Describe a “subject” being specified and tested by the passed function value.
Describe a “subject” being specified and tested by the passed function value. The
passed function value may contain more describers (defined with describe
) and/or tests
(defined with it
). This trait's implementation of this method will register the
description string and immediately invoke the passed function.
Register a test with the given spec text, optional tags, and test function value that takes no arguments.
Register a test with the given spec text, optional tags, and test function value that takes no arguments. An invocation of this method is called an “example.”
This method will register the test for later execution via an invocation of one of the execute
methods. The name of the test will be a concatenation of the text of all surrounding describers,
from outside in, and the passed spec text, with one space placed between each item. (See the documenation
for testNames
for an example.) The resulting test name must not have been registered previously on
this AsyncFeatureSpec
instance.
the specification text, which will be combined with the descText of any surrounding describers to form the test name
the optional list of tags for this test
the test function
if a test with the same name has been registered previously
NullArgumentExceptionif specText
or any passed test tag is null
if invoked after run
has been invoked on this suite
Registers shared scenarios.
Registers shared scenarios.
This method enables the following syntax for shared scenarios in a AsyncFeatureSpec
:
ScenariosFor(nonEmptyStack(lastValuePushed))
This method just provides syntax sugar intended to make the intent of the code clearer.
Because the parameter passed to it is
type Unit
, the expression will be evaluated before being passed, which
is sufficient to register the shared scenarios. For examples of shared scenarios, see the
Shared scenarios section in the main documentation for this trait.
Returns an Alerter
that during test execution will forward strings (and other objects) passed to its
apply
method to the current reporter.
Returns an Alerter
that during test execution will forward strings (and other objects) passed to its
apply
method to the current reporter. If invoked in a constructor, it
will register the passed string for forwarding later during test execution. If invoked while this
FunSpec
is being executed, such as from inside a test function, it will forward the information to
the current reporter immediately. If invoked at any other time, it will
print to the standard output. This method can be called safely by any thread.
Register a test to ignore, which has the given spec text, optional tags, and test function value that takes no arguments.
Register a test to ignore, which has the given spec text, optional tags, and test function value that takes no arguments.
This method will register the test for later ignoring via an invocation of one of the execute
methods. This method exists to make it easy to ignore an existing test by changing the call to it
to ignore
without deleting or commenting out the actual test code. The test will not be executed, but a
report will be sent that indicates the test was ignored. The name of the test will be a concatenation of the text of all surrounding describers,
from outside in, and the passed spec text, with one space placed between each item. (See the documenation
for testNames
for an example.) The resulting test name must not have been registered previously on
this AsyncFeatureSpec
instance.
the specification text, which will be combined with the descText of any surrounding describers to form the test name
the optional list of tags for this test
the test function
if a test with the same name has been registered previously
NullArgumentExceptionif specText
or any passed test tag is null
if invoked after run
has been invoked on this suite
Returns an Informer
that during test execution will forward strings passed to its
apply
method to the current reporter.
Returns an Informer
that during test execution will forward strings passed to its
apply
method to the current reporter. If invoked in a constructor, it
will register the passed string for forwarding later during test execution. If invoked from inside a scope,
it will forward the information to the current reporter immediately. If invoked from inside a test function,
it will record the information and forward it to the current reporter only after the test completed, as recordedEvents
of the test completed event, such as TestSucceeded
. If invoked at any other time, it will print to the standard output.
This method can be called safely by any thread.
Returns a Documenter
that during test execution will forward strings passed to its
apply
method to the current reporter.
Returns a Documenter
that during test execution will forward strings passed to its
apply
method to the current reporter. If invoked in a constructor, it
will register the passed string for forwarding later during test execution. If invoked from inside a scope,
it will forward the information to the current reporter immediately. If invoked from inside a test function,
it will record the information and forward it to the current reporter only after the test completed, as recordedEvents
of the test completed event, such as TestSucceeded
. If invoked at any other time, it will print to the standard output.
This method can be called safely by any thread.
Returns a Notifier
that during test execution will forward strings (and other objects) passed to its
apply
method to the current reporter.
Returns a Notifier
that during test execution will forward strings (and other objects) passed to its
apply
method to the current reporter. If invoked in a constructor, it
will register the passed string for forwarding later during test execution. If invoked while this
FunSpec
is being executed, such as from inside a test function, it will forward the information to
the current reporter immediately. If invoked at any other time, it will
print to the standard output. This method can be called safely by any thread.
Run a test.
Run a test. This trait's implementation runs the test registered with the name specified by
testName
. Each test's name is a concatenation of the text of all describers surrounding a test,
from outside in, and the test's spec text, with one space placed between each item. (See the documenation
for testNames
for an example.)
the name of one test to execute.
the Args
for this run
a Status
object that indicates when the test started by this method has completed, and whether or not it failed .
if any of testName
, reporter
, stopper
, or configMap
is null
.
Run zero to many of this AsyncFeatureSpec
's tests.
Run zero to many of this AsyncFeatureSpec
's tests.
This method takes a testName
parameter that optionally specifies a test to invoke.
If testName
is Some
, this trait's implementation of this method
invokes runTest
on this object, passing in:
testName
- the String
value of the testName
Option
passed
to this methodreporter
- the Reporter
passed to this method, or one that wraps and delegates to itstopper
- the Stopper
passed to this method, or one that wraps and delegates to itconfigMap
- the configMap
passed to this method, or one that wraps and delegates to itThis method takes a Set
of tag names that should be included (tagsToInclude
), and a Set
that should be excluded (tagsToExclude
), when deciding which of this Suite
's tests to execute.
If tagsToInclude
is empty, all tests will be executed
except those those belonging to tags listed in the tagsToExclude
Set
. If tagsToInclude
is non-empty, only tests
belonging to tags mentioned in tagsToInclude
, and not mentioned in tagsToExclude
will be executed. However, if testName
is Some
, tagsToInclude
and tagsToExclude
are essentially ignored.
Only if testName
is None
will tagsToInclude
and tagsToExclude
be consulted to
determine which of the tests named in the testNames
Set
should be run. For more information on trait tags, see the main documentation for this trait.
If testName
is None
, this trait's implementation of this method
invokes testNames
on this Suite
to get a Set
of names of tests to potentially execute.
(A testNames
value of None
essentially acts as a wildcard that means all tests in
this Suite
that are selected by tagsToInclude
and tagsToExclude
should be executed.)
For each test in the testName
Set
, in the order
they appear in the iterator obtained by invoking the elements
method on the Set
, this trait's implementation
of this method checks whether the test should be run based on the tagsToInclude
and tagsToExclude
Set
s.
If so, this implementation invokes runTest
, passing in:
testName
- the String
name of the test to run (which will be one of the names in the testNames
Set
)reporter
- the Reporter
passed to this method, or one that wraps and delegates to itstopper
- the Stopper
passed to this method, or one that wraps and delegates to itconfigMap
- the configMap
passed to this method, or one that wraps and delegates to itan optional name of one test to run. If None
, all relevant tests should be run.
I.e., None
acts like a wildcard that means run all relevant tests in this Suite
.
the Args
for this run
a Status
object that indicates when all tests started by this method have completed, and whether or not a failure occurred.
if testName
is defined, but no test with the specified test name
exists in this Suite
if any of the passed parameters is null
.
A Map
whose keys are String
names of tagged tests and whose associated values are
the Set
of tag names for the test.
A Map
whose keys are String
names of tagged tests and whose associated values are
the Set
of tag names for the test. If this AsyncFeatureSpec
contains no tags, this method returns an empty Map
.
This trait's implementation returns tags that were passed as strings contained in Tag
objects passed to
methods scenario
and ignore
.
In addition, this trait's implementation will also auto-tag tests with class level annotations.
For example, if you annotate @Ignore
at the class level, all test methods in the class will be auto-annotated with
org.scalatest.Ignore
.
An immutable Set
of test names.
An immutable Set
of test names. If this AsyncFeatureSpec
contains no tests, this method returns an
empty Set
.
This trait's implementation of this method will return a set that contains the names of all registered tests. The set's
iterator will return those names in the order in which the tests were registered. Each test's name is composed
of the concatenation of the text of each surrounding describer, in order from outside in, and the text of the
example itself, with all components separated by a space. For example, consider this AsyncFeatureSpec
:
import org.scalatest.featurespec.AsyncFeatureSpec class StackSpec extends AsyncFeatureSpec { Feature("A Stack") { Scenario("(when not empty) must allow me to pop") { succeed } Scenario("(when not full) must allow me to push") { succeed } } }
Invoking testNames
on this AsyncFeatureSpec
will yield a set that contains the following
two test name strings:
"A Stack (when not empty) must allow me to pop" "A Stack (when not full) must allow me to push"
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.
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.
a user-friendly string for this suite
(Since version 3.1.0) The conversionCheckedConstraint method has been deprecated and will be removed in a future version of ScalaTest. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.
(Since version 3.1.0) The convertEquivalenceToAToBConversionConstraint method has been deprecated and will be removed in a future version of ScalaTest. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.
(Since version 3.1.0) The convertEquivalenceToBToAConversionConstraint method has been deprecated and will be removed in a future version of ScalaTest. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.
The feature
(starting with lowercase 'f') method has been deprecated and will be removed in a future version of ScalaTest. Please use Feature
(starting with an uppercase 'F') instead.
The feature
(starting with lowercase 'f') method has been deprecated and will be removed in a future version of ScalaTest. Please use Feature
(starting with an uppercase 'F') instead.
This method has been renamed for consistency with ScalaTest's Given
, When
, and Then
methods, which were changed to uppper case
when Scala deprecated then
as an identifier, and Cucumber, one of the main original inspirations for FeatureSpec
.
This can be rewritten automatically with autofix: https://github.com/scalatest/autofix/tree/master/3.1.x.
(Since version 3.1.0) The feature (starting with lowercase 'f') method has been deprecated and will be removed in a future version of ScalaTest. Please use Feature (starting with an uppercase 'F') instead. This can be rewritten automatically with autofix: https://github.com/scalatest/autofix/tree/master/3.1.x
(Since version 3.1.0) The lowPriorityConversionCheckedConstraint method has been deprecated and will be removed in a future version of ScalaTest. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.
The scenario
(starting with lowercase 's') method has been deprecated and will be removed in a future version of ScalaTest. Please use Scenario
(starting with an uppercase 'S') instead.
The scenario
(starting with lowercase 's') method has been deprecated and will be removed in a future version of ScalaTest. Please use Scenario
(starting with an uppercase 'S') instead.
This method has been renamed for consistency with ScalaTest's Given
, When
, and Then
methods, which were changed to uppper case
when Scala deprecated then
as an identifier, and Cucumber, one of the main original inspirations for FeatureSpec
.
This can be rewritten automatically with autofix: https://github.com/scalatest/autofix/tree/master/3.1.x.
(Since version 3.1.0) The scenario (starting with lowercase 's') method has been deprecated and will be removed in a future version of ScalaTest. Please use Scenario (starting with an uppercase 'S') instead. This can be rewritten automatically with autofix: https://github.com/scalatest/autofix/tree/master/3.1.x
The scenariosFor
(starting with lowercase 's') method has been deprecated and will be removed in a future version of ScalaTest. Please use ScenariosFor
(starting with an uppercase 'S') instead.
The scenariosFor
(starting with lowercase 's') method has been deprecated and will be removed in a future version of ScalaTest. Please use ScenariosFor
(starting with an uppercase 'S') instead.
This method has been renamed for consistency with ScalaTest's Given
, When
, and Then
methods, which were changed to uppper case
when Scala deprecated then
as an identifier, and Cucumber, one of the main original inspirations for FeatureSpec
.
This can be rewritten automatically with autofix: https://github.com/scalatest/autofix/tree/master/3.1.x.
(Since version 3.1.0) The scenariosFor (starting with lowercase 's') method has been deprecated and will be removed in a future version of ScalaTest. Please use ScenariosFor (starting with an uppercase 'S') instead. This can be rewritten automatically with autofix: https://github.com/scalatest/autofix/tree/master/3.1.x
The styleName
lifecycle method has been deprecated and will be removed in a future version of ScalaTest.
The styleName
lifecycle method has been deprecated and will be removed in a future version of ScalaTest.
This method was used to support the chosen styles feature, which was deactivated in 3.1.0. The internal modularization of ScalaTest in 3.2.0
will replace chosen styles as the tool to encourage consistency across a project. We do not plan a replacement for styleName
.
(Since version 3.1.0) The styleName lifecycle method has been deprecated and will be removed in a future version of ScalaTest with no replacement.
Enables testing of asynchronous code without blocking, using a style consistent with traditional
AnyFeatureSpec
tests.AsyncFeatureSpec
is intended to enable users ofAnyFeatureSpec
to write non-blocking asynchronous tests that are consistent with their traditionalAnyFeatureSpec
tests. Note:AsyncFeatureSpec
is intended for use in special situations where non-blocking asynchronous testing is needed, with classAnyFeatureSpec
used for general needs.Given a
Future
returned by the code you are testing, you need not block until theFuture
completes before performing assertions against its value. You can instead map those assertions onto theFuture
and return the resultingFuture[Assertion]
to ScalaTest. The test will complete asynchronously, when theFuture[Assertion]
completes.Although not required,
AsyncFeatureSpec
is often used together withGivenWhenThen
to express acceptance requirements in more detail. Here's an exampleAsyncFeatureSpec
:Note: for more information on the calls to
Given
,When
, andThen
, see the documentation for traitGivenWhenThen
and theInformers
section below.An
AsyncFeatureSpec
contains feature clauses and scenarios. You define a feature clause withfeature
, and a scenario withscenario
. Bothfeature
andscenario
are methods, defined inAsyncFeatureSpec
, which will be invoked by the primary constructor ofTVSetActorSpec
. A feature clause describes a feature of the subject (class or other entity) you are specifying and testing. In the previous example, the subject under specification and test is a TV set. The feature being specified and tested is the behavior of a TV set when its power button is pressed. With each scenario you provide a string (the spec text) that specifies the behavior of the subject for one scenario in which the feature may be used, and a block of code that tests that behavior. You place the spec text between the parentheses, followed by the test code between curly braces. The test code will be wrapped up as a function passed as a by-name parameter toscenario
, which will register the test for later execution. The result type of the by-name in anAsyncFeatureSpec
must beFuture[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, isFuture[Assertion]
. When anAsyncFeatureSpec
is constructed, any test that results inAssertion
will be implicitly converted toFuture[Assertion]
and registered. The implicit conversion is fromAssertion
toFuture[Assertion]
only, so you must end synchronous tests in some ScalaTest assertion or matcher expression. If a test would not otherwise end in typeAssertion
, you can placesucceed
at the end of the test.succeed
, a field in traitAssertions
, returns theSucceeded
singleton:Thus placing
succeed
at the end of a test body will satisfy the type checker.An
AsyncFeatureSpec
's lifecycle has two phases: the registration phase and the ready phase. It starts in registration phase and enters ready phase the first timerun
is called on it. It then remains in ready phase for the remainder of its lifetime.Scenarios can only be registered with the
scenario
method while theAsyncFeatureSpec
is in its registration phase. Any attempt to register a scenario after theAsyncFeatureSpec
has entered its ready phase, i.e., afterrun
has been invoked on theAsyncFeatureSpec
, will be met with a thrownTestRegistrationClosedException
. The recommended style of usingAsyncFeatureSpec
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 aTestRegistrationClosedException
.Each scenario represents one test. The name of the test is the spec text passed to the
scenario
method. The feature name does not appear as part of the test name. In aAsyncFeatureSpec
, therefore, you must take care to ensure that each test has a unique name (in other words, that eachscenario
has unique spec text).When you run a
AsyncFeatureSpec
, it will sendFormatter
s in the events it sends to theReporter
. ScalaTest's built-in reporters will report these events in such a way that the output is easy to read as an informal specification of the subject being tested. For example, were you to runTVSetSpec
from within the Scala interpreter:You would see:
TVSetActorSpec: As a TV set owner I want to be able to turn the TV on and off So I can watch TV when I want And save energy when I'm not watching TV Feature: TV power button Scenario: User presses power button when TV is off Given a TV set that is switched off When the power button is pressed Then the TV should switch on Scenario: User presses power button when TV is on Given a TV set that is switched on When the power button is pressed Then the TV should switch off
Or, to run just the “
Feature: TV power button Scenario: User presses power button when TV is on
” method, you could pass that test's name, or any unique substring of the name, such as"TV is on"
. Here's an example:scala> org.scalatest.run(new TVSetActorSpec, "TV is on") TVSetActorSpec: As a TV set owner I want to be able to turn the TV on and off So I can watch TV when I want And save energy when I'm not watching TV Feature: TV power button Scenario: User presses power button when TV is on Given a TV set that is switched on When the power button is pressed Then the TV should switch off
Asynchronous execution model
AsyncFeatureSpec
extendsAsyncTestSuite
, which provides an implicitscala.concurrent.ExecutionContext
namedexecutionContext
. This execution context is used byAsyncFeatureSpec
to transform theFuture[Assertion]
s returned by each test into theFutureOutcome
returned by thetest
function passed towithFixture
. ThisExecutionContext
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 theFutureOutcome
returned from thetest
function. Other tasks that will be queued are any transformations of, or callbacks registered on,Future
s that occur in your test body, including any assertions you map ontoFuture
s. 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 ofFuture
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]
. ThisFuture[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 theFuture[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
AnyFeatureSpec
withScalaFutures
instead. Alternatively, you could override theexecutionContext
and use a traditionalExecutionContext
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 therunNow
execution context on Scala.js instead of the defaultqueue
, you would write: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:
Serial and parallel test execution
By default (unless you mix in
ParallelTestExecution
), tests in anAsyncFeatureSpec
will be executed one after another, i.e., serially. This is true whether those tests returnAssertion
orFuture[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
AsyncFeatureSpec
to be executed in parallel, you must mix inParallelTestExecution
and enable parallel execution of tests in your build. You enable parallel execution inRunner
with the-P
command line flag. In the ScalaTest Maven Plugin, setparallel
totrue
. Insbt
, parallel execution is the default, but to be explicit you can write: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 theDistributor
, and allowed to complete in parallel, using threads from theexecutionContext
. If you are using ScalaTest's serial execution context, the JVM default, asynchronous tests will run in parallel very much like traditional (such asAnyFeatureSpec
) tests run in parallel: 1) BecauseParallelTestExecution
extendsOneInstancePerTest
, 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 ofFuture
s 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 invokedrun
, 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 theexecutionContext
. 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 inParallelTestExecution
is executed: the tests will run sequentially. If you use an execution context backed by a thread-pool, such asglobal
, 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
andrecoverToExceptionIf
methods of traitRecoverMethods
. Because this trait is mixed into supertraitAsyncTestSuite
, both of these methods are available by default in anAsyncFeatureSpec
.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
:The
recoverToSucceededIf
method performs a job similar toassertThrows
, except in the context of a future. It transforms aFuture
of any type into aFuture[Assertion]
that succeeds only if the original future fails with the specified exception. Here's an example in the REPL:Otherwise it fails with an error message similar to those given by
assertThrows
:The
recoverToExceptionIf
method differs from therecoverToSucceededIf
in its behavior when the assertion succeeds:recoverToSucceededIf
yields aFuture[Assertion]
, whereasrecoverToExceptionIf
yields aFuture[T]
, whereT
is the expected exception type.In other words,
recoverToExpectionIf
is tointercept
asrecovertToSucceededIf
is toassertThrows
. 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 showingrecoverToExceptionIf
in the REPL: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,
AsyncFeatureSpec
provides registration methods that start withignore
instead ofscenario
. Here's an example:If you run class
AddSpec
with:It will run only the second test and report that the first test was ignored:
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: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
AddSpec
in the above example with the@Ignore
tag annotation means that both tests in the class will be ignored. If you run the aboveAddSpec
in the Scala interpreter, you'll see: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
it
toignore
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
AsyncFeatureSpec
'srun
method is aReporter
, 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 theReporter
as the suite runs. Most often the default reporting done byAsyncFeatureSpec
's methods will be sufficient, but occasionally you may wish to provide custom information to theReporter
from a test. For this purpose, anInformer
that will forward information to the currentReporter
is provided via theinfo
parameterless method. You can pass the extra information to theInformer
via itsapply
method. TheInformer
will then pass the information to theReporter
via anInfoProvided
event.One use case for the
Informer
is to pass more information about a scenario to the reporter. For example, theGivenWhenThen
trait provides methods that use the implicitinfo
provided byAsyncFeatureSpec
to pass such information to the reporter. You can see this in action in the initial example of this trait's documentation.Documenters
AsyncFeatureSpec
also provides amarkup
method that returns aDocumenter
, which allows you to send to theReporter
text formatted in Markdown syntax. You can pass the extra information to theDocumenter
via itsapply
method. TheDocumenter
will then pass the information to theReporter
via anMarkupProvided
event.Here's an example
FlatSpec
that usesmarkup
: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 aboveSetSpec
would look like in the HTML reporter:Notifiers and alerters
ScalaTest records text passed to
info
andmarkup
during tests, and sends the recorded text in therecordedEvents
field of test completion events likeTestSucceeded
andTestFailed
. This allows string reporters (like the standard out reporter) to showinfo
andmarkup
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 theinfo
andmarkup
text in red. If a test succeeds, string reporters will show theinfo
andmarkup
text in green. While this approach helps the readability of reports, it means that you can't useinfo
to get status updates from long running tests.To get immediate (i.e., non-recorded) notifications from tests, you can use
note
(aNotifier
) andalert
(anAlerter
). Here's an example showing the differences:Because
note
andalert
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: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
andmarkup
for text that should form part of the specification output. Usenote
andalert
to send status notifications. (Because the HTML reporter is intended to produce a readable, printable specification,info
andmarkup
text will appear in the HTML report, butnote
andalert
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 withTestPendingException
.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 withTestPendingException
, 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:(Note: "
(pending)
" is the body of the test. Thus the test contains just one statement, an invocation of thepending
method, which throwsTestPendingException
.) If you run this version ofAddSpec
with:It will run both tests, but report that first test is pending. You'll see:
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 thepending
method does). Thus the body of pending tests are executed up until they throwTestPendingException
.Tagging tests
An
AsyncFeatureSpec
's tests may be classified into groups by tagging them with string names. As with any suite, when executing anAsyncFeatureSpec
, groups of tests can optionally be included and/or excluded. To tag anAsyncFeatureSpec
's tests, you pass objects that extend classorg.scalatest.Tag
to methods that register tests. ClassTag
takes one parameter, a string name. If you have created tag annotation interfaces as described in theTag
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 theTag
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 forAsyncFeatureSpec
s like this:Given these definitions, you could place
AsyncFeatureSpec
tests into groups with tags like this:This code marks both tests with the
org.scalatest.tags.Slow
tag, and the second test with thecom.mycompany.tags.DbTest
tag.The
run
method takes aFilter
, whose constructor takes an optionalSet[String]
calledtagsToInclude
and aSet[String]
calledtagsToExclude
. IftagsToInclude
isNone
, all tests will be run except those those belonging to tags listed in thetagsToExclude
Set
. IftagsToInclude
is defined, only tests belonging to tags mentioned in thetagsToInclude
set, and not mentioned intagsToExclude
, 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 anAsyncFeatureSpec
in one stroke by annotating the class. For more information and examples, see the documentation for classTag
. 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:
withFixture
Each technique is geared towards helping you reduce code duplication without introducing instance
var
s, 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:
withFixture
when most or all tests need the same fixture.withFixture(NoArgAsyncTest)
withFixture(OneArgAsyncTest)
instead)withFixture(OneArgAsyncTest)
BeforeAndAfter
BeforeAndAfterEach
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:
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 traitAsyncTestSuite
, a supertrait ofAsyncFeatureSpec
.Trait
AsyncFeatureSpec
'srunTest
method passes a no-arg async test function towithFixture(NoArgAsyncTest)
. It iswithFixture
's responsibility to invoke that test function. The default implementation ofwithFixture
simply invokes the function and returns the result, like this: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 thecomplete
-lastly
syntax, defined in supertraitCompleteLastly
. Thecomplete
-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 thesuper
implementation ofwithFixture
, 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:If you have no cleanup to perform, you can write
withFixture
like this instead: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 ofFuture
's registration methods:onComplete
,onSuccess
, oronFailure
. Note that if a test fails, that will be treated as ascala.util.Success(org.scalatest.Failed)
. So if you want to perform an action if a test fails, for example, you'd register the callback usingonSuccess
.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:Running this version of
ExampleSpec
in the interpreter in a directory with two files,hello.txt
andworld.txt
would give the following output:Note that the
NoArgAsyncTest
passed towithFixture
, in addition to anapply
method that executes the test, also includes the test name and the config map passed torunTest
. Thus you can also use the test name and configuration objects in yourwithFixture
implementation.Lastly, if you want to transform the outcome in some way in
withFixture
, you'll need to use either themap
ortransform
methods ofFuture
, like this:Note that a
NoArgAsyncTest
'sapply
method will return ascala.util.Failure
only if the test completes abruptly with a "test-fatal" exception (such asOutOfMemoryError
) that should cause the suite to abort rather than the test to fail. Thus usually you would usemap
to transform future outcomes, nottransform
, so that such test-fatal exceptions pass through unchanged. The suite will abort asynchronously with any exception returned fromNoArgAsyncTest
's apply method in ascala.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
.)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
FixtureAsyncTestSuite
and overridingwithFixture(OneArgAsyncTest)
. Each test in aFixtureAsyncTestSuite
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 specifyingFixtureParam
, and implement awithFixture
method that takes aOneArgAsyncTest
. ThiswithFixture
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 letwithFixture(NoArgAsyncTest)
invoke the test function instead of invoking the test function directly. To do so, you'll need to convert theOneArgAsyncTest
to aNoArgAsyncTest
. You can do that by passing the fixture object to thetoNoArgAsyncTest
method ofOneArgAsyncTest
. In other words, instead of writing “test(theFixture)
”, you'd delegate responsibility for invoking the test function to thewithFixture(NoArgAsyncTest)
method of the same instance by writing:Here's a complete example:
In this example, the tests required one fixture object, a
StringActor
. If your tests need multiple fixture objects, you can simply define theFixtureParam
type to be a tuple containing the objects or, alternatively, a case class containing the objects. For more information on thewithFixture(OneArgAsyncTest)
technique, see the documentation forFixtureAsyncFeatureSpec
.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 withbefore
and/or after each test each test withafter
, like this:Note that the only way
before
andafter
code can communicate with test code is via some side-effecting mechanism, commonly by reassigning instancevar
s or by changing the state of mutable objects held from instanceval
s (as in this example). If using instancevar
s or mutable objects held from instanceval
s 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 ofFuture
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 transformingFuture
s. 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 traitBeforeAndAfterEach
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 callsuper.withFixture
. Here's an example in which theStringBuilderActor
andStringBufferActor
fixtures used in the previous examples have been factored out into two stackable fixture traits namedBuilder
andBuffer
:By mixing in both the
Builder
andBuffer
traits,ExampleSpec
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” toBuffer
. If you wantedBuffer
to be “super” toBuilder
, you need only switch the order you mix them together, like this:If you only need one fixture you mix in only that trait:
Another way to create stackable fixture traits is by extending the
BeforeAndAfterEach
and/orBeforeAndAfterAll
traits.BeforeAndAfterEach
has abeforeEach
method that will be run before each test (like JUnit'ssetUp
), and anafterEach
method that will be run after (like JUnit'stearDown
). Similarly,BeforeAndAfterAll
has abeforeAll
method that will be run before all tests, and anafterAll
method that will be run after all tests. Here's what the previously shown example would look like if it were rewritten to use theBeforeAndAfterEach
methods instead ofwithFixture
:To get the same ordering as
withFixture
, place yoursuper.beforeEach
call at the end of eachbeforeEach
method, and thesuper.afterEach
call at the beginning of eachafterEach
method, as shown in the previous example. It is a good idea to invokesuper.afterEach
in atry
block and perform cleanup in afinally
clause, as shown in the previous example, because this ensures the cleanup code is performed even ifsuper.afterEach
throws an exception.The difference between stacking traits that extend
BeforeAndAfterEach
versus traits that implementwithFixture
is that setup and cleanup code happens before and after the test inBeforeAndAfterEach
, but at the beginning and end of the test inwithFixture
. Thus if awithFixture
method completes abruptly with an exception, it is considered a failed test. By contrast, if any of thebeforeEach
orafterEach
methods ofBeforeAndAfterEach
complete abruptly, it is considered an aborted suite, which will result in aSuiteAborted
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
AsyncFeatureSpec
, you first place shared tests in behavior functions. These behavior functions will be invoked during the construction phase of anyAsyncFeatureSpec
that uses them, so that the tests they contain will be registered as tests in thatAsyncFeatureSpec
. For example, given thisStackActor
class: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 yourAsyncFeatureSpec
forStackActor
, 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
AsyncFeatureSpec
that uses them. If they are shared between differentAsyncFeatureSpec
s, however, you could also define them in a separate trait that is mixed into eachAsyncFeatureSpec
that uses them. For example, here thenonEmptyStackActor
behavior function (in this case, a behavior method) is defined in a trait along with another method containing shared tests for non-full stacks:Given these behavior functions, you could invoke them directly, but
AsyncFeatureSpec
offers a DSL for the purpose, which looks like this:Here's an example:
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 StackSpec) StackSpec: Feature: A Stack actor - Scenario: Size is fired at empty stack actor - Scenario: Peek is fired at empty stack actor - Scenario: Pop is fired at empty stack actor - Scenario: Size is fired at non-empty stack actor: almost empty stack actor - Scenario: Peek is fired at non-empty stack actor: almost empty stack actor - Scenario: Pop is fired at non-empty stack actor: almost empty stack actor - Scenario: Size is fired at non-full stack actor: almost empty stack actor - Scenario: Push is fired at non-full stack actor: almost empty stack actor - Scenario: Size is fired at non-empty stack actor: almost full stack actor - Scenario: Peek is fired at non-empty stack actor: almost full stack actor - Scenario: Pop is fired at non-empty stack actor: almost full stack actor - Scenario: Size is fired at non-full stack actor: almost full stack actor - Scenario: Push is fired at non-full stack actor: almost full stack actor - Scenario: Size is fired at full stack actor - Scenario: Size is fired at non-empty stack actor: full stack actor - Scenario: Peek is fired at non-empty stack actor: full stack actor - Scenario: Pop is fired at non-empty stack actor: full stack actor - Scenario: Push is fired at 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. Although in an
AsyncFeatureSpec
, thefeature
clause is a nesting construct analogous toAsyncFunSpec
'sdescribe
clause, you many sometimes 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 anAsyncFeatureSpec
, you'll need to pass in a prefix or suffix string to add to each test name. You can calltoString
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 previousAsyncFeatureSpecStackBehaviors
example.Given this
AsyncFeatureSpecStackBehaviors
trait, calling it with thealmostEmptyStackActor
fixture, like this: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
almostFullStackActor
fixture, like this: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