Facilitates a “behavior-driven” style of development (BDD), in which tests
are nested inside text clauses denoted with the dash operator (-
).
Implementation trait for class AnyFreeSpec
, which
facilitates a “behavior-driven” style of development (BDD),
in which tests are nested inside text clauses denoted with the dash
operator (-
).
Implementation trait for class AnyFreeSpec
, which
facilitates a “behavior-driven” style of development (BDD),
in which tests are nested inside text clauses denoted with the dash
operator (-
).
AnyFreeSpec
is a class, not a trait,
to minimize compile time given there is a slight compiler overhead to
mixing in traits compared to extending classes. If you need to mix the
behavior of AnyFreeSpec
into some other class, you can use this
trait instead, because class AnyFreeSpec
does nothing more than
extend this trait and add a nice toString
implementation.
See the documentation of the class for a detailed
overview of AnyFreeSpec
.
A sister class to org.scalatest.freespec.AnyFreeSpec
that can pass a fixture object into its tests.
A sister class to org.scalatest.freespec.AnyFreeSpec
that can pass a fixture object into its tests.
Recommended Usage:
Use class FixtureAnyFreeSpec in situations for which AnyFreeSpec
would be a good choice, when all or most tests need the same fixture objects
that must be cleaned up afterwards. Note: FixtureAnyFreeSpec is intended for use in special situations, with class AnyFreeSpec used for general needs. For
more insight into where FixtureAnyFreeSpec fits in the big picture, see the withFixture(OneArgTest) subsection of the Shared fixtures section in the documentation for class AnyFreeSpec .
|
Class FixtureAnyFreeSpec
behaves similarly to class org.scalatest.freespec.AnyFreeSpec
, except that tests may have a
fixture parameter. The type of the
fixture parameter is defined by the abstract FixtureParam
type, which is a member of this class.
This class also has an abstract withFixture
method. This withFixture
method
takes a OneArgTest
, which is a nested trait defined as a member of this class.
OneArgTest
has an apply
method that takes a FixtureParam
.
This apply
method is responsible for running a test.
This class's runTest
method delegates the actual running of each test to withFixture(OneArgTest)
, passing
in the test code to run via the OneArgTest
argument. The withFixture(OneArgTest)
method (abstract in this class) is responsible
for creating the fixture argument and passing it to the test function.
Subclasses of this class must, therefore, do three things differently from a plain old org.scalatest.freespec.AnyFreeSpec
:
FixtureParam
withFixture(OneArgTest)
methodIf the fixture you want to pass into your tests consists of multiple objects, you will need to combine them into one object to use this class. One good approach to passing multiple fixture objects is to encapsulate them in a case class. Here's an example:
case class FixtureParam(file: File, writer: FileWriter)
To enable the stacking of traits that define withFixture(NoArgTest)
, it is a good idea to let
withFixture(NoArgTest)
invoke the test function instead of invoking the test
function directly. To do so, you'll need to convert the OneArgTest
to a NoArgTest
. You can do that by passing
the fixture object to the toNoArgTest
method of OneArgTest
. In other words, instead of
writing “test(theFixture)
”, you'd delegate responsibility for
invoking the test function to the withFixture(NoArgTest)
method of the same instance by writing:
withFixture(test.toNoArgTest(theFixture))
Here's a complete example:
package org.scalatest.examples.freespec.oneargtest import org.scalatest.freespec import java.io._ class ExampleSpec extends freespec.FixtureAnyFreeSpec { case class FixtureParam(file: File, writer: FileWriter) def withFixture(test: OneArgTest) = { // create the fixture val file = File.createTempFile("hello", "world") val writer = new FileWriter(file) val theFixture = FixtureParam(file, writer) try { writer.write("ScalaTest is ") // set up the fixture withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test } finally writer.close() // clean up the fixture } "Testing" - { "should be easy" in { f => f.writer.write("easy!") f.writer.flush() assert(f.file.length === 18) } "should be fun" in { f => f.writer.write("fun!") f.writer.flush() assert(f.file.length === 17) } } }
If a test fails, the OneArgTest
function will result in a Failed wrapping the exception describing the failure.
To ensure clean up happens even if a test fails, you should invoke the test function from inside a try
block and do the cleanup in a
finally
clause, as shown in the previous example.
If multiple test classes need the same fixture, you can define the FixtureParam
and withFixture(OneArgTest)
implementations
in a trait, then mix that trait into the test classes that need it. For example, if your application requires a database and your integration tests
use that database, you will likely have many test classes that need a database fixture. You can create a "database fixture" trait that creates a
database with a unique name, passes the connector into the test, then removes the database once the test completes. This is shown in the following example:
package org.scalatest.examples.fixture.freespec.sharing import java.util.concurrent.ConcurrentHashMap import org.scalatest.fixture import DbServer._ import java.util.UUID.randomUUID object DbServer { // Simulating a database server type Db = StringBuffer private val databases = new ConcurrentHashMap[String, Db] def createDb(name: String): Db = { val db = new StringBuffer databases.put(name, db) db } def removeDb(name: String) { databases.remove(name) } } trait DbFixture { this: fixture.Suite => type FixtureParam = Db // Allow clients to populate the database after // it is created def populateDb(db: Db) {} def withFixture(test: OneArgTest) = { val dbName = randomUUID.toString val db = createDb(dbName) // create the fixture try { populateDb(db) // setup the fixture withFixture(test.toNoArgTest(db)) // "loan" the fixture to the test } finally removeDb(dbName) // clean up the fixture } } class ExampleSpec extends FixtureAnyFreeSpec with DbFixture { override def populateDb(db: Db) { // setup the fixture db.append("ScalaTest is ") } "Testing" - { "should be easy" in { db => db.append("easy!") assert(db.toString === "ScalaTest is easy!") } "should be fun" in { db => db.append("fun!") assert(db.toString === "ScalaTest is fun!") } } // This test doesn't need a Db "Test code" - { "should be clear" in { () => val buf = new StringBuffer buf.append("ScalaTest code is ") buf.append("clear!") assert(buf.toString === "ScalaTest code is clear!") } } }
Often when you create fixtures in a trait like DbFixture
, you'll still need to enable individual test classes
to "setup" a newly created fixture before it gets passed into the tests. A good way to accomplish this is to pass the newly
created fixture into a setup method, like populateDb
in the previous example, before passing it to the test
function. Classes that need to perform such setup can override the method, as does ExampleSpec
.
If a test doesn't need the fixture, you can indicate that by providing a no-arg instead of a one-arg function, as is done in the
third test in the previous example, “Test code should be clear
”. In other words, instead of starting your function literal
with something like “db =>
”, you'd start it with “() =>
”. For such tests, runTest
will not invoke withFixture(OneArgTest)
. It will instead directly invoke withFixture(NoArgTest)
.
Both examples shown above demonstrate 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 these examples. This keeps tests completely isolated, allowing you to run them in parallel if desired. You could mix
ParallelTestExecution
into either of these ExampleSpec
classes, and the tests would run in parallel just fine.
Implementation trait for class FixtureAnyFreeSpec
, which is
a sister class to org.scalatest.freespec.AnyFreeSpec
that can pass a
fixture object into its tests.
Implementation trait for class FixtureAnyFreeSpec
, which is
a sister class to org.scalatest.freespec.AnyFreeSpec
that can pass a
fixture object into its tests.
FixtureAnyFreeSpec
is a class,
not a trait, to minimize compile time given there is a slight compiler
overhead to mixing in traits compared to extending classes. If you need
to mix the behavior of FixtureAnyFreeSpec
into some other
class, you can use this trait instead, because class
FixtureAnyFreeSpec
does nothing more than extend this trait and add a nice toString
implementation.
See the documentation of the class for a detailed
overview of FixtureAnyFreeSpec
.
Facilitates a “behavior-driven” style of development (BDD), in which tests are nested inside text clauses denoted with the dash operator (
-
).AnyFreeSpec
is so named because unlike classes such asAnyWordSpec
,AnyFlatSpec
, andAnyFunSpec
, it is enforces no structure on the text. You are free to compose text however you like. (AAnyFreeSpec
is like free-verse poetry as opposed to a sonnet or haiku, which defines a structure for the text of the poem.)AnyFreeSpec
is a good choice for teams experienced with BDD and able to agree on how to structure the specification text.Here's an example
AnyFreeSpec
:In a
AnyFreeSpec
you write a test with a string followed byin
and the body of the test in curly braces, like this:You can nest a test inside any number of description clauses, which you write with a string followed by a dash character and a block, like this:
You can nest description clauses as deeply as you want. Because the description clause is denoted with an operator, not a word like
should
, you are free to structure the text however you wish. Here's an example:Running the above
StackSpec
in the interpreter would yield:scala> org.scalatest.run(new StackSpec) StackSpec: A Stack whenever it is empty certainly ought to - be empty - complain on peek - complain on pop but when full, by contrast, must - be full - complain on push
A
AnyFreeSpec
can also be used to write a specification-style test in languages other than English. For example:Running the above
ComputerRoomRulesSpec
in the interpreter would yield:scala> org.scalatest.run(new ComputerRoomRulesSpec) ComputerRoomRulesSpec: Achtung! Alle touristen und non-technischen lookenpeepers! - Das machine is nicht fuer fingerpoken und mittengrabben. Is easy - schnappen der springenwerk - blowenfusen - und poppencorken mit spitzen sparken. - Das machine is diggen by experten only. - Is nicht fuer gerwerken by das dummkopfen. - Das rubbernecken sightseeren keepen das cottenpicken hands in das pockets. - Relaxen und watchen das blinkenlights.
A
AnyFreeSpec
'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 while the
AnyFreeSpec
is in its registration phase. Any attempt to register a test after theAnyFreeSpec
has entered its ready phase, i.e., afterrun
has been invoked on theAnyFreeSpec
, will be met with a thrownTestRegistrationClosedException
. The recommended style of usingAnyFreeSpec
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
.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,
AnyFreeSpec
adds a methodignore
to strings that can be used instead ofin
to register a test. For example, to temporarily disable the test with the name"A Stack should pop values in last-in-first-out order"
, just change “in
” 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
AnyFreeSpec
'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 byAnyFreeSpec
'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 specification to the reporter. For example, theGivenWhenThen
trait provides methods that use the implicitinfo
provided byAnyFreeSpec
to pass such information to the reporter. Here's an example:If you run this
AnyFreeSpec
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
AnyFreeSpec
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
AnyFreeSpec
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: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 it is intended to test, has not yet been implemented. You can mark tests as pending in aAnyFreeSpec
like this:If you run this version of
SetSpec
with:It will run both tests but report that
should have size 0
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 a 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
. The reason for this difference is that it enables your unfinished test to sendInfoProvided
messages to the reporter before it completes abruptly withTestPendingException
, as shown in the previous example onInformer
s that used theGivenWhenThen
trait. For example, the following snippet in aAnyFreeSpec
:Would yield the following output when run in the interpreter:
Tagging tests
A
AnyFreeSpec
's tests may be classified into groups by tagging them with string names. As with any suite, when executing aAnyFreeSpec
, groups of tests can optionally be included and/or excluded. To tag aAnyFreeSpec
'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 forAnyFreeSpec
s like this:Given these definitions, you could tag
AnyFreeSpec
tests 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 aAnyFreeSpec
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
FixtureAnyFreeSpec
and overridingwithFixture(OneArgTest)
. Each test in aFixtureAnyFreeSpec
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 forFixtureAnyFreeSpec
.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
AnyFreeSpec
, you first place shared tests in behavior functions. These behavior functions will be invoked during the construction phase of anyAnyFreeSpec
that uses them, so that the tests they contain will be registered as tests in thatAnyFreeSpec
. 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 yourAnyFreeSpec
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 theAnyFreeSpec
that uses them. If they are shared between differentAnyFreeSpec
s, however, you could also define them in a separate trait that is mixed into eachAnyFreeSpec
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
AnyFreeSpec
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 SharedTestExampleSpec) SharedTestExampleSpec: A Stack when empty - should be empty - should complain on peek - should complain on pop when it contains one item should - be non-empty - return the top item on peek - not remove the top item on peek - remove the top item on pop - not be full - add to the top on push when it contains one item less than capacity should - be non-empty - return the top item on peek - not remove the top item on peek - remove the top item on pop - not be full - add to the top on push when full - should be full should - be non-empty - return the top item on peek - not remove the top item on peek - 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
AnyFreeSpec
is to make sure each test is in the context of different surrounding description clauses, because a test's name is the concatenation of its surrounding clauses, followed by the test's text. For example, the following code in aAnyFreeSpec
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 in the context of a different surrounding description (dash) clauses.