. This default behavior allows * you to re-use a shared fixture, such as an external database that needs to be cleaned * after each test, in multiple tests in async-style suites. This is implemented by registering each test, other than the first test, to run * as a continuation after the previous test completes. *

* *

* If you want the tests of an AsyncFunSuite to be executed in parallel, you * must mix in ParallelTestExecution and enable parallel execution of tests in your build. * You enable parallel execution in Runner with the -P command line flag. * In the ScalaTest Maven Plugin, set parallel to true. * In sbt, parallel execution is the default, but to be explicit you can write: * *

 * parallelExecution in Test := true // the default in sbt
 * 
* * On the JVM, if both ParallelTestExecution is mixed in and * parallel execution is enabled in the build, tests in an async-style suite will be started in parallel, using threads from * the Distributor, and allowed to complete in parallel, using threads from the * executionContext. If you are using ScalaTest's serial execution context, the JVM default, asynchronous tests will * run in parallel very much like traditional (such as FunSuite) tests run in * parallel: 1) Because ParallelTestExecution extends * OneInstancePerTest, each test will run in its own instance of the test class, you need not worry about synchronizing * access to mutable instance state shared by different tests in the same suite. * 2) Because the serial execution context will confine the execution of each test to the single thread that executes the test body, * you need not worry about synchronizing access to shared mutable state accessed by transformations and callbacks of Futures * inside the test. *

* *

* If ParallelTestExecution is mixed in but * parallel execution of suites is not enabled, asynchronous tests on the JVM will be started sequentially, by the single thread * that invoked run, but without waiting for one test to complete before the next test is started. As a result, * asynchronous tests will be allowed to complete in parallel, using threads * from the executionContext. If you are using the serial execution context, however, you'll see * the same behavior you see when parallel execution is disabled and a traditional suite that mixes in ParallelTestExecution * is executed: the tests will run sequentially. If you use an execution context backed by a thread-pool, such as global, * however, even though tests will be started sequentially by one thread, they will be allowed to run concurrently using threads from the * execution context's thread pool. *

* *

* The latter behavior is essentially what you'll see on Scala.js when you execute a suite that mixes in ParallelTestExecution. * Because only one thread exists when running under JavaScript, you can't "enable parallel execution of suites." However, it may * still be useful to run tests in parallel on Scala.js, because tests can invoke API calls that are truly asynchronous by calling into * external APIs that take advantage of non-JavaScript threads. Thus on Scala.js, ParallelTestExecution allows asynchronous * tests to run in parallel, even though they must be started sequentially. This may give you better performance when you are using API * calls in your Scala.js tests that are truly asynchronous. *

* *

Futures and expected exceptions

* *

* If you need to test for expected exceptions in the context of futures, you can use the * recoverToSucceededIf and recoverToExceptionIf methods of trait * RecoverMethods. Because this trait is mixed into * supertrait AsyncTestSuite, both of these methods are * available by default in an AsyncFunSuite. *

* *

* If you just want to ensure that a future fails with a particular exception type, and do * not need to inspect the exception further, use recoverToSucceededIf: *

* *
 * recoverToSucceededIf[IllegalStateException] { // Result type: Future[Assertion]
 *   emptyStackActor ? Peek
 * }
 * 
* *

* The recoverToSucceededIf method performs a job similar to * assertThrows, except * in the context of a future. It transforms a Future of any type into a * Future[Assertion] that succeeds only if the original future fails with the specified * exception. Here's an example in the REPL: *

* *
 * scala> import org.scalatest.RecoverMethods._
 * import org.scalatest.RecoverMethods._
 * 
 * scala> import scala.concurrent.Future
 * import scala.concurrent.Future
 * 
 * scala> import scala.concurrent.ExecutionContext.Implicits.global
 * import scala.concurrent.ExecutionContext.Implicits.global
 * 
 * scala> recoverToSucceededIf[IllegalStateException] {
 *      |   Future { throw new IllegalStateException }
 *      | }
 * res0: scala.concurrent.Future[org.scalatest.Assertion] = ...
 * 
 * scala> res0.value
 * res1: Option[scala.util.Try[org.scalatest.Assertion]] = Some(Success(Succeeded))
 * 
* *

* Otherwise it fails with an error message similar to those given by assertThrows: *

* *
 * scala> recoverToSucceededIf[IllegalStateException] {
 *      |   Future { throw new RuntimeException }
 *      | }
 * res2: scala.concurrent.Future[org.scalatest.Assertion] = ...
 * 
 * scala> res2.value
 * res3: Option[scala.util.Try[org.scalatest.Assertion]] =
 *     Some(Failure(org.scalatest.exceptions.TestFailedException: Expected exception
 *       java.lang.IllegalStateException to be thrown, but java.lang.RuntimeException
 *       was thrown))
 * 
 * scala> recoverToSucceededIf[IllegalStateException] {
 *      |   Future { 42 }
 *      | }
 * res4: scala.concurrent.Future[org.scalatest.Assertion] = ...
 * 
 * scala> res4.value
 * res5: Option[scala.util.Try[org.scalatest.Assertion]] =
 *     Some(Failure(org.scalatest.exceptions.TestFailedException: Expected exception
 *       java.lang.IllegalStateException to be thrown, but no exception was thrown))
 * 
* *

* The recoverToExceptionIf method differs from the recoverToSucceededIf in * its behavior when the assertion succeeds: recoverToSucceededIf yields a Future[Assertion], * whereas recoverToExceptionIf yields a Future[T], where T is the * expected exception type. *

* *
 * recoverToExceptionIf[IllegalStateException] { // Result type: Future[IllegalStateException]
 *   emptyStackActor ? Peek
 * }
 * 
* *

* In other words, recoverToExpectionIf is to * intercept as * recovertToSucceededIf is to assertThrows. The first one allows you to * perform further assertions on the expected exception. The second one gives you a result type that will satisfy the type checker * at the end of the test body. Here's an example showing recoverToExceptionIf in the REPL: *

* *
 * scala> val futureEx =
 *      |   recoverToExceptionIf[IllegalStateException] {
 *      |     Future { throw new IllegalStateException("hello") }
 *      |   }
 * futureEx: scala.concurrent.Future[IllegalStateException] = ...
 * 
 * scala> futureEx.value
 * res6: Option[scala.util.Try[IllegalStateException]] =
 *     Some(Success(java.lang.IllegalStateException: hello))
 * 
 * scala> futureEx map { ex => assert(ex.getMessage == "world") }
 * res7: scala.concurrent.Future[org.scalatest.Assertion] = ...
 * 
 * scala> res7.value
 * res8: Option[scala.util.Try[org.scalatest.Assertion]] =
 *     Some(Failure(org.scalatest.exceptions.TestFailedException: "[hello]" did not equal "[world]"))
 * 
* *

Ignored tests

* *

* To support the common use case of temporarily disabling a test, with the * good intention of resurrecting the test at a later time, AsyncFunSuite provides registration * methods that start with ignore instead of test. Here's an example: *

* *
 * package org.scalatest.examples.asyncfunsuite.ignore
 *
 * import org.scalatest.AsyncFunSuite
 * import scala.concurrent.Future
 *
 * class AddSuite extends AsyncFunSuite {
 *
 *   def addSoon(addends: Int*): Future[Int] = Future { addends.sum }
 *
 *   ignore("addSoon will eventually compute a sum of passed Ints") {
 *     val futureSum: Future[Int] = addSoon(1, 2)
 *     // You can map assertions onto a Future, then return
 *     // the resulting Future[Assertion] to ScalaTest:
 *     futureSum map { sum => assert(sum == 3) }
 *   }
 *
 *   def addNow(addends: Int*): Int = addends.sum
 *
 *   test("addNow will immediately compute a sum of passed Ints") {
 *     val sum: Int = addNow(1, 2)
 *     // You can also write synchronous tests. The body
 *     // must have result type Assertion:
 *     assert(sum == 3)
 *   }
 * }
 * 
* *

* If you run this version of AddSuite with: *

* *
 * scala> org.scalatest.run(new AddSuite)
 * 
* *

* It will run only the second test and report that the first test was ignored: *

* *
 * AddSuite:
 * - addSoon will eventually compute a sum of passed Ints !!! IGNORED !!!
 * - addNow will immediately compute a sum of passed Ints
 * 
* *

* If you wish to temporarily ignore an entire suite of tests, you can (on the JVM, not Scala.js) annotate the test class with @Ignore, like this: *

* *
 * package org.scalatest.examples.asyncfunsuite.ignoreall
 *
 * import org.scalatest.AsyncFunSuite
 * import scala.concurrent.Future
 * import org.scalatest.Ignore
 *
 * @Ignore
 * class AddSuite extends AsyncFunSuite {
 *
 *   def addSoon(addends: Int*): Future[Int] = Future { addends.sum }
 *
 *   test("addSoon will eventually compute a sum of passed Ints") {
 *     val futureSum: Future[Int] = addSoon(1, 2)
 *     // You can map assertions onto a Future, then return
 *     // the resulting Future[Assertion] to ScalaTest:
 *     futureSum map { sum => assert(sum == 3) }
 *   }
 *
 *   def addNow(addends: Int*): Int = addends.sum
 *
 *   test("addNow will immediately compute a sum of passed Ints") {
 *     val sum: Int = addNow(1, 2)
 *     // You can also write synchronous tests. The body
 *     // must have result type Assertion:
 *     assert(sum == 3)
 *   }
 * }
 * 
* *

* When you mark a test class with a tag annotation, ScalaTest will mark each test defined in that class with that tag. * Thus, marking the AddSuite in the above example with the @Ignore tag annotation means that both tests * in the class will be ignored. If you run the above AddSuite in the Scala interpreter, you'll see: *

* *
 * scala> org.scalatest.run(new AddSuite)
 * AddSuite:
 * - addSoon will eventually compute a sum of passed Ints !!! IGNORED !!!
 * - addNow will immediately compute a sum of passed Ints !!! IGNORED !!!
 * 
* *

* Note that marking a test class as ignored won't prevent it from being discovered by ScalaTest. Ignored classes * will be discovered and run, and all their tests will be reported as ignored. This is intended to keep the ignored * class visible, to encourage the developers to eventually fix and “un-ignore” it. If you want to * prevent a class from being discovered at all (on the JVM, not Scala.js), use the DoNotDiscover * annotation instead. *

* *

* If you want to ignore all tests of a suite on Scala.js, where annotations can't be inspected at runtime, you'll need * to change test to ignore at each test site. To make a suite non-discoverable on Scala.js, ensure it * does not declare a public no-arg constructor. You can either declare a public constructor that takes one or more * arguments, or make the no-arg constructor non-public. Because this technique will also make the suite non-discoverable * on the JVM, it is a good approach for suites you want to run (but not be discoverable) on both Scala.js and the JVM. *

* *

Informers

* *

* One of the parameters to AsyncFunSuite's run method is a Reporter, which * will collect and report information about the running suite of tests. * Information about suites and tests that were run, whether tests succeeded or failed, * and tests that were ignored will be passed to the Reporter as the suite runs. * Most often the reporting done by default by AsyncFunSuite's methods will be sufficient, but * occasionally you may wish to provide custom information to the Reporter from a test. * For this purpose, an Informer that will forward information * to the current Reporter is provided via the info parameterless method. * You can pass the extra information to the Informer via its apply method. * The Informer will then pass the information to the Reporter via an InfoProvided event. * Here's an example that shows both a direct use as well as an indirect use through the methods * of GivenWhenThen: *

* *
 * package org.scalatest.examples.asyncfunsuite.info
 *
 * import collection.mutable
 * import org.scalatest._
 * 
 * class SetSuite extends AsyncFunSuite with GivenWhenThen {
 *
 *   test("An element can be added to an empty mutable Set") {
 *
 *     Given("an empty mutable Set")
 *     val set = mutable.Set.empty[String]
 *
 *     When("an element is added")
 *     set += "clarity"
 *
 *     Then("the Set should have size 1")
 *     assert(set.size === 1)
 *
 *     And("the Set should contain the added element")
 *     assert(set.contains("clarity"))
 *
 *     info("That's all folks!")
 *     succeed
 *   }
 * }
 * 
* * * If you run this AsyncFunSuite from the interpreter, you will see the following output: * *
 * scala> org.scalatest.run(new SetSuite)
 * SetSuite:
 * - an element can be added to an empty mutable Set
 *   + Given an empty mutable Set 
 *   + When an element is added 
 *   + Then the Set should have size 1 
 *   + And the Set should contain the added element 
 *   + That's all folks!
 * 
* *

Documenters

* *

* AsyncFunSuite also provides a markup method that returns a Documenter, which allows you to send * to the Reporter text formatted in Markdown syntax. * You can pass the extra information to the Documenter via its apply method. * The Documenter will then pass the information to the Reporter via an MarkupProvided event. *

* *

* Here's an example AsyncFunSuite that uses markup: *

* *
 * package org.scalatest.examples.asyncfunsuite.markup
 *
 * import collection.mutable
 * import org.scalatest._
 *
 * class SetSuite extends AsyncFunSuite with GivenWhenThen {
 *
 *   markup { """
 *
 * Mutable Set
 * -----------
 *
 * A set is a collection that contains no duplicate elements.
 *
 * To implement a concrete mutable set, you need to provide implementations
 * of the following methods:
 *
 *     def contains(elem: A): Boolean
 *     def iterator: Iterator[A]
 *     def += (elem: A): this.type
 *     def -= (elem: A): this.type
 *
 * If you wish that methods like `take`,
 * `drop`, `filter` return the same kind of set,
 * you should also override:
 *
 *     def empty: This
 *
 * It is also good idea to override methods `foreach` and
 * `size` for efficiency.
 *
 *   """ }
 *
 *   test("An element can be added to an empty mutable Set") {
 *
 *     Given("an empty mutable Set")
 *     val set = mutable.Set.empty[String]
 *
 *     When("an element is added")
 *     set += "clarity"
 *
 *     Then("the Set should have size 1")
 *     assert(set.size === 1)
 *
 *     And("the Set should contain the added element")
 *     assert(set.contains("clarity"))
 *
 *     markup("This test finished with a **bold** statement!")
 *     succeed
 *   }
 * }
 * 
* *

* Although all of ScalaTest's built-in reporters will display the markup text in some form, * the HTML reporter will format the markup information into HTML. Thus, the main purpose of markup is to * add nicely formatted text to HTML reports. Here's what the above SetSpec would look like in the HTML reporter: *

* * * *

Notifiers and alerters

* *

* ScalaTest records text passed to info and markup during tests, and sends the recorded text in the recordedEvents field of * test completion events like TestSucceeded and TestFailed. This allows string reporters (like the standard out reporter) to show * info and markup text after the test name in a color determined by the outcome of the test. For example, if the test fails, string * reporters will show the info and markup text in red. If a test succeeds, string reporters will show the info * and markup text in green. While this approach helps the readability of reports, it means that you can't use info to get status * updates from long running tests. *

* *

* To get immediate (i.e., non-recorded) notifications from tests, you can use note (a Notifier) and alert * (an Alerter). Here's an example showing the differences: *

* *
 * package org.scalatest.examples.asyncfunsuite.note
 *
 * import collection.mutable
 * import org.scalatest._
 *
 * class SetSuite extends AsyncFunSuite {
 *
 *   test("An element can be added to an empty mutable Set") {
 *
 *     info("info is recorded")
 *     markup("markup is *also* recorded")
 *     note("notes are sent immediately")
 *     alert("alerts are also sent immediately")
 *
 *     val set = mutable.Set.empty[String]
 *     set += "clarity"
 *     assert(set.size === 1)
 *     assert(set.contains("clarity"))
 *   }
 * }
 * 
* *

* Because note and alert information is sent immediately, it will appear before the test name in string reporters, and its color will * be unrelated to the ultimate outcome of the test: note text will always appear in green, alert text will always appear in yellow. * Here's an example: *

* *
 * scala> org.scalatest.run(new SetSpec)
 * SetSuite:
 *   + notes are sent immediately
 *   + alerts are also sent immediately
 * - An element can be added to an empty mutable Set
 *   + info is recorded
 *   + markup is *also* recorded
 * 
* *

* Another example is slowpoke notifications. * If you find a test is taking a long time to complete, but you're not sure which test, you can enable * slowpoke notifications. ScalaTest will use an Alerter to fire an event whenever a test has been running * longer than a specified amount of time. *

* *

* In summary, use info and markup for text that should form part of the specification output. Use * note and alert to send status notifications. (Because the HTML reporter is intended to produce a * readable, printable specification, info and markup text will appear in the HTML report, but * note and alert text will not.) *

* * *

Pending tests

* *

* A pending test is one that has been given a name but is not yet implemented. The purpose of * pending tests is to facilitate a style of testing in which documentation of behavior is sketched * out before tests are written to verify that behavior (and often, before the behavior of * the system being tested is itself implemented). Such sketches form a kind of specification of * what tests and functionality to implement later. *

* *

* To support this style of testing, a test can be given a name that specifies one * bit of behavior required by the system being tested. At the end of the test, * it can call method pending, which will cause it to complete abruptly with TestPendingException. *

* *

* Because tests in ScalaTest can be designated as pending with TestPendingException, both the test name and any information * sent to the reporter when running the test can appear in the report of a test run. (In other words, * the code of a pending test is executed just like any other test.) However, because the test completes abruptly * with TestPendingException, the test will be reported as pending, to indicate * the actual test, and possibly the functionality, has not yet been implemented. Here's an example: *

* *
 * package org.scalatest.examples.asyncfunsuite.pending
 *
 * import org.scalatest.AsyncFunSuite
 * import scala.concurrent.Future
 *
 * class AddSuite extends AsyncFunSuite {
 *
 *   def addSoon(addends: Int*): Future[Int] = Future { addends.sum }
 *
 *   test("addSoon will eventually compute a sum of passed Ints") (pending)
 *
 *   def addNow(addends: Int*): Int = addends.sum
 *
 *   test("addNow will immediately compute a sum of passed Ints") {
 *     val sum: Int = addNow(1, 2)
 *     // You can also write synchronous tests. The body
 *     // must have result type Assertion:
 *     assert(sum == 3)
 *   }
 * }
 * 
* *

* (Note: "(pending)" is the body of the test. Thus the test contains just one statement, an invocation * of the pending method, which throws TestPendingException.) * If you run this version of AddSuite with: *

* *
 * scala> org.scalatest.run(new AddSuite)
 * 
* *

* It will run both tests, but report that first test is pending. You'll see: *

* *
 * AddSuite:
 * - addSoon will eventually compute a sum of passed Ints (pending)
 * - addNow will immediately compute a sum of passed Ints
 * 
* *

* One difference between an ignored test and a pending one is that an ignored test is intended to be used during * significant refactorings of the code under test, when tests break and you don't want to spend the time to fix * all of them immediately. You can mark some of those broken tests as ignored temporarily, so that you can focus the red * bar on just failing tests you actually want to fix immediately. Later you can go back and fix the ignored tests. * In other words, by ignoring some failing tests temporarily, you can more easily notice failed tests that you actually * want to fix. By contrast, a pending test is intended to be used before a test and/or the code under test is written. * Pending indicates you've decided to write a test for a bit of behavior, but either you haven't written the test yet, or * have only written part of it, or perhaps you've written the test but don't want to implement the behavior it tests * until after you've implemented a different bit of behavior you realized you need first. Thus ignored tests are designed * to facilitate refactoring of existing code whereas pending tests are designed to facilitate the creation of new code. *

* *

* One other difference between ignored and pending tests is that ignored tests are implemented as a test tag that is * excluded by default. Thus an ignored test is never executed. By contrast, a pending test is implemented as a * test that throws TestPendingException (which is what calling the pending method does). Thus * the body of pending tests are executed up until they throw TestPendingException. *

* *

Tagging tests

* *

* An AsyncFunSuite's tests may be classified into groups by tagging them with string names. * As with any suite, when executing an AsyncFunSuite, groups of tests can * optionally be included and/or excluded. To tag an AsyncFunSuite's tests, * you pass objects that extend class org.scalatest.Tag to methods * that register tests. Class Tag takes one parameter, a string name. If you have * created tag annotation interfaces as described in the Tag documentation, then you * will probably want to use tag names on your test functions that match. To do so, simply * pass the fully qualified names of the tag interfaces to the Tag constructor. For example, if you've * defined a tag annotation interface with fully qualified name, * com.mycompany.tags.DbTest, then you could * create a matching tag for AsyncFunSuites like this: *

* *
 * package org.scalatest.examples.asyncfunsuite.tagging
 *
 * import org.scalatest.Tag
 *
 * object DbTest extends Tag("com.mycompany.tags.DbTest")
 * 
* *

* Given these definitions, you could place AsyncFunSuite tests into groups with tags like this: *

* *
 * import org.scalatest.AsyncFunSuite
 * import org.scalatest.tagobjects.Slow
 * import scala.concurrent.Future
 *
 * class AddSuite extends AsyncFunSuite {
 *
 *   def addSoon(addends: Int*): Future[Int] = Future { addends.sum }
 *
 *   test("addSoon will eventually compute a sum of passed Ints", Slow) {
 *     val futureSum: Future[Int] = addSoon(1, 2)
 *     // You can map assertions onto a Future, then return
 *     // the resulting Future[Assertion] to ScalaTest:
 *     futureSum map { sum => assert(sum == 3) }
 *   }
 *
 *   def addNow(addends: Int*): Int = addends.sum
 *
 *   test("addNow will immediately compute a sum of passed Ints",
 *       Slow, DbTest) {
 *
 *     val sum: Int = addNow(1, 2)
 *     // You can also write synchronous tests. The body
 *     // must have result type Assertion:
 *     assert(sum == 3)
 *   }
 * }
 * 
* *

* This code marks both tests with the org.scalatest.tags.Slow tag, * and the second test with the com.mycompany.tags.DbTest tag. *

* *

* The run method takes a Filter, whose constructor takes an optional * Set[String] called tagsToInclude and a Set[String] called * tagsToExclude. If tagsToInclude is None, all tests will be run * except those those belonging to tags listed in the * tagsToExclude Set. If tagsToInclude is defined, only tests * belonging to tags mentioned in the tagsToInclude set, and not mentioned in tagsToExclude, * will be run. *

* *

* It is recommended, though not required, that you create a corresponding tag annotation when you * create a Tag object. A tag annotation (on the JVM, not Scala.js) allows you to tag all the tests of an AsyncFunSuite in * one stroke by annotating the class. For more information and examples, see the * documentation for class Tag. On Scala.js, to tag all tests of a suite, you'll need to * tag each test individually at the test site. *

* * *

Shared fixtures

* *

* A test fixture is composed of the objects and other artifacts (files, sockets, database * connections, etc.) tests use to do their work. * When multiple tests need to work with the same fixtures, it is important to try and avoid * duplicating the fixture code across those tests. The more code duplication you have in your * tests, the greater drag the tests will have on refactoring the actual production code. *

* *

* ScalaTest recommends three techniques to eliminate such code duplication in async styles: *

* *
    *
  • Refactor using Scala
  • *
  • Override withFixture
  • *
  • Mix in a before-and-after trait
  • *
* *

Each technique is geared towards helping you reduce code duplication without introducing * instance vars, shared mutable objects, or other dependencies between tests. Eliminating shared * mutable state across tests will make your test code easier to reason about and eliminate the need to * synchronize access to shared mutable state on the JVM. *

* *

* The following sections describe these techniques, including explaining the recommended usage * for each. But first, here's a table summarizing the options:

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* Refactor using Scala when different tests need different fixtures. *
* get-fixture methods * * The extract method refactor helps you create a fresh instances of mutable fixture objects in each test * that needs them, but doesn't help you clean them up when you're done. *
* loan-fixture methods * * Factor out dupicate code with the loan pattern when different tests need different fixtures that must be cleaned up afterwards. *
* Override withFixture when most or all tests need the same fixture. *
* * withFixture(NoArgAsyncTest) * *

* The recommended default approach when most or all tests need the same fixture treatment. This general technique * allows you, for example, to perform side effects at the beginning and end of all or most tests, * transform the outcome of tests, retry tests, make decisions based on test names, tags, or other test data. * Use this technique unless: *

*
*
Different tests need different fixtures (refactor using Scala instead)
*
An exception in fixture code should abort the suite, not fail the test (use a before-and-after trait instead)
*
You have objects to pass into tests (override withFixture(OneArgAsyncTest) instead)
*
*
* * withFixture(OneArgAsyncTest) * * * Use when you want to pass the same fixture object or objects as a parameter into all or most tests. *
* Mix in a before-and-after trait when you want an aborted suite, not a failed test, if the fixture code fails. *
* BeforeAndAfter * * Use this boilerplate-buster when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests. *
* BeforeAndAfterEach * * Use when you want to stack traits that perform the same side-effects before and/or after tests, rather than at the beginning or end of tests. *
* * *

Calling get-fixture methods

* *

* If you need to create the same mutable fixture objects in multiple tests, and don't need to clean them up after using them, the simplest approach is to write one or * more get-fixture methods. A get-fixture method returns a new instance of a needed fixture object (or a holder object containing * multiple fixture objects) each time it is called. You can call a get-fixture method at the beginning of each * test that needs the fixture, storing the returned object or objects in local variables. Here's an example: *

* *
 * package org.scalatest.examples.asyncfunsuite.getfixture

 * import org.scalatest.AsyncFunSuite
 * import collection.mutable.ListBuffer
 * import scala.concurrent.Future
 *
 * class ExampleSuite extends AsyncFunSuite {
 *
 *   def fixture: Future[String] = Future { "ScalaTest is " }
 *
 *   test("Testing should be easy") {
 *     val future = fixture
 *     val result = future map { s => s + "easy!" }
 *     result map { s =>
 *       assert(s === "ScalaTest is easy!")
 *     }
 *   }
 *
 *   test("Testing should be fun") {
 *     val future = fixture
 *     val result = future map { s => s + "fun!" }
 *     result map { s =>
 *       assert(s === "ScalaTest is fun!")
 *     }
 *   }
 * }
 * 
* *

* If you need to configure fixture objects differently in different tests, you can pass configuration into the get-fixture method. * For example, you could pass in an initial value for a fixture object as a parameter to the get-fixture method. *

* * *

Overriding withFixture(NoArgAsyncTest)

* *

* Although the get-fixture method approach takes care of setting up a fixture at the beginning of each * test, it doesn't address the problem of cleaning up a fixture at the end of the test. If you just need to perform a side-effect at the beginning or end of * a test, and don't need to actually pass any fixture objects into the test, you can override withFixture(NoArgAsyncTest), a * method defined in trait AsyncTestSuite, a supertrait of AsyncFunSuite. *

* *

* Trait AsyncFunSuite's runTest method passes a no-arg async test function to * withFixture(NoArgAsyncTest). It is withFixture's * responsibility to invoke that test function. The default implementation of withFixture simply * invokes the function and returns the result, like this: *

* *
 * // Default implementation in trait AsyncTestSuite
 * protected def withFixture(test: NoArgAsyncTest): FutureOutcome = {
 *   test()
 * }
 * 
* *

* You can, therefore, override withFixture to perform setup before invoking the test function, * and/or perform cleanup after the test completes. The recommended way to ensure cleanup is performed after a test completes is * to use the complete-lastly syntax, defined in supertrait CompleteLastly. * The complete-lastly syntax will ensure that * cleanup will occur whether future-producing code completes abruptly by throwing an exception, or returns * normally yielding a future. In the latter case, complete-lastly will register the cleanup code * to execute asynchronously when the future completes. *

* *

* The withFixture method is designed to be stacked, and to enable this, you should always call the super implementation * of withFixture, and let it invoke the test function rather than invoking the test function directly. In other words, instead of writing * “test()”, you should write “super.withFixture(test)”, like this: *

* *
 * // Your implementation
 * override def withFixture(test: NoArgAsyncTest) = {
 *
 *   // Perform setup here
 * 
 *   complete {
 *     super.withFixture(test) // Invoke the test function
 *   } lastly {
 *     // Perform cleanup here
 *   }
 * }
 * 
* *

* If you have no cleanup to perform, you can write withFixture like this instead: *

* *
 * // Your implementation
 * override def withFixture(test: NoArgAsyncTest) = {
 *
 *   // Perform setup here
 *
 *   super.withFixture(test) // Invoke the test function
 * }
 * 
* *

* If you want to perform an action only for certain outcomes, you'll need to * register code performing that action as a callback on the Future using * one of Future's registration methods: onComplete, onSuccess, * or onFailure. Note that if a test fails, that will be treated as a * scala.util.Success(org.scalatest.Failed). So if you want to perform an * action if a test fails, for example, you'd register the callback using onSuccess. *

* *

* Here's an example in which withFixture(NoArgAsyncTest) is used to take a * snapshot of the working directory if a test fails, and * send that information to the standard output stream: *

* *
 * package org.scalatest.examples.asyncfunsuite.noargasynctest
 *
 * import java.io.File
 * import org.scalatest._
 * import scala.concurrent.Future
 *
 * class ExampleSuite extends AsyncFunSuite {
 *
 *   override def withFixture(test: NoArgAsyncTest) = {
 *
 *     super.withFixture(test) onFailedThen { _ =>
 *       val currDir = new File(".")
 *       val fileNames = currDir.list()
 *       info("Dir snapshot: " + fileNames.mkString(", "))
 *     }
 *   }
 *
 *   def addSoon(addends: Int*): Future[Int] = Future { addends.sum }
 *
 *   test("This test should succeed") {
 *     addSoon(1, 1) map { sum => assert(sum === 2) }
 *   }
 *
 *   test("This test should fail") {
 *     addSoon(1, 1) map { sum => assert(sum === 3) }
 *   }
 * }
 * 
* *

* Running this version of ExampleSuite in the interpreter in a directory with two files, hello.txt and world.txt * would give the following output: *

* *
 * scala> org.scalatest.run(new ExampleSuite)
 * ExampleSuite:
 * - this test should succeed
 * Dir snapshot: hello.txt, world.txt
 * - this test should fail *** FAILED ***
 *   2 did not equal 3 (:33)
 * 
* *

* Note that the NoArgAsyncTest passed to withFixture, in addition to * an apply method that executes the test, also includes the test name and the config * map passed to runTest. Thus you can also use the test name and configuration objects in your withFixture * implementation. *

* *

* Lastly, if you want to transform the outcome in some way in withFixture, you'll need to use either the * map or transform methods of Future, like this: *

* *
 * // Your implementation
 * override def withFixture(test: NoArgAsyncTest) = {
 *
 *   // Perform setup here
 *
 *   val futureOutcome = super.withFixture(test) // Invoke the test function
 *
 *   futureOutcome change { outcome =>
 *     // transform the outcome into a new outcome here
 *   }
 * }
 * 
* *

* Note that a NoArgAsyncTest's apply method will return a scala.util.Failure only if * the test completes abruptly with a "test-fatal" exception (such as OutOfMemoryError) that should * cause the suite to abort rather than the test to fail. Thus usually you would use map * to transform future outcomes, not transform, so that such test-fatal exceptions pass through * unchanged. The suite will abort asynchronously with any exception returned from NoArgAsyncTest's * apply method in a scala.util.Failure. *

* * *

Calling loan-fixture methods

* *

* If you need to both pass a fixture object into a test and perform cleanup at the end of the test, you'll need to use the loan pattern. * If different tests need different fixtures that require cleanup, you can implement the loan pattern directly by writing loan-fixture methods. * A loan-fixture method takes a function whose body forms part or all of a test's code. It creates a fixture, passes it to the test code by invoking the * function, then cleans up the fixture after the function returns. *

* *

* The following example shows three tests that use two fixtures, a database and a file. Both require cleanup after, so each is provided via a * loan-fixture method. (In this example, the database is simulated with a StringBuffer.) *

* *
 * package org.scalatest.examples.asyncfunsuite.loanfixture
 *
 * import java.util.concurrent.ConcurrentHashMap
 *
 * import scala.concurrent.Future
 * import scala.concurrent.ExecutionContext
 *
 * object DbServer { // Simulating a database server
 *   type Db = StringBuffer
 *   private final val databases = new ConcurrentHashMap[String, Db]
 *   def createDb(name: String): Db = {
 *     val db = new StringBuffer // java.lang.StringBuffer is thread-safe
 *     databases.put(name, db)
 *     db
 *   }
 *   def removeDb(name: String): Unit = {
 *     databases.remove(name)
 *   }
 * }
 *
 * // Defining actor messages
 * sealed abstract class StringOp
 * case object Clear extends StringOp
 * case class Append(value: String) extends StringOp
 * case object GetValue
 *
 * class StringActor { // Simulating an actor
 *   private final val sb = new StringBuilder
 *   def !(op: StringOp): Unit =
 *     synchronized {
 *       op match {
 *         case Append(value) => sb.append(value)
 *         case Clear => sb.clear()
 *       }
 *     }
 *   def ?(get: GetValue.type)(implicit c: ExecutionContext): Future[String] =
 *     Future {
 *       synchronized { sb.toString }
 *     }
 * }
 *
 * import org.scalatest._
 * import DbServer._
 * import java.util.UUID.randomUUID
 *
 * class ExampleSuite extends AsyncFunSuite {
 *
 *   def withDatabase(testCode: Future[Db] => Future[Assertion]) = {
 *     val dbName = randomUUID.toString // generate a unique db name
 *     val futureDb = Future { createDb(dbName) } // create the fixture
 *     complete {
 *       val futurePopulatedDb =
 *         futureDb map { db =>
 *           db.append("ScalaTest is ") // perform setup 
 *         }
 *       testCode(futurePopulatedDb) // "loan" the fixture to the test code
 *     } lastly {
 *       removeDb(dbName) // ensure the fixture will be cleaned up
 *     }
 *   }
 *
 *   def withActor(testCode: StringActor => Future[Assertion]) = {
 *     val actor = new StringActor
 *     complete {
 *       actor ! Append("ScalaTest is ") // set up the fixture
 *       testCode(actor) // "loan" the fixture to the test code
 *     } lastly {
 *       actor ! Clear // ensure the fixture will be cleaned up
 *     }
 *   }
 *
 *   // This test needs the actor fixture
 *   test("Testing should be productive") {
 *     withActor { actor =>
 *       actor ! Append("productive!")
 *       val futureString = actor ? GetValue
 *       futureString map { s =>
 *         assert(s === "ScalaTest is productive!")
 *       }
 *     }
 *   }
 *
 *   // This test needs the database fixture
 *   test("Test code should be readable") {
 *     withDatabase { futureDb =>
 *       futureDb map { db =>
 *         db.append("readable!")
 *         assert(db.toString === "ScalaTest is readable!")
 *       }
 *     }
 *   }
 *
 *   // This test needs both the actor and the database
 *   test("Test code should be clear and concise") {
 *     withDatabase { futureDb =>
 *       withActor { actor => // loan-fixture methods compose
 *         actor ! Append("concise!")
 *         val futureString = actor ? GetValue
 *         val futurePair: Future[(Db, String)] =
 *           futureDb zip futureString
 *         futurePair map { case (db, s) =>
 *           db.append("clear!")
 *           assert(db.toString === "ScalaTest is clear!")
 *           assert(s === "ScalaTest is concise!")
 *         }
 *       }
 *     }
 *   }
 * }
 * 
* *

* As demonstrated by the last test, loan-fixture methods compose. Not only do loan-fixture methods allow you to * give each test the fixture it needs, they allow you to give a test multiple fixtures and clean everything up afterwards. *

* *

* Also demonstrated in this example is the technique of giving each test its own "fixture sandbox" to play in. When your fixtures * involve external side-effects, like creating databases, it is a good idea to give each database a unique name as is * done in this example. This keeps tests completely isolated, allowing you to run them in parallel if desired. *

* * *

Overriding withFixture(OneArgTest)

* *

* If all or most tests need the same fixture, you can avoid some of the boilerplate of the loan-fixture method approach by using a * fixture.AsyncTestSuite and overriding withFixture(OneArgAsyncTest). * Each test in a fixture.AsyncTestSuite takes a fixture as a parameter, allowing you to pass the fixture into * the test. You must indicate the type of the fixture parameter by specifying FixtureParam, and implement a * withFixture method that takes a OneArgAsyncTest. This withFixture method is responsible for * invoking the one-arg async test function, so you can perform fixture set up before invoking and passing * the fixture into the test function, and ensure clean up is performed after the test completes. *

* *

* To enable the stacking of traits that define withFixture(NoArgAsyncTest), it is a good idea to let * withFixture(NoArgAsyncTest) invoke the test function instead of invoking the test * function directly. To do so, you'll need to convert the OneArgAsyncTest to a NoArgAsyncTest. You can do that by passing * the fixture object to the toNoArgAsyncTest method of OneArgAsyncTest. In other words, instead of * writing “test(theFixture)”, you'd delegate responsibility for * invoking the test function to the withFixture(NoArgAsyncTest) method of the same instance by writing: *

* *
 * withFixture(test.toNoArgAsyncTest(theFixture))
 * 
* *

* Here's a complete example: *

* *
 * package org.scalatest.examples.asyncfunsuite.oneargasynctest
 * 
 * import org.scalatest._
 * import java.io._
 * import scala.concurrent.Future
 * import scala.concurrent.ExecutionContext
 * 
 * // Defining actor messages
 * sealed abstract class StringOp
 * case object Clear extends StringOp
 * case class Append(value: String) extends StringOp
 * case object GetValue
 * 
 * class StringActor { // Simulating an actor
 *   private final val sb = new StringBuilder
 *   def !(op: StringOp): Unit =
 *     synchronized {
 *       op match {
 *         case Append(value) => sb.append(value)
 *         case Clear => sb.clear()
 *       }
 *     }
 *   def ?(get: GetValue.type)(implicit c: ExecutionContext): Future[String] =
 *     Future {
 *       synchronized { sb.toString }
 *     }
 * }
 * 
 * class ExampleSuite extends fixture.AsyncFunSuite {
 * 
 *   type FixtureParam = StringActor
 * 
 *   def withFixture(test: OneArgAsyncTest): FutureOutcome = {
 * 
 *     val actor = new StringActor
 *     complete {
 *       actor ! Append("ScalaTest is ") // set up the fixture
 *       withFixture(test.toNoArgAsyncTest(actor))
 *     } lastly {
 *       actor ! Clear // ensure the fixture will be cleaned up
 *     }
 *   }
 * 
 *   test("Testing should be easy") { actor =>
 *     actor ! Append("easy!")
 *     val futureString = actor ? GetValue
 *     futureString map { s =>
 *       assert(s === "ScalaTest is easy!")
 *     }
 *   }
 * 
 *   test("Testing should be fun") { actor =>
 *     actor ! Append("fun!")
 *     val futureString = actor ? GetValue
 *     futureString map { s =>
 *       assert(s === "ScalaTest is fun!")
 *     }
 *   }
 * }
 * 
* *

* In this example, the tests required one fixture object, a StringActor. If your tests need multiple fixture objects, you can * simply define the FixtureParam type to be a tuple containing the objects or, alternatively, a case class containing * the objects. For more information on the withFixture(OneArgAsyncTest) technique, see * the documentation for fixture.AsyncFunSuite. *

* * *

Mixing in BeforeAndAfter

* *

* In all the shared fixture examples shown so far, the activities of creating, setting up, and cleaning up the fixture objects have been * performed during the test. This means that if an exception occurs during any of these activities, it will be reported as a test failure. * Sometimes, however, you may want setup to happen before the test starts, and cleanup after the test has completed, so that if an * exception occurs during setup or cleanup, the entire suite aborts and no more tests are attempted. The simplest way to accomplish this in ScalaTest is * to mix in trait BeforeAndAfter. With this trait you can denote a bit of code to run before each test * with before and/or after each test each test with after, like this: *

* *
 * package org.scalatest.examples.asyncfunsuite.beforeandafter
 * 
 * import org.scalatest.AsyncFunSuite
 * import org.scalatest.BeforeAndAfter
 * import collection.mutable.ListBuffer
 * import scala.concurrent.Future
 * import scala.concurrent.ExecutionContext
 * 
 * // Defining actor messages
 * sealed abstract class StringOp
 * case object Clear extends StringOp
 * case class Append(value: String) extends StringOp
 * case object GetValue
 * 
 * class StringActor { // Simulating an actor
 *   private final val sb = new StringBuilder
 *   def !(op: StringOp): Unit =
 *     synchronized {
 *       op match {
 *         case Append(value) => sb.append(value)
 *         case Clear => sb.clear()
 *       }
 *     }
 *   def ?(get: GetValue.type)(implicit c: ExecutionContext): Future[String] =
 *     Future {
 *       synchronized { sb.toString }
 *     }
 * }
 * 
 * class ExampleSuite extends AsyncFunSuite with BeforeAndAfter {
 * 
 *   final val actor = new StringActor
 * 
 *   before {
 *     actor ! Append("ScalaTest is ") // set up the fixture
 *   }
 * 
 *   after {
 *     actor ! Clear // clean up the fixture
 *   }
 * 
 *   test("testing should be easy") {
 *     actor ! Append("easy!")
 *     val futureString = actor ? GetValue
 *     futureString map { s =>
 *       assert(s === "ScalaTest is easy!")
 *     }
 *   }
 * 
 *   test("testing should be fun") {
 *     actor ! Append("fun!")
 *     val futureString = actor ? GetValue
 *     futureString map { s =>
 *       assert(s === "ScalaTest is fun!")
 *     }
 *   }
 * }
 * 
* *

* Note that the only way before and after code can communicate with test code is via some * side-effecting mechanism, commonly by reassigning instance vars or by changing the state of mutable * objects held from instance vals (as in this example). If using instance vars or * mutable objects held from instance vals you wouldn't be able to run tests in parallel in the same instance * of the test class (on the JVM, not Scala.js) unless you synchronized access to the shared, mutable state. *

* *

* Note that on the JVM, if you override ScalaTest's default * serial execution context, you will likely need to * worry about synchronizing access to shared mutable fixture state, because the execution * context may assign different threads to process * different Future transformations. Although access to mutable state along * the same linear chain of Future transformations need not be synchronized, * it can be difficult to spot cases where these constraints are violated. The best approach * is to use only immutable objects when transforming Futures. When that's not * practical, involve only thread-safe mutable objects, as is done in the above example. * On Scala.js, by contrast, you need not worry about thread synchronization, because * in effect only one thread exists. *

* *

* Although BeforeAndAfter provides a minimal-boilerplate way to execute code before and after tests, it isn't designed to enable stackable * traits, because the order of execution would be non-obvious. If you want to factor out before and after code that is common to multiple test suites, you * should use trait BeforeAndAfterEach instead, as shown later in the next section, * composing fixtures by stacking traits. *

* *

Composing fixtures by stacking traits

* *

* In larger projects, teams often end up with several different fixtures that test classes need in different combinations, * and possibly initialized (and cleaned up) in different orders. A good way to accomplish this in ScalaTest is to factor the individual * fixtures into traits that can be composed using the stackable trait pattern. This can be done, for example, by placing * withFixture methods in several traits, each of which call super.withFixture. Here's an example in * which the StringBuilderActor and StringBufferActor fixtures used in the previous examples have been * factored out into two stackable fixture traits named Builder and Buffer: *

* *
 * package org.scalatest.examples.asyncfunsuite.composingwithasyncfixture
 * 
 * import org.scalatest._
 * import org.scalatest.SuiteMixin
 * import collection.mutable.ListBuffer
 * import scala.concurrent.Future
 * import scala.concurrent.ExecutionContext
 * 
 * // Defining actor messages
 * sealed abstract class StringOp
 * case object Clear extends StringOp
 * case class Append(value: String) extends StringOp
 * case object GetValue
 * 
 * class StringBuilderActor { // Simulating an actor
 *   private final val sb = new StringBuilder
 *   def !(op: StringOp): Unit =
 *     synchronized {
 *       op match {
 *         case Append(value) => sb.append(value)
 *         case Clear => sb.clear()
 *       }
 *     }
 *   def ?(get: GetValue.type)(implicit c: ExecutionContext): Future[String] =
 *     Future {
 *       synchronized { sb.toString }
 *     }
 * }
 * 
 * class StringBufferActor {
 *   private final val buf = ListBuffer.empty[String]
 *   def !(op: StringOp): Unit =
 *     synchronized {
 *       op match {
 *         case Append(value) => buf += value
 *         case Clear => buf.clear()
 *       }
 *     }
 *   def ?(get: GetValue.type)(implicit c: ExecutionContext): Future[List[String]] =
 *     Future {
 *       synchronized { buf.toList }
 *     }
 * }
 * 
 * trait Builder extends AsyncTestSuiteMixin { this: AsyncTestSuite =>
 * 
 *   final val builderActor = new StringBuilderActor
 * 
 *   abstract override def withFixture(test: NoArgAsyncTest) = {
 *     builderActor ! Append("ScalaTest is ")
 *     complete {
 *       super.withFixture(test) // To be stackable, must call super.withFixture
 *     } lastly {
 *       builderActor ! Clear
 *     }
 *   }
 * }
 * 
 * trait Buffer extends AsyncTestSuiteMixin { this: AsyncTestSuite =>
 * 
 *   final val bufferActor = new StringBufferActor
 * 
 *   abstract override def withFixture(test: NoArgAsyncTest) = {
 *     complete {
 *       super.withFixture(test) // To be stackable, must call super.withFixture
 *     } lastly {
 *       bufferActor ! Clear
 *     }
 *   }
 * }
 * 
 * class ExampleSuite extends AsyncFunSuite with Builder with Buffer {
 * 
 *   test("Testing should be easy") {
 *     builderActor ! Append("easy!")
 *     val futureString = builderActor ? GetValue
 *     val futureList = bufferActor ? GetValue
 *     val futurePair: Future[(String, List[String])] = futureString zip futureList
 *     futurePair map { case (str, lst) =>
 *       assert(str === "ScalaTest is easy!")
 *       assert(lst.isEmpty)
 *       bufferActor ! Append("sweet")
 *       succeed
 *     }
 *   }
 * 
 *   test("Testing should be fun") {
 *     builderActor ! Append("fun!")
 *     val futureString = builderActor ? GetValue
 *     val futureList = bufferActor ? GetValue
 *     val futurePair: Future[(String, List[String])] = futureString zip futureList
 *     futurePair map { case (str, lst) =>
 *       assert(str === "ScalaTest is fun!")
 *       assert(lst.isEmpty)
 *       bufferActor ! Append("awesome")
 *       succeed
 *     }
 *   }
 * }
 * 
* *

* By mixing in both the Builder and Buffer traits, ExampleSuite gets both fixtures, which will be * initialized before each test and cleaned up after. The order the traits are mixed together determines the order of execution. * In this case, Builder is “super” to Buffer. If you wanted Buffer to be “super” * to Builder, you need only switch the order you mix them together, like this: *

* *
 * class Example2Suite extends AsyncFunSuite with Buffer with Builder
 * 
* *

* If you only need one fixture you mix in only that trait: *

* *
 * class Example3Suite extends AsyncFunSuite with Builder
 * 
* *

* Another way to create stackable fixture traits is by extending the BeforeAndAfterEach * and/or BeforeAndAfterAll traits. * BeforeAndAfterEach has a beforeEach method that will be run before each test (like JUnit's setUp), * and an afterEach method that will be run after (like JUnit's tearDown). * Similarly, BeforeAndAfterAll has a beforeAll method that will be run before all tests, * and an afterAll method that will be run after all tests. Here's what the previously shown example would look like if it * were rewritten to use the BeforeAndAfterEach methods instead of withFixture: *

* *
 * package org.scalatest.examples.asyncfunsuite.composingbeforeandaftereach
 * 
 * import org.scalatest._
 * import org.scalatest.BeforeAndAfterEach
 * import collection.mutable.ListBuffer
 * import scala.concurrent.Future
 * import scala.concurrent.ExecutionContext
 * 
 * // Defining actor messages
 * sealed abstract class StringOp
 * case object Clear extends StringOp
 * case class Append(value: String) extends StringOp
 * case object GetValue
 * 
 * class StringBuilderActor { // Simulating an actor
 *   private final val sb = new StringBuilder
 *   def !(op: StringOp): Unit =
 *     synchronized {
 *       op match {
 *         case Append(value) => sb.append(value)
 *         case Clear => sb.clear()
 *       }
 *     }
 *   def ?(get: GetValue.type)(implicit c: ExecutionContext): Future[String] =
 *     Future {
 *       synchronized { sb.toString }
 *     }
 * }
 * 
 * class StringBufferActor {
 *   private final val buf = ListBuffer.empty[String]
 *   def !(op: StringOp): Unit =
 *     synchronized {
 *       op match {
 *         case Append(value) => buf += value
 *         case Clear => buf.clear()
 *       }
 *     }
 *   def ?(get: GetValue.type)(implicit c: ExecutionContext): Future[List[String]] =
 *     Future {
 *       synchronized { buf.toList }
 *     }
 * }
 * 
 * trait Builder extends BeforeAndAfterEach { this: Suite =>
 * 
 *   final val builderActor = new StringBuilderActor
 * 
 *   override def beforeEach() {
 *     builderActor ! Append("ScalaTest is ")
 *     super.beforeEach() // To be stackable, must call super.beforeEach
 *   }
 * 
 *   override def afterEach() {
 *     try super.afterEach() // To be stackable, must call super.afterEach
 *     finally builderActor ! Clear
 *   }
 * }
 * 
 * trait Buffer extends BeforeAndAfterEach { this: Suite =>
 * 
 *   final val bufferActor = new StringBufferActor
 * 
 *   override def afterEach() {
 *     try super.afterEach() // To be stackable, must call super.afterEach
 *     finally bufferActor ! Clear
 *   }
 * }
 * 
 * class ExampleSuite extends AsyncFunSuite with Builder with Buffer {
 * 
 *   test("Testing should be easy") {
 *     builderActor ! Append("easy!")
 *     val futureString = builderActor ? GetValue
 *     val futureList = bufferActor ? GetValue
 *     val futurePair: Future[(String, List[String])] = futureString zip futureList
 *     futurePair map { case (str, lst) =>
 *       assert(str === "ScalaTest is easy!")
 *       assert(lst.isEmpty)
 *       bufferActor ! Append("sweet")
 *       succeed
 *     }
 *   }
 * 
 *   test("Testing should be fun") {
 *     builderActor ! Append("fun!")
 *     val futureString = builderActor ? GetValue
 *     val futureList = bufferActor ? GetValue
 *     val futurePair: Future[(String, List[String])] = futureString zip futureList
 *     futurePair map { case (str, lst) =>
 *       assert(str === "ScalaTest is fun!")
 *       assert(lst.isEmpty)
 *       bufferActor ! Append("awesome")
 *       succeed
 *     }
 *   }
 * }
 * 
* *

* To get the same ordering as withFixture, place your super.beforeEach call at the end of each * beforeEach method, and the super.afterEach call at the beginning of each afterEach * method, as shown in the previous example. It is a good idea to invoke super.afterEach in a try * block and perform cleanup in a finally clause, as shown in the previous example, because this ensures the * cleanup code is performed even if super.afterEach throws an exception. *

* *

* The difference between stacking traits that extend BeforeAndAfterEach versus traits that implement withFixture is * that setup and cleanup code happens before and after the test in BeforeAndAfterEach, but at the beginning and * end of the test in withFixture. Thus if a withFixture method completes abruptly with an exception, it is * considered a failed test. By contrast, if any of the beforeEach or afterEach methods of BeforeAndAfterEach * complete abruptly, it is considered an aborted suite, which will result in a SuiteAborted event. *

* *

Shared tests

* *

* Sometimes you may want to run the same test code on different fixture objects. In other words, you may want to write tests that are "shared" * by different fixture objects. * To accomplish this in an AsyncFunSuite, you first place shared tests in * behavior functions. These behavior functions will be * invoked during the construction phase of any AsyncFunSuite that uses them, so that the tests they contain will * be registered as tests in that AsyncFunSuite. * For example, given this StackActor class: *

* *
 * package org.scalatest.examples.asyncfunsuite.sharedtests
 * 
 * import scala.collection.mutable.ListBuffer
 * import scala.concurrent.Future
 * import scala.concurrent.ExecutionContext
 * 
 * // Stack operations
 * case class Push[T](value: T)
 * sealed abstract class StackOp
 * case object Pop extends StackOp
 * case object Peek extends StackOp
 * case object Size extends StackOp
 * 
 * // Stack info
 * case class StackInfo[T](top: Option[T], size: Int, max: Int) {
 *   require(size >= 0, "size was less than zero")
 *   require(max >= size, "max was less than size")
 *   val isFull: Boolean = size == max
 *   val isEmpty: Boolean = size == 0
 * }
 * 
 * class StackActor[T](Max: Int, name: String) {
 * 
 *   private final val buf = new ListBuffer[T]
 * 
 *   def !(push: Push[T]): Unit =
 *     synchronized {
 *       if (buf.size != Max)
 *         buf.prepend(push.value)
 *       else
 *         throw new IllegalStateException("can't push onto a full stack")
 *     }
 * 
 *   def ?(op: StackOp)(implicit c: ExecutionContext): Future[StackInfo[T]] =
 *     synchronized {
 *       op match {
 *         case Pop => 
 *           if (buf.size != 0)
 *             Future { StackInfo(Some(buf.remove(0)), buf.size, Max) }
 *           else
 *             throw new IllegalStateException("can't pop an empty stack")
 *         case Peek => 
 *           if (buf.size != 0)
 *             Future { StackInfo(Some(buf(0)), buf.size, Max) }
 *           else
 *             throw new IllegalStateException("can't peek an empty stack")
 *         case Size => 
 *           Future { StackInfo(None, buf.size, Max) }
 *       }
 *     }
 * 
 *   override def toString: String = name
 * }
 * 
* *

* You may want to test the stack represented by the StackActor class in different states: empty, full, with one item, with one item less than capacity, * etc. You may find you have several tests that make sense any time the stack is non-empty. Thus you'd ideally want to run * those same tests for three stack fixture objects: a full stack, a stack with a one item, and a stack with one item less than * capacity. With shared tests, you can factor these tests out into a behavior function, into which you pass the * stack fixture to use when running the tests. So in your AsyncFunSuite for StackActor, you'd invoke the * behavior function three times, passing in each of the three stack fixtures so that the shared tests are run for all three fixtures. *

* *

* You can define a behavior function that encapsulates these shared tests inside the AsyncFunSuite that uses them. If they are shared * between different AsyncFunSuites, however, you could also define them in a separate trait that is mixed into * each AsyncFunSuite that uses them. * For example, here the nonEmptyStackActor behavior function (in this case, a * behavior method) is defined in a trait along with another * method containing shared tests for non-full stacks: *

* *
 * import org.scalatest.AsyncFunSuite
 * 
 * trait AsyncFunSuiteStackBehaviors { this: AsyncFunSuite =>
 * 
 *   def nonEmptyStackActor(createNonEmptyStackActor: => StackActor[Int],
 *         lastItemAdded: Int, name: String): Unit = {
 * 
 *     test("Size is fired at non-empty stack actor: " + name) {
 *       val stackActor = createNonEmptyStackActor
 *       val futureStackInfo = stackActor ? Size
 *       futureStackInfo map { stackInfo =>
 *         assert(!stackInfo.isEmpty)
 *       }
 *     }
 * 
 *     test("Peek is fired at non-empty stack actor: " + name) {
 *       val stackActor = createNonEmptyStackActor
 *       val futurePair: Future[(StackInfo[Int], StackInfo[Int])] = 
 *         for {
 *           beforePeek <- stackActor ? Size
 *           afterPeek <- stackActor ? Peek
 *         } yield (beforePeek, afterPeek)
 *       futurePair map { case (beforePeek, afterPeek) =>
 *         assert(afterPeek.top === Some(lastItemAdded))
 *         assert(afterPeek.size === beforePeek.size)
 *       }
 *     }
 * 
 *     test("Pop is fired at non-empty stack actor: " + name) {
 *       val stackActor = createNonEmptyStackActor
 *       val futurePair: Future[(StackInfo[Int], StackInfo[Int])] = 
 *         for {
 *           beforePop <- stackActor ? Size
 *           afterPop <- stackActor ? Pop
 *         } yield (beforePop, afterPop)
 *       futurePair map { case (beforePop, afterPop) =>
 *         assert(afterPop.top === Some(lastItemAdded))
 *         assert(afterPop.size === beforePop.size - 1)
 *       }
 *     }
 *   }
 * 
 *   def nonFullStackActor(createNonFullStackActor: => StackActor[Int], name: String): Unit = {
 * 
 *     test("non-full stack actor is not full: " + name) {
 *       val stackActor = createNonFullStackActor
 *       val futureStackInfo = stackActor ? Size
 *       futureStackInfo map { stackInfo =>
 *         assert(!stackInfo.isFull)
 *       }
 *     }
 * 
 *     test("Push is fired at non-full stack actor: " + name) {
 *       val stackActor = createNonFullStackActor
 *       val futurePair: Future[(StackInfo[Int], StackInfo[Int])] = 
 *         for {
 *           beforePush <- stackActor ? Size
 *           afterPush <- { stackActor ! Push(7); stackActor ? Peek }
 *         } yield (beforePush, afterPush)
 *       futurePair map { case (beforePush, afterPush) =>
 *         assert(afterPush.top === Some(7))
 *         assert(afterPush.size === beforePush.size + 1)
 *       }
 *     }
 *   }
 * }
 * 
* *

* Given these behavior functions, you could invoke them directly, but AsyncFunSuite offers a DSL for the purpose, * which looks like this: *

* *
 * testsFor(nonEmptyStackActor(almostEmptyStackActor, LastValuePushed, almostEmptyStackActorName))
 * testsFor(nonFullStackActor(almostEmptyStackActor, almostEmptyStackActorName))
 * 
* *

* Here's an example: *

* *
 * class StackSuite extends AsyncFunSuite with AsyncFunSuiteStackBehaviors {
 * 
 *   val Max = 10
 *   val LastValuePushed = Max - 1
 * 
 *   // Stack fixture creation methods
 *   val emptyStackActorName = "empty stack actor"
 *   def emptyStackActor = new StackActor[Int](Max, emptyStackActorName )
 * 
 *   val fullStackActorName = "full stack actor"
 *   def fullStackActor = {
 *     val stackActor = new StackActor[Int](Max, fullStackActorName )
 *     for (i <- 0 until Max)
 *       stackActor ! Push(i)
 *     stackActor
 *   }
 * 
 *   val almostEmptyStackActorName = "almost empty stack actor"
 *   def almostEmptyStackActor = {
 *     val stackActor = new StackActor[Int](Max, almostEmptyStackActorName )
 *     stackActor ! Push(LastValuePushed)
 *     stackActor
 *   }
 * 
 *   val almostFullStackActorName = "almost full stack actor"
 *   def almostFullStackActor = {
 *     val stackActor = new StackActor[Int](Max, almostFullStackActorName)
 *     for (i <- 1 to LastValuePushed)
 *       stackActor ! Push(i)
 *     stackActor
 *   }
 * 
 *   test("an empty stack actor is empty") {
 *     val stackActor = emptyStackActor
 *     val futureStackInfo = stackActor ? Size
 *     futureStackInfo map { stackInfo =>
 *       assert(stackInfo.isEmpty)
 *     }
 *   }
 * 
 *   test("Peek is fired at an empty stack actor") {
 *     recoverToSucceededIf[IllegalStateException] {
 *       emptyStackActor ? Peek
 *     }
 *   }
 * 
 *   test("Pop is fired at an empty stack actor") {
 *     recoverToSucceededIf[IllegalStateException] {
 *       emptyStackActor ? Pop
 *     }
 *   }
 * 
 *   testsFor(nonEmptyStackActor(almostEmptyStackActor, LastValuePushed, almostEmptyStackActorName))
 *   testsFor(nonFullStackActor(almostEmptyStackActor, almostEmptyStackActorName))
 * 
 *   testsFor(nonEmptyStackActor(almostFullStackActor, LastValuePushed, almostFullStackActorName))
 *   testsFor(nonFullStackActor(almostFullStackActor, almostFullStackActorName))
 * 
 *   test("a full stack actor is full") {
 *     val stackActor = fullStackActor
 *     val futureStackInfo = stackActor ? Size
 *     futureStackInfo map { stackInfo =>
 *       assert(stackInfo.isFull)
 *     }
 *   }
 * 
 *   testsFor(nonEmptyStackActor(fullStackActor, LastValuePushed, fullStackActorName))
 * 
 *   test("Push is fired at a full stack actor") {
 *     val stackActor = fullStackActor
 *     assertThrows[IllegalStateException] {
 *       stackActor ! Push(10)
 *     }
 *   }
 * }
 * 
* *

* If you load these classes into the Scala interpreter (with scalatest's JAR file on the class path), and execute it, * you'll see: *

* *
 * scala> org.scalatest.run(new StackSuite)
 * StackSuite:
 * StackSuite:
 * - an empty stack actor is empty
 * - Peek is fired at an empty stack actor
 * - Pop is fired at an empty stack actor
 * - Size is fired at non-empty stack actor: almost empty stack actor
 * - Peek is fired at non-empty stack actor: almost empty stack actor
 * - Pop is fired at non-empty stack actor: almost empty stack actor
 * - non-full stack actor is not full: almost empty stack actor
 * - Push is fired at non-full stack actor: almost empty stack actor
 * - Size is fired at non-empty stack actor: almost full stack actor
 * - Peek is fired at non-empty stack actor: almost full stack actor
 * - Pop is fired at non-empty stack actor: almost full stack actor
 * - non-full stack actor is not full: almost full stack actor
 * - Push is fired at non-full stack actor: almost full stack actor
 * - a full stack actor is full
 * - Size is fired at non-empty stack actor: full stack actor
 * - Peek is fired at non-empty stack actor: full stack actor
 * - Pop is fired at non-empty stack actor: full stack actor
 * - Push is fired at a full stack actor
 * 
* *

* One thing to keep in mind when using shared tests is that in ScalaTest, each test in a suite must have a unique name. * If you register the same tests repeatedly in the same suite, one problem you may encounter is an exception at runtime * complaining that multiple tests are being registered with the same test name. * In a AsyncFunSuite there is no nesting construct analogous to * AsyncFunSpec's describe clause. * Therefore, you need to do a bit of * extra work to ensure that the test names are unique. If a duplicate test name problem shows up in an * AsyncFunSuite, you'll need to pass in a prefix or suffix string to add to each test name. You can call * toString on the shared fixture object, or pass this string * the same way you pass any other data needed by the shared tests. * This is the approach taken by the previous AsyncFunSuiteStackBehaviors example. *

* *

* Given this AsyncFunSuiteStackBehaviors trait, calling it with the stackWithOneItem fixture, like this: *

* *
 * testsFor(nonEmptyStackActor(almostFullStackActor, LastValuePushed, almostFullStackActorName))
 * 
* *

* yields test names: *

* *
    *
  • Size is fired at non-empty stack actor: almost empty stack actor
  • *
  • Peek is fired at non-empty stack actor: almost empty stack actor
  • *
  • Pop is fired at non-empty stack actor: almost empty stack actor
  • *
* *

* Whereas calling it with the stackWithOneItemLessThanCapacity fixture, like this: *

* *
 * testsFor(nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed))
 * 
* *

* yields different test names: *

* *
    *
  • Size is fired at non-empty stack actor: almost full stack actor
  • *
  • Peek is fired at non-empty stack actor: almost full stack actor
  • *
  • Pop is fired at non-empty stack actor: almost full stack actor
  • *
*/ abstract class AsyncFunSuite extends AsyncFunSuiteLike { /** * Returns a user friendly string for this suite, composed of the * simple name of the class (possibly simplified further by removing dollar signs if added by the Scala interpeter) and, if this suite * contains nested suites, the result of invoking toString on each * of the nested suites, separated by commas and surrounded by parentheses. * * @return a user-friendly string for this suite */ override def toString: String = Suite.suiteToString(None, this) } /* May take from this later: In an AsyncFunSuite, threads that transform and perform callbacks for Futures are taken from the implicit execution context. On Scala.js, you need not worry about thread synchronization, because JavaScript is essentially single-threaded. On the JVM, however, multiple transformations and callbacks of Futures that operate on mutable state will need to be synchronized, because they may be performed by different thrads. The best way to avoid this issue is to avoid mutable state in the first place-i.e., to use a functional style. Use Futures only to transform immutable objects without any side effects. When that is not practical, one option on the JVM is to block, either using scala.concurrent.Await or the methods of ScalaFutures. Blocking will also allow you to use a synchronous style, such as FunSuite, which doesn't take threads fron an execution context. Synchronous styles are designed so that you need not worry about synchronizing access to mutable state shared between tests, because only one thread executes each test. Even if you ix in PTE, you need not synchronize access to instance variables because each test is executed in its own instance of the test class, so each test has its own copy of the instance variables. On Scala.js, you can't block, so using Await or ScalaFutures will not work if you Futures are truly asynchronous (involve calling APIs that work outside of the JS thread) On Scala.js, therefore, you must use async style tests to test asynchrounous code, but you need not worry about synchronoization. ON the JVM, you can block, so you have the option to use synchronous style tests to test asynchronous code. If you choose to write async-style tests on the JVM, you must ensure that the objects you manipulate through Futures are thread-safe (and the easiest way to do that is make them immutable). */




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