Class that, via an instance referenced from the it
field,
supports test (and shared test) registration in AnyFunSpec
s.
Class that, via an instance referenced from the it
field,
supports test (and shared test) registration in AnyFunSpec
s.
This class supports syntax such as the following test registration:
it("should be empty") ^
and the following shared test registration:
it should behave like nonFullStack(stackWithOneItem) ^
For more information and examples, see the main documentation for AnyFunSpec
.
Class that, via an instance referenced from the they
field,
supports test (and shared test) registration in AnyFunSpec
s.
Class that, via an instance referenced from the they
field,
supports test (and shared test) registration in AnyFunSpec
s.
This class supports syntax such as the following test registration:
they("should be empty") ^
and the following shared test registration:
they should behave like nonFullStack(stackWithOneItem) ^
For more information and examples, see the main documentation for AnyFunSpec
.
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
AnyFunSpec
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.
Supports shared test registration in AnyFunSpec
s.
Supports shared test registration in AnyFunSpec
s.
This field supports syntax such as the following:
it should behave like nonFullStack(stackWithOneItem) ^
For more information and examples of the use of <cod>behave, see the Shared tests section in the main documentation for this trait.
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 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 AnyFunSpec
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
DuplicateTestNameException
if a test with the same name has been registered previously
NullArgumentException
if specText
or any passed test tag is null
TestRegistrationClosedException
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.
Supports test (and shared test) registration in AnyFunSpec
s.
Supports test (and shared test) registration in AnyFunSpec
s.
This field supports syntax such as the following:
it("should be empty") ^
class="stExamples" it should behave like nonFullStack(stackWithOneItem) ^
For more information and examples of the use of the it
field, see the main documentation for this trait.
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
AnyFunSpec
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 .
NullArgumentException
if any of testName
, reporter
, stopper
, or configMap
is null
.
Run zero to many of this AnyFunSpec
's tests.
Run zero to many of this AnyFunSpec
's tests.
an 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.
IllegalArgumentException
if testName
is defined, but no test with the specified test name
exists in this Suite
NullArgumentException
if any of the passed parameters is null
.
Suite style name.
A Map
whose keys are String
names of tagged tests and whose associated values are
the Set
of tags for the test.
A Map
whose keys are String
names of tagged tests and whose associated values are
the Set
of tags for the test. If this AnyFunSpec
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 it
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 AnyFunSpec
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 AnyFunSpec
:
import org.scalatest.funspec.AnyFunSpec class StackSpec extends AnyFunSpec { describe("A Stack") { describe("(when not empty)") { it("must allow me to pop") {} } describe("(when not full)") { it("must allow me to push") {} } } }
Invoking testNames
on this AnyFunSpec
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"
Supports test (and shared test) registration in AnyFunSpec
s.
Supports test (and shared test) registration in AnyFunSpec
s.
This field supports syntax such as the following:
they("should be empty") ^
class="stExamples" it should behave like nonFullStack(stackWithOneItem) ^
For more information and examples of the use of the it
field, see the main documentation for this trait.
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.
(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.
Facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.
AnyFunSpec
will feel familiar and comfortable; More generally, for any team that prefers BDD,AnyFunSpec
's nesting and gentle guide to structuring text (withdescribe
andit
) provide an excellent general-purpose choice for writing specification-style tests.Here's an example
AnyFunSpec
:A
AnyFunSpec
contains describe clauses and tests. You define a describe clause withdescribe
, and a test with eitherit
orthey
.describe
,it
, andthey
are methods, defined inAnyFunSpec
, which will be invoked by the primary constructor ofSetSpec
. A describe clause names, or gives more information about, the subject (class or other entity) you are specifying and testing. In the previous example,"A Set"
is the subject under specification and test. With each test you provide a string (the spec text) that specifies one bit of behavior of the subject, 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 toit
(orthey
), which will register the test for later execution.Note: the
they
method is intended for use when the subject is plural, for example:A
AnyFunSpec
'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.Tests can only be registered with the
it
orthey
methods while theAnyFunSpec
is in its registration phase. Any attempt to register a test after theAnyFunSpec
has entered its ready phase, i.e., afterrun
has been invoked on theAnyFunSpec
, will be met with a thrownTestRegistrationClosedException
. The recommended style of usingAnyFunSpec
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
.When you execute a
AnyFunSpec
, 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 runSetSpec
from within the Scala interpreter:You would see:
Or, to run just the “
A Set when empty should have size 0
” test, you could pass that test's name, or any unique substring of the name, such as"size 0"
or even just"0"
. Here's an example:You can also pass to
execute
a config map of key-value pairs, which will be passed down into suites and tests, as well as other parameters that configure the run itself. For more information on running in the Scala interpreter, see the documentation forexecute
(below) and the ScalaTest shell.The
execute
method invokes arun
method that takes two parameters. Thisrun
method, which actually executes the suite, will usually be invoked by a test runner, such asrun
,tools.Runner
, a build tool, or an IDE.Note:
AnyFunSpec
's syntax is in great part inspired by RSpec, a Ruby BDD framework.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,
AnyFunSpec
provides registration methods that start withignore
instead ofit
orthey
. For example, to temporarily disable the test with the text"should have size 0"
, just change “it
” into “ignore
,” like this:If you run this version of
SetSpec
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
SetSpec
in the above example with the@Ignore
tag annotation means that both tests in the class will be ignored. If you run the aboveSetSpec
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.Informers
One of the parameters to
AnyFunSpec
'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 reporting done by default byAnyFunSpec
'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 one of itsapply
methods. TheInformer
will then pass the information to theReporter
via anInfoProvided
event. Here's an example in which theInformer
returned byinfo
is used implicitly by theGiven
,When
, andThen
methods of traitGivenWhenThen
:If you run this
AnyFunSpec
from the interpreter, you will see the following output:scala> org.scalatest.run(new SetSpec) A mutable Set - should allow an element to be added + 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
AnyFunSpec
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
AnyFunSpec
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. The test can also include some code that sends more information about the behavior to the reporter when the tests run. 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.You can mark a test as pending in
AnyFunSpec
by placing "(pending)
" after the test name, like this:(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 ofSetSpec
with:It will run both tests, but report that the test named "
should have size 0
" is pending. You'll see:Tagging tests
A
AnyFunSpec
's tests may be classified into groups by tagging them with string names. As with any suite, when executing aAnyFunSpec
, groups of tests can optionally be included and/or excluded. To tag aAnyFunSpec
'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 forAnyFunSpec
s like this:Given these definitions, you could place
AnyFunSpec
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 aAnyFunSpec
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:
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 more amenable for parallel test execution.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(NoArgTest)
withFixture(OneArgTest)
instead)withFixture(OneArgTest)
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 an 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:
The “
f.
” in front of each use of a fixture object provides a visual indication of which objects are part of the fixture, but if you prefer, you can import the the members with “import f._
” and use the names directly.If you need to configure fixture objects differently in different tests, you can pass configuration into the get-fixture method. For example, if you could pass in an initial value for a mutable fixture object as a parameter to the get-fixture method.
Instantiating fixture-context objects
An alternate technique that is especially useful when different tests need different combinations of fixture objects is to define the fixture objects as instance variables of fixture-context objects whose instantiation forms the body of tests. Like get-fixture methods, fixture-context objects are only appropriate if you don't need to clean up the fixtures after using them.
To use this technique, you define instance variables intialized with fixture objects in traits and/or classes, then in each test instantiate an object that contains just the fixture objects needed by the test. Traits allow you to mix together just the fixture objects needed by each test, whereas classes allow you to pass data in via a constructor to configure the fixture objects. Here's an example in which fixture objects are partitioned into two traits and each test just mixes together the traits it needs:
Overriding
withFixture(NoArgTest)
Although the get-fixture method and fixture-context object approaches take care of setting up a fixture at the beginning of each test, they don'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(NoArgTest)
, one of ScalaTest's lifecycle methods defined in traitSuite
.Trait
Suite
's implementation ofrunTest
passes a no-arg test function towithFixture(NoArgTest)
. It iswithFixture
's responsibility to invoke that test function.Suite
's implementation ofwithFixture
simply invokes the function, like this:You can, therefore, override
withFixture
to perform setup before and/or cleanup after invoking the test function. If you have cleanup to perform, you should invoke the test function inside atry
block and perform the cleanup in afinally
clause, in case an exception propagates back throughwithFixture
. (If a test fails because of an exception, the test function invoked by withFixture will result in aFailed
wrapping the exception. Nevertheless, best practice is to perform cleanup in a finally clause just in case an exception occurs.)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:Here's an example in which
withFixture(NoArgTest)
is used to take a snapshot of the working directory if a test fails, and send that information to the reporter:Running this version of
ExampleSuite
in the interpreter in a directory with two files,hello.txt
andworld.txt
would give the following output:Note that the
NoArgTest
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.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 files or databases, it is a good idea to give each file or 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
FixtureSuite
and overridingwithFixture(OneArgTest)
. Each test in aFixtureSuite
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 aOneArgTest
. ThiswithFixture
method is responsible for invoking the one-arg test function, so you can perform fixture set up before, and clean up after, invoking and passing the fixture into the test function.To enable the stacking of traits that define
withFixture(NoArgTest)
, it is a good idea to letwithFixture(NoArgTest)
invoke the test function instead of invoking the test function directly. To do so, you'll need to convert theOneArgTest
to aNoArgTest
. You can do that by passing the fixture object to thetoNoArgTest
method ofOneArgTest
. In other words, instead of writing “test(theFixture)
”, you'd delegate responsibility for invoking the test function to thewithFixture(NoArgTest)
method of the same instance by writing:Here's a complete example:
In this example, the tests actually required two fixture objects, a
File
and aFileWriter
. In such situations you can simply define theFixtureParam
type to be a tuple containing the objects, or as is done in this example, a case class containing the objects. For more information on thewithFixture(OneArgTest)
technique, see the documentation forFixtureAnyFunSpec
.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. This is why ScalaTest'sParallelTestExecution
trait extendsOneInstancePerTest
. By running each test in its own instance of the class, each test has its own copy of the instance variables, so you don't need to synchronize. If you mixedParallelTestExecution
into theExampleSuite
above, the tests would run in parallel just fine without any synchronization needed on the mutableStringBuilder
andListBuffer[String]
objects.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 theStringBuilder
andListBuffer[String]
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,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” toBuffer
. If you wantedBuffer
to be “super” toBuilder
, you need only switch the order you mix them together, like this:And 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 a
AnyFunSpec
, you first place shared tests in behavior functions. These behavior functions will be invoked during the construction phase of anyAnyFunSpec
that uses them, so that the tests they contain will be registered as tests in thatAnyFunSpec
. For example, given this stack class:You may want to test the
Stack
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 yourAnyFunSpec
for stack, 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 theAnyFunSpec
that uses them. If they are shared between differentAnyFunSpec
s, however, you could also define them in a separate trait that is mixed into eachAnyFunSpec
that uses them.For example, here the
nonEmptyStack
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
AnyFunSpec
offers a DSL for the purpose, which looks like this:If you prefer to use an imperative style to change fixtures, for example by mixing in
BeforeAndAfterEach
and reassigning astack
var
inbeforeEach
, you could write your behavior functions in the context of thatvar
, which means you wouldn't need to pass in the stack fixture because it would be in scope already inside the behavior function. In that case, your code would look like this:The recommended style, however, is the functional, pass-all-the-needed-values-in style. 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) A Stack (when empty) - should be empty - should complain on peek - should complain on pop A Stack (with one item) - should be non-empty - should return the top item on peek - should not remove the top item on peek - should remove the top item on pop - should not be full - should add to the top on push A Stack (with one item less than capacity) - should be non-empty - should return the top item on peek - should not remove the top item on peek - should remove the top item on pop - should not be full - should add to the top on push A Stack (full) - should be full - should be non-empty - should return the top item on peek - should not remove the top item on peek - should remove the top item on pop - should complain on a push
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. A good way to solve this problem in a
AnyFunSpec
is to surround each invocation of a behavior function with adescribe
clause, which will prepend a string to each test name. For example, the following code in aAnyFunSpec
would register a test with the name"A Stack (when empty) should be empty"
:If the
"should be empty"
test was factored out into a behavior function, it could be called repeatedly so long as each invocation of the behavior function is inside a different set ofdescribe
clauses.