package refspec
Type Members
-
class
RefSpec
extends RefSpecLike
Facilitates a “behavior-driven” style of development (BDD), in which tests are methods, optionally nested inside singleton objects defining textual scopes.
Facilitates a “behavior-driven” style of development (BDD), in which tests are methods, optionally nested inside singleton objects defining textual scopes.
Recommended Usage: Class RefSpec
allows you to define tests as methods, which saves one function literal per test compared to style classes that represent tests as functions. Fewer function literals translates into faster compile times and fewer generated class files, which can help minimize build times. As a result, usingRefSpec
can be a good choice in large projects where build times are a concern as well as when generating large numbers of tests programatically via static code generators.Here's an example
RefSpec
:package org.scalatest.examples.spec import org.scalatest.RefSpec class SetSpec extends RefSpec { object `A Set` { object `when empty` { def `should have size 0` { assert(Set.empty.size === 0) } def `should produce NoSuchElementException when head is invoked` { assertThrows[NoSuchElementException] { Set.empty.head } } } } }
A
RefSpec
can contain scopes and tests. You define a scope with a nested singleton object, and a test with a method. The names of both scope objects and test methods must be expressed in back ticks and contain at least one space character.A space placed in backticks is encoded by the Scala compiler as
$u0020
, as illustrated here:scala> def `an example` = () an$u0020example: Unit
RefSpec
uses reflection to discover scope objects and test methods. During discovery,RefSpec
will consider any nested singleton object whose name includes$u0020
a scope object, and any method whose name includes$u0020
a test method. It will ignore any singleton objects or methods that do not include a$u0020
character. Thus,RefSpec
would not consider the following singleton object a scope object:object `Set` { // Not discovered, because no space character }
You can make such a scope discoverable by placing a space at the end, like this:
object `Set ` { // Discovered, because of the trailing space character }
Rather than performing this discovery during construction, when instance variables used by scope objects may as yet be uninitialized,
RefSpec
performs discovery lazily, the first time a method needing the results of discovery is invoked. For example, methodsrun
,runTests
,tags
,expectedTestCount
,runTest
, andtestNames
all ensure that scopes and tests have already been discovered prior to doing anything else. Discovery is performed, and the results recorded, only once for eachRefSpec
instance.A scope 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 name you provide a string (the test text) that specifies one bit of behavior of the subject, and a block of code (the body of the test method) that verifies that behavior.When you execute a
RefSpec
, 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:scala> org.scalatest.run(new SetSpec)
You would see:
A Set when empty - should have size 0 - should produce NoSuchElementException when head is invoked
Or, to run just the test named
A Set when empty should have size 0
, 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:scala> org.scalatest.run(new SetSuite, "size 0") A Set when empty - should have size 0
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 for 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.The test methods shown in this example are parameterless. This is recommended even for test methods with obvious side effects. In production code you would normally declare no-arg, side-effecting methods as empty-paren methods, and call them with empty parentheses, to make it more obvious to readers of the code that they have a side effect. Whether or not a test method has a side effect, however, is a less important distinction than it is for methods in production code. Moreover, test methods are not normally invoked directly by client code, but rather through reflection by running the
Suite
that contains them, so a lack of parentheses on an invocation of a side-effecting test method would not normally appear in any client code. Given the empty parentheses do not add much value in the test methods case, the recommended style is to simply always leave them off.Note: The approach of using backticks around test method names to make it easier to write descriptive test names was inspired by the
SimpleSpec
test framework, originally created by Coda Hale.Ignored tests
To support the common use case of temporarily disabling a test in a
RefSpec
, with the good intention of resurrecting the test at a later time, you can annotate the test method with@Ignore
. For example, to temporarily disable the test method with the name`should have size zero"
, just annotate it with@Ignore
, like this:package org.scalatest.examples.spec.ignore import org.scalatest._ class SetSpec extends RefSpec { object `A Set` { object `when empty` { @Ignore def `should have size 0` { assert(Set.empty.size === 0) } def `should produce NoSuchElementException when head is invoked` { assertThrows[NoSuchElementException] { Set.empty.head } } } } }
If you run this version of
SetSpec
with:scala> org.scalatest.run(new SetSpec)
It will run only the second test and report that the first test was ignored:
A Set when empty - should have size 0 !!! IGNORED !!! - should produce NoSuchElementException when head is invoked
If you wish to temporarily ignore an entire suite of tests, you can annotate the test class with
@Ignore
, like this:package org.scalatest.examples.spec.ignoreall import org.scalatest._ @Ignore class SetSpec extends RefSpec { object `A Set` { object `when empty` { def `should have size 0` { assert(Set.empty.size === 0) } def `should produce NoSuchElementException when head is invoked` { assertThrows[NoSuchElementException] { Set.empty.head } } } } }
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:scala> org.scalatest.run(new SetSpec) SetSpec: A Set when empty - should have size 0 !!! IGNORED !!! - should produce NoSuchElementException when head is invoked !!! IGNORED !!!
Note that marking a test class as ignored won't prevent it from being discovered by ScalaTest. Ignored classes will be discovered and run, and all their tests will be reported as ignored. This is intended to keep the ignored class visible, to encourage the developers to eventually fix and “un-ignore” it. If you want to prevent a class from being discovered at all, use the
DoNotDiscover
annotation instead.Informers
One of the objects to
RefSpec
'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 byRefSpec
'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
:package org.scalatest.examples.spec.info import collection.mutable import org.scalatest._ class SetSpec extends RefSpec with GivenWhenThen { object `A mutable Set` { def `should allow an element to be added` { Given("an empty mutable Set") val set = mutable.Set.empty[String] When("an element is added") set += "clarity" Then("the Set should have size 1") assert(set.size === 1) And("the Set should contain the added element") assert(set.contains("clarity")) info("That's all folks!") } } }
If you run this
RefSpec
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
RefSpec
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
RefSpec
that usesmarkup
:package org.scalatest.examples.spec.markup import collection.mutable import org.scalatest._ class SetSpec extends RefSpec with GivenWhenThen { markup { """ Mutable Set ———-- A set is a collection that contains no duplicate elements. To implement a concrete mutable set, you need to provide implementations of the following methods: def contains(elem: A): Boolean def iterator: Iterator[A] def += (elem: A): this.type def -= (elem: A): this.type If you wish that methods like `take`, `drop`, `filter` return the same kind of set, you should also override: def empty: This It is also good idea to override methods `foreach` and `size` for efficiency. """ } object `A mutable Set` { def `should allow an element to be added` { Given("an empty mutable Set") val set = mutable.Set.empty[String] When("an element is added") set += "clarity" Then("the Set should have size 1") assert(set.size === 1) And("the Set should contain the added element") assert(set.contains("clarity")) markup("This test finished with a **bold** statement!") } } }
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:package org.scalatest.examples.spec.note import collection.mutable import org.scalatest._ class SetSpec extends RefSpec { object `A mutable Set` { def `should allow an element to be added` { info("info is recorded") markup("markup is *also* recorded") note("notes are sent immediately") alert("alerts are also sent immediately") val set = mutable.Set.empty[String] set += "clarity" assert(set.size === 1) assert(set.contains("clarity")) } } }
Because
note
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:scala> org.scalatest.run(new SetSpec) SetSpec: A mutable Set + notes are sent immediately + alerts are also sent immediately - should allow an element to be added + info is recorded + markup is *also* recorded
Another example is slowpoke notifications. If you find a test is taking a long time to complete, but you're not sure which test, you can enable slowpoke notifications. ScalaTest will use an
Alerter
to fire an event whenever a test has been running longer than a specified amount of time.In summary, use
info
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. (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
RefSpec
by using "{ pending }
" as the body of the test method, like this:package org.scalatest.examples.spec.pending import org.scalatest._ class SetSpec extends RefSpec { object `A Set` { object `when empty` { def `should have size 0` { pending } def `should produce NoSuchElementException when head is invoked` { assertThrows[NoSuchElementException] { Set.empty.head } } } } }
(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:scala> org.scalatest.run(new SetSpec)
It will run both tests, but report that test "
should have size 0
" is pending. You'll see:A Set when empty - should have size 0 (pending) - should produce NoSuchElementException when head is invoked
Tagging tests
A
RefSpec
's tests may be classified into groups by tagging them with string names. When executing aRefSpec
, groups of tests can optionally be included and/or excluded. In this trait's implementation, tags are indicated by annotations attached to the test method. To create a new tag type to use inRefSpec
s, simply define a new Java annotation that itself is annotated with theorg.scalatest.TagAnnotation
annotation. (Currently, for annotations to be visible in Scala programs via Java reflection, the annotations themselves must be written in Java.) For example, to create tags namedSlowTest
andDbTest
, you would write in Java:package org.scalatest.examples.spec.tagging; import java.lang.annotation.*; import org.scalatest.TagAnnotation; @TagAnnotation @Retention(RetentionPolicy.RUNTIME) @Target({ElementType.METHOD, ElementType.TYPE}) public @interface SlowTest {} @TagAnnotation @Retention(RetentionPolicy.RUNTIME) @Target({ElementType.METHOD, ElementType.TYPE}) public @interface DbTest {}
Given these annotations, you could tag
RefSpec
tests like this:package org.scalatest.examples.spec.tagging import org.scalatest.RefSpec class SetSpec extends RefSpec { object `A Set` { object `when empty` { @SlowTest def `should have size 0` { assert(Set.empty.size === 0) } @SlowTest @DbTest def `should produce NoSuchElementException when head is invoked` { assertThrows[NoSuchElementException] { Set.empty.head } } } } }
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 with tags listed in thetagsToExclude
Set
. IftagsToInclude
is defined, only tests with tags mentioned in thetagsToInclude
set, and not mentioned intagsToExclude
, will be run.A tag annotation also allows you to tag all the tests of a
RefSpec
in one stroke by annotating the class. For more information and examples, see the documentation for classTag
.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:
- Refactor using Scala
- Override
withFixture
- Mix in a before-and-after trait
Each technique is geared towards helping you reduce code duplication without introducing instance
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:
Refactor using Scala when different tests need different fixtures. get-fixture methods The extract method refactor helps you create a fresh instances of mutable fixture objects in each test that needs them, but doesn't help you clean them up when you're done. fixture-context objects By placing fixture methods and fields into traits, you can easily give each test just the newly created fixtures it needs by mixing together traits. Use this technique when you need different combinations of mutable fixture objects in different tests, and don't need to clean up after. loan-fixture methods Factor out dupicate code with the loan pattern when different tests need different fixtures that must be cleaned up afterwards. Override withFixture
when most or all tests need the same fixture.withFixture(NoArgTest)
The recommended default approach when most or all tests need the same fixture treatment. This general technique allows you, for example, to perform side effects at the beginning and end of all or most tests, transform the outcome of tests, retry tests, make decisions based on test names, tags, or other test data. Use this technique unless: - Different tests need different fixtures (refactor using Scala instead)
- An exception in fixture code should abort the suite, not fail the test (use a before-and-after trait instead)
- You have objects to pass into tests (override
withFixture(OneArgTest)
instead)
withFixture(OneArgTest)
Use when you want to pass the same fixture object or objects as a parameter into all or most tests. Mix in a before-and-after trait when you want an aborted suite, not a failed test, if the fixture code fails. BeforeAndAfter
Use this boilerplate-buster when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests. BeforeAndAfterEach
Use when you want to stack traits that perform the same side-effects before and/or after tests, rather than at the beginning or end of tests. Calling get-fixture methods
If you need to create the same mutable fixture objects in multiple tests, and don't need to clean them up after using them, the simplest approach is to write one or more get-fixture methods. A get-fixture method returns a new instance of a needed fixture object (or a holder object containing multiple fixture objects) each time it is called. You can call a get-fixture method at the beginning of each test that needs the fixture, storing the returned object or objects in local variables. Here's an example:
package org.scalatest.examples.spec.getfixture import org.scalatest.RefSpec import collection.mutable.ListBuffer class ExampleSpec extends RefSpec { class Fixture { val builder = new StringBuilder("ScalaTest is ") val buffer = new ListBuffer[String] } def fixture = new Fixture object `Testing ` { def `should be easy` { val f = fixture f.builder.append("easy!") assert(f.builder.toString === "ScalaTest is easy!") assert(f.buffer.isEmpty) f.buffer += "sweet" } def `should be fun` { val f = fixture f.builder.append("fun!") assert(f.builder.toString === "ScalaTest is fun!") assert(f.buffer.isEmpty) } } }
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, 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:
package org.scalatest.examples.spec.fixturecontext import collection.mutable.ListBuffer import org.scalatest.RefSpec class ExampleSpec extends RefSpec { trait Builder { val builder = new StringBuilder("ScalaTest is ") } trait Buffer { val buffer = ListBuffer("ScalaTest", "is") } object `Testing ` { // This test needs the StringBuilder fixture def `should be productive` { new Builder { builder.append("productive!") assert(builder.toString === "ScalaTest is productive!") } } } object `Test code` { // This test needs the ListBuffer[String] fixture def `should be readable` { new Buffer { buffer += ("readable!") assert(buffer === List("ScalaTest", "is", "readable!")) } } // This test needs both the StringBuilder and ListBuffer def `should be clear and concise` { new Builder with Buffer { builder.append("clear!") buffer += ("concise!") assert(builder.toString === "ScalaTest is clear!") assert(buffer === List("ScalaTest", "is", "concise!")) } } } }
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:// Default implementation in trait Suite protected def withFixture(test: NoArgTest) = { test() }
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:// Your implementation override def withFixture(test: NoArgTest) = { // Perform setup try super.withFixture(test) // Invoke the test function finally { // Perform cleanup } }
Here's an example in which
withFixture(NoArgTest)
is used to take a snapshot of the working directory if a test fails, and and send that information to the reporter:package org.scalatest.examples.spec.noargtest import java.io.File import org.scalatest._ class ExampleSpec extends RefSpec { override def withFixture(test: NoArgTest) = { super.withFixture(test) match { case failed: Failed => val currDir = new File(".") val fileNames = currDir.list() info("Dir snapshot: " + fileNames.mkString(", ")) failed case other => other } } object `This test` { def `should succeed` { assert(1 + 1 === 2) } def `should fail` { assert(1 + 1 === 3) } } }
Running this version of
ExampleSuite
in the interpreter in a directory with two files,hello.txt
andworld.txt
would give the following output:scala> org.scalatest.run(new ExampleSuite) ExampleSuite: This test - should fail *** FAILED *** 2 did not equal 3 (
:33) + Dir snapshot: hello.txt, world.txt - should succeedNote 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
.)package org.scalatest.examples.spec.loanfixture import java.util.concurrent.ConcurrentHashMap 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) } } import org.scalatest.RefSpec import DbServer._ import java.util.UUID.randomUUID import java.io._ class ExampleSpec extends RefSpec { def withDatabase(testCode: Db => Any) { val dbName = randomUUID.toString val db = createDb(dbName) // create the fixture try { db.append("ScalaTest is ") // perform setup testCode(db) // "loan" the fixture to the test } finally removeDb(dbName) // clean up the fixture } def withFile(testCode: (File, FileWriter) => Any) { val file = File.createTempFile("hello", "world") // create the fixture val writer = new FileWriter(file) try { writer.write("ScalaTest is ") // set up the fixture testCode(file, writer) // "loan" the fixture to the test } finally writer.close() // clean up the fixture } object `Testing ` { // This test needs the file fixture def `should be productive` { withFile { (file, writer) => writer.write("productive!") writer.flush() assert(file.length === 24) } } } object `Test code` { // This test needs the database fixture def `should be readable` { withDatabase { db => db.append("readable!") assert(db.toString === "ScalaTest is readable!") } } // This test needs both the file and the database def `should be clear and concise` { withDatabase { db => withFile { (file, writer) => // loan-fixture methods compose db.append("clear!") writer.write("concise!") writer.flush() assert(db.toString === "ScalaTest is clear!") assert(file.length === 21) } } } } }
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)
fixture.Spec
is deprecated, please usefixture.FunSpec
instead.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:package org.scalatest.examples.spec.beforeandafter import org.scalatest.RefSpec import org.scalatest.BeforeAndAfter import collection.mutable.ListBuffer class ExampleSpec extends RefSpec with BeforeAndAfter { val builder = new StringBuilder val buffer = new ListBuffer[String] before { builder.append("ScalaTest is ") } after { builder.clear() buffer.clear() } object `Testing ` { def `should be easy` { builder.append("easy!") assert(builder.toString === "ScalaTest is easy!") assert(buffer.isEmpty) buffer += "sweet" } def `should be fun` { builder.append("fun!") assert(builder.toString === "ScalaTest is fun!") assert(buffer.isEmpty) } } }
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 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
:package org.scalatest.examples.spec.composingwithfixture import org.scalatest._ import collection.mutable.ListBuffer trait Builder extends TestSuiteMixin { this: TestSuite => val builder = new StringBuilder abstract override def withFixture(test: NoArgTest) = { builder.append("ScalaTest is ") try super.withFixture(test) // To be stackable, must call super.withFixture finally builder.clear() } } trait Buffer extends TestSuiteMixin { this: TestSuite => val buffer = new ListBuffer[String] abstract override def withFixture(test: NoArgTest) = { try super.withFixture(test) // To be stackable, must call super.withFixture finally buffer.clear() } } class ExampleSpec extends RefSpec with Builder with Buffer { object `Testing ` { def `should be easy` { builder.append("easy!") assert(builder.toString === "ScalaTest is easy!") assert(buffer.isEmpty) buffer += "sweet" } def `should be fun` { builder.append("fun!") assert(builder.toString === "ScalaTest is fun!") assert(buffer.isEmpty) buffer += "clear" } } }
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:class Example2Spec extends RefSpec with Buffer with Builder
And if you only need one fixture you mix in only that trait:
class Example3Spec extends RefSpec with Builder
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
:package org.scalatest.examples.spec.composingbeforeandaftereach import org.scalatest._ import org.scalatest.BeforeAndAfterEach import collection.mutable.ListBuffer trait Builder extends BeforeAndAfterEach { this: Suite => val builder = new StringBuilder override def beforeEach() { builder.append("ScalaTest is ") super.beforeEach() // To be stackable, must call super.beforeEach } override def afterEach() { try super.afterEach() // To be stackable, must call super.afterEach finally builder.clear() } } trait Buffer extends BeforeAndAfterEach { this: Suite => val buffer = new ListBuffer[String] override def afterEach() { try super.afterEach() // To be stackable, must call super.afterEach finally buffer.clear() } } class ExampleSpec extends RefSpec with Builder with Buffer { object `Testing ` { def `should be easy` { builder.append("easy!") assert(builder.toString === "ScalaTest is easy!") assert(buffer.isEmpty) buffer += "sweet" } def `should be fun` { builder.append("fun!") assert(builder.toString === "ScalaTest is fun!") assert(buffer.isEmpty) buffer += "clear" } } }
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
Because
RefSpec
represents tests as methods, you cannot share or otherwise dynamically generate tests. Instead, use static code generation if you want to generate tests in aRefSpec
. In other words, write a program that statically generates the entire source file of aRefSpec
subclass. -
trait
RefSpecLike
extends TestSuite with Informing with Notifying with Alerting with Documenting
Implementation trait for class
RefSpec
, which facilitates a “behavior-driven” style of development (BDD), in which tests are methods, optionally nested inside singleton objects defining textual scopes.Implementation trait for class
RefSpec
, which facilitates a “behavior-driven” style of development (BDD), in which tests are methods, optionally nested inside singleton objects defining textual scopes.RefSpec
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 ofRefSpec
into some other class, you can use this trait instead, because classRefSpec
does nothing more than extend this trait and add a nicetoString
implementation.See the documentation of the class for a detailed overview of
RefSpec
.