import org.scalatest.WordSpec
 import scala.collection.mutable.Stack

 class StackSpec extends WordSpec {

   "A Stack" should {

     "pop values in last-in-first-out order" in {
       val stack = new Stack[Int]
       stack.push(1)
       stack.push(2)
       assert(stack.pop() === 2)
       assert(stack.pop() === 1)
     }

     "throw NoSuchElementException if an empty stack is popped" in {
       val emptyStack = new Stack[String]
       intercept[NoSuchElementException] {
         emptyStack.pop()
       }
     }
   }
 }
 

Note: Trait WordSpec is in part inspired by class org.specs.Specification, designed by Eric Torreborre for the Specs framework.

In a WordSpec you write a one (or more) sentence specification for each bit of behavior you wish to specify and test. Each specification sentence has a "subject," which is sometimes called the system under test (or SUT). The subject is entity being specified and tested and also serves as the subject of the sentences you write for each test. A subject can be followed by one of three verbs, should, must, or can, and a block. Here are some examples:

 "A Stack" should {
   // ...
 }
 "An Account" must {
   // ...
 }
 "A ShippingManifest" can {
   // ...
 }
 

You can describe a subject in varying situations by using a when clause. A when clause follows the subject and precedes a block. In the block after the when, you place strings that describe a situation or a state the subject may be in using a string, each followed by a verb. Here's an example:

 "A Stack" when {
   "empty" should {
     // ...
   }
   "non-empty" should {
     // ...
   }
   "full" should {
     // ...
   }
 }
 

When you are ready to finish a sentence, you write a string followed by in and a block that contains the code of the test. Here's an example:

 import org.scalatest.WordSpec
 
 class StackSpec extends WordSpec {
   "A Stack" when {
     "empty" should {
       "be empty" in {
         // ...
       }
       "complain on peek" in {
         // ...
       }
       "complain on pop" in {
         // ...
       }
     }
     "full" should {
       "be full" in {
         // ...
       }
       "complain on push" in {
         // ...
       }
     }
   }
 }
 

Running the above StackSpec in the interpreter would yield:

 scala> (new StackSpec).execute()
 A Stack (when empty) 
 - should be empty 
 - should complain on peek
 - should complain on pop
 A Stack (when full) 
 - should be full
 - should complain on push
 

Note that the output does not exactly match the input in an effort to maximize readability. Although the WordSpec code is nested, which can help you eliminate any repeated phrases in the specification portion of your code, the output printed will have one line per subject per situation, and one line per test.

Sometimes you may wish to eliminate repeated phrases inside the block following a verb. Here's an example in which the phrase "provide an and/or operator that" is repeated:

 import org.scalatest.WordSpec
 
 class AndOrSpec extends WordSpec {
 
   "The ScalaTest Matchers DSL" should {
     "provide an and operator that returns silently when evaluating true and true" in {}
     "provide an and operator that throws a TestFailedException when evaluating true and false" in {}
     "provide an and operator that throws a TestFailedException when evaluating false and true" in {}
     "provide an and operator that throws a TestFailedException when evaluating false and false" in {}
     "provide an or operator that returns silently when evaluating true or true" in {}
     "provide an or operator that returns silently when evaluating true or false" in {}
     "provide an or operator that returns silently when evaluating false or true" in {}
     "provide an or operator that throws a TestFailedException when evaluating false or false" in {}
   }
 }
 

In such situations you can place that clauses inside the verb clause, like this:

 import org.scalatest.WordSpec
 
 class AndOrSpec extends WordSpec {

   "The ScalaTest Matchers DSL" should {
     "provide an and operator" that {
       "returns silently when evaluating true and true" in {}
       "throws a TestFailedException when evaluating true and false" in {}
       "that throws a TestFailedException when evaluating false and true" in {}
       "throws a TestFailedException when evaluating false and false" in {}
     }
     "provide an or operator" that {
       "returns silently when evaluating true or true" in {}
       "returns silently when evaluating true or false" in {}
       "returns silently when evaluating false or true" in {}
       "throws a TestFailedException when evaluating false or false" in {}
     }
   }
 }
 

If a word or phrase is repeated at the beginning of each string contained in a block, you can eliminate that repetition by using an after word. An after word is a word or phrase that you can place after when, a verb, or that. For example, in the previous WordSpec, the word "provide" is repeated at the beginning of each string inside the should block. You can factor out this duplication like this:

 import org.scalatest.WordSpec
 
 class AndOrSpec extends WordSpec {
 
    def provide = afterWord("provide")
 
   "The ScalaTest Matchers DSL" should provide {
     "an and operator" that {
       "returns silently when evaluating true and true" in {}
       "throws a TestFailedException when evaluating true and false" in {}
       "that throws a TestFailedException when evaluating false and true" in {}
       "throws a TestFailedException when evaluating false and false" in {}
     }
     "an or operator" that {
       "returns silently when evaluating true or true" in {}
       "returns silently when evaluating true or false" in {}
       "returns silently when evaluating false or true" in {}
       "throws a TestFailedException when evaluating false or false" in {}
     }
   }
 }
 

Once you've defined an after word, you can place it after when, a verb (should, must, or can), or that. (You can't place one after in or is, the words that introduce a test.) Here's an example that has after words used in all three places:

 import org.scalatest.WordSpec
 
 class ScalaTestGUISpec extends WordSpec {
 
   def theUser = afterWord("the user")
   def display = afterWord("display")
   def is = afterWord("is")
 
   "The ScalaTest GUI" when theUser {
     "clicks on an event report in the list box" should display {
       "a blue background in the clicked-on row in the list box" in {}
       "the details for the event in the details area" in {}
       "a rerun button" that is {
         "enabled if the clicked-on event is rerunnable" in {}
         "disabled if the clicked-on event is not rerunnable" in {}
       }
     }
   }
 }
 

Running the previous WordSpec in the Scala interpreter would yield:

 scala> (new ScalaTestGUISpec).execute()
 The ScalaTest GUI (when the user clicks on an event report in the list box) 
 - should display a blue background in the clicked-on row in the list box
 - should display the details for the event in the details area
 - should display a rerun button that is enabled if the clicked-on event is rerunnable
 - should display a rerun button that is disabled if the clicked-on event is not rerunnable
 

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

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

Shared fixtures

A test fixture is objects or other artifacts (such as files, sockets, database connections, etc.) used by tests to do their work. You can use fixtures in WordSpecs with the same approaches suggested for Suite in its documentation. The same text that appears in the test fixture section of Suite's documentation is repeated here, with examples changed from Suite to WordSpec.

If a fixture is used by only one test, then the definitions of the fixture objects can be local to the test function, such as the objects assigned to stack and emptyStack in the previous StackSpec examples. If multiple tests need to share an immutable fixture, one approach is to assign them to instance variables. Here's a (very contrived) example, in which the object assigned to shared is used by multiple test functions:

 import org.scalatest.WordSpec

 class ArithmeticSpec extends WordSpec {

   // Sharing immutable fixture objects via instance variables
   val shared = 5

  "The Scala language" should {
     "add correctly" in {
       val sum = 2 + 3
       assert(sum === shared)
     }

     "subtract correctly" in {
       val diff = 7 - 2
       assert(diff === shared)
     }
   }
 }
 

In some cases, however, shared mutable fixture objects may be changed by tests such that they need to be recreated or reinitialized before each test. Shared resources such as files or database connections may also need to be created and initialized before, and cleaned up after, each test. JUnit offers methods setUp and tearDown for this purpose. In ScalaTest, you can use the BeforeAndAfterEach trait, which will be described later, to implement an approach similar to JUnit's setUp and tearDown, however, this approach often involves reassigning vars between tests. Before going that route, you should consider some approaches that avoid vars. One approach is to write one or more create-fixture methods that return a new instance of a needed object (or a tuple or case class holding new instances of multiple objects) each time it is called. You can then call a create-fixture method at the beginning of each test that needs the fixture, storing the fixture object or objects in local variables. Here's an example:

 import org.scalatest.WordSpec
 import scala.collection.mutable.ListBuffer

 class MySuite extends WordSpec {

   // create objects needed by tests and return as a tuple
   def createFixture = (
     new StringBuilder("ScalaTest is "),
     new ListBuffer[String]
   )

  "ScalaTest" should {

     "be easy " in {
       val (builder, lbuf) = createFixture
       builder.append("easy!")
       assert(builder.toString === "ScalaTest is easy!")
       assert(lbuf.isEmpty)
       lbuf += "sweet"
     }

     "be fun" in {
       val (builder, lbuf) = createFixture
       builder.append("fun!")
       assert(builder.toString === "ScalaTest is fun!")
       assert(lbuf.isEmpty)
     }
   }
 }
 

If different tests in the same WordSpec require different fixtures, you can create multiple create-fixture methods and call the method (or methods) needed by each test at the begining of the test. If every test requires the same set of mutable fixture objects, one other approach you can take is make them simply vals and mix in trait OneInstancePerTest. If you mix in OneInstancePerTest, each test will be run in its own instance of the WordSpec, similar to the way JUnit tests are executed.

Although the create-fixture and OneInstancePerTest approaches take care of setting up a fixture before each test, they don't address the problem of cleaning up a fixture after the test completes. In this situation, one option is to mix in the BeforeAndAfterEach trait. BeforeAndAfterEach's beforeEach method will be run before, and its afterEach method after, each test (like JUnit's setUp and tearDown methods, respectively). For example, you could create a temporary file before each test, and delete it afterwords, like this:

 import org.scalatest.WordSpec
 import org.scalatest.BeforeAndAfterEach
 import java.io.FileReader
 import java.io.FileWriter
 import java.io.File

 class MySuite extends WordSpec with BeforeAndAfterEach {

   private val FileName = "TempFile.txt"
   private var reader: FileReader = _

   // Set up the temp file needed by the test
   override def beforeEach() {
     val writer = new FileWriter(FileName)
     try {
       writer.write("Hello, test!")
     }
     finally {
       writer.close()
     }

     // Create the reader needed by the test
     reader = new FileReader(FileName)
   }

   // Close and delete the temp file
   override def afterEach() {
     reader.close()
     val file = new File(FileName)
     file.delete()
   }

  "A FileReader" must {
     "read in the contents of a file correctly" in {
       var builder = new StringBuilder
       var c = reader.read()
       while (c != -1) {
         builder.append(c.toChar)
         c = reader.read()
       }
       assert(builder.toString === "Hello, test!")
     }
 
     "read in the first character of a file correctly" in {
       assert(reader.read() === 'H')
     }

     "not be required" in {
       assert(1 + 1 === 2)
     }
   }
 }
 

In this example, the instance variable reader is a var, so it can be reinitialized between tests by the beforeEach method.

Although the BeforeAndAfterEach approach should be familiar to the users of most test other frameworks, ScalaTest provides another alternative that also allows you to perform cleanup after each test: overriding withFixture(NoArgTest). To execute each test, Suite's implementation of the runTest method wraps an invocation of the appropriate test method in a no-arg function. runTest passes that test function to the withFixture(NoArgTest) method, which is responsible for actually running the test by invoking the function. Suite's implementation of withFixture(NoArgTest) simply invokes the function, like this:

 // Default implementation
 protected def withFixture(test: NoArgTest) {
   test()
 }
 

The withFixture(NoArgTest) method exists so that you can override it and set a fixture up before, and clean it up after, each test. Thus, the previous temp file example could also be implemented without mixing in BeforeAndAfterEach, like this:

 import org.scalatest.WordSpec
 import org.scalatest.BeforeAndAfterEach
 import java.io.FileReader
 import java.io.FileWriter
 import java.io.File

 class MySuite extends WordSpec {

   private var reader: FileReader = _

   override def withFixture(test: NoArgTest) {

     val FileName = "TempFile.txt"

     // Set up the temp file needed by the test
     val writer = new FileWriter(FileName)
     try {
       writer.write("Hello, test!")
     }
     finally {
       writer.close()
     }

     // Create the reader needed by the test
     reader = new FileReader(FileName)

     try {
       test() // Invoke the test function
     }
     finally {
       // Close and delete the temp file
       reader.close()
       val file = new File(FileName)
       file.delete()
     }
   }

  "A FileReader" must {
     "read in the contents of a file correctly" in {
       var builder = new StringBuilder
       var c = reader.read()
       while (c != -1) {
         builder.append(c.toChar)
         c = reader.read()
       }
       assert(builder.toString === "Hello, test!")
     }
 
     "read in the first character of a file correctly" in {
       assert(reader.read() === 'H')
     }

     "not be required" in {
       assert(1 + 1 === 2)
     }
   }
 }
 

If you prefer to keep your test classes immutable, one final variation is to use the FixtureWordSpec trait from the org.scalatest.fixture package. Tests in an org.scalatest.fixture.FixtureWordSpec can have a fixture object passed in as a parameter. You must indicate the type of the fixture object by defining the Fixture type member and define a withFixture method that takes a one-arg test function. (A FixtureWordSpec has two overloaded withFixture methods, therefore, one that takes a OneArgTest and the other, inherited from Suite, that takes a NoArgTest.) Inside the withFixture(OneArgTest) method, you create the fixture, pass it into the test function, then perform any necessary cleanup after the test function returns. Instead of invoking each test directly, a FixtureWordSpec will pass a function that invokes the code of a test to withFixture(OneArgTest). Your withFixture(OneArgTest) method, therefore, is responsible for actually running the code of the test by invoking the test function. For example, you could pass the temp file reader fixture to each test that needs it by overriding the withFixture(OneArgTest) method of a FixtureWordSpec, like this:

 import org.scalatest.fixture.FixtureWordSpec
 import java.io.FileReader
 import java.io.FileWriter
 import java.io.File
 
 class MySuite extends FixtureWordSpec {

   type FixtureParam = FileReader

   def withFixture(test: OneArgTest) {

     val FileName = "TempFile.txt"

     // Set up the temp file needed by the test
     val writer = new FileWriter(FileName)
     try {
       writer.write("Hello, test!")
     }
     finally {
       writer.close()
     }

     // Create the reader needed by the test
     val reader = new FileReader(FileName)
  
     try {
       // Run the test using the temp file
       test(reader)
     }
     finally {
       // Close and delete the temp file
       reader.close()
       val file = new File(FileName)
       file.delete()
     }
   }
 
  "A FileReader" must {
     "read in the contents of a file correctly" in { reader =>
       var builder = new StringBuilder
       var c = reader.read()
       while (c != -1) {
         builder.append(c.toChar)
         c = reader.read()
       }
       assert(builder.toString === "Hello, test!")
     }
 
     "read in the first character of a file correctly" in { reader =>
       assert(reader.read() === 'H')
     }

     "not be required" in { () =>
       assert(1 + 1 === 2)
     }
   }
 }
 

It is worth noting that the only difference in the test code between the mutable BeforeAndAfterEach approach shown here and the immutable FixtureWordSpec approach shown previously is that two of the FixtureWordSpec's test functions take a FileReader as a parameter via the "reader =>" at the beginning of the function. Otherwise the test code is identical. One benefit of the explicit parameter is that, as demonstrated by the "A FileReader must not be required" test, a FixtureWordSpec test need not take the fixture. So you can have some tests that take a fixture, and others that don't. In this case, the FixtureWordSpec provides documentation indicating which tests use the fixture and which don't, whereas the BeforeAndAfterEach approach does not. (If you have want to combine tests that take different fixture types in the same WordSpec, you can use MultipleFixtureWordSpec.)

If you want to execute code before and after all tests (and nested suites) in a suite, such as you could do with @BeforeClass and @AfterClass annotations in JUnit 4, you can use the beforeAll and afterAll methods of BeforeAndAfterAll. See the documentation for BeforeAndAfterAll for an example.

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 WordSpec, you first place shared tests in behavior functions. These behavior functions will be invoked during the construction phase of any WordSpec that uses them, so that the tests they contain will be registered as tests in that WordSpec. For example, given this stack class:

 import scala.collection.mutable.ListBuffer
 
 class Stack[T] {

   val MAX = 10
   private var buf = new ListBuffer[T]

   def push(o: T) {
     if (!full)
       o +: buf
     else
       throw new IllegalStateException("can't push onto a full stack")
   }

   def pop(): T = {
     if (!empty)
       buf.remove(0)
     else
       throw new IllegalStateException("can't pop an empty stack")
   }

   def peek: T = {
     if (!empty)
       buf(0)
     else
       throw new IllegalStateException("can't pop an empty stack")
   }

   def full: Boolean = buf.size == MAX
   def empty: Boolean = buf.size == 0
   def size = buf.size

   override def toString = buf.mkString("Stack(", ", ", ")")
 }
 

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 your WordSpec 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 the WordSpec that uses them. If they are shared between different WordSpecs, however, you could also define them in a separate trait that is mixed into each WordSpec 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:

 trait StackBehaviors { this: WordSpec =>
 
   def nonEmptyStack(stack: Stack[Int], lastItemAdded: Int) {
 
     "be non-empty" in {
       assert(!stack.empty)
     }  
 
     "return the top item on peek" in {
       assert(stack.peek === lastItemAdded)
     }
   
     "not remove the top item on peek" in {
       val size = stack.size
       assert(stack.peek === lastItemAdded)
       assert(stack.size === size)
     }
   
     "remove the top item on pop" in {
       val size = stack.size
       assert(stack.pop === lastItemAdded)
       assert(stack.size === size - 1)
     }
   }
   
   def nonFullStack(stack: Stack[Int]) {
       
     "not be full" in {
       assert(!stack.full)
     }
       
     "add to the top on push" in {
       val size = stack.size
       stack.push(7)
       assert(stack.size === size + 1)
       assert(stack.peek === 7)
     }
   }
 }
 

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

 behave like nonEmptyStack(stackWithOneItem, lastValuePushed)
 behave like nonFullStack(stackWithOneItem)
 

If you prefer to use an imperative style to change fixtures, for example by mixing in BeforeAndAfterEach and reassigning a stack var in beforeEach, you could write your behavior functions in the context of that var, 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:

 behave like nonEmptyStack // assuming lastValuePushed is also in scope inside nonEmptyStack
 behave like nonFullStack
 

The recommended style, however, is the functional, pass-all-the-needed-values-in style. Here's an example:

 class SharedTestExampleSpec extends WordSpec with StackBehaviors {
 
   // Stack fixture creation methods
   def emptyStack = new Stack[Int]
 
   def fullStack = {
     val stack = new Stack[Int]
     for (i <- 0 until stack.MAX)
       stack.push(i)
     stack
   }
 
   def stackWithOneItem = {
     val stack = new Stack[Int]
     stack.push(9)
     stack
   }
 
   def stackWithOneItemLessThanCapacity = {
     val stack = new Stack[Int]
     for (i <- 1 to 9)
       stack.push(i)
     stack
   }
 
   val lastValuePushed = 9
 
   "A Stack" when {
     "empty" should {
       "be empty" in {
         assert(emptyStack.empty)
       }
 
       "complain on peek" in {
         intercept[IllegalStateException] {
           emptyStack.peek
         }
       }

       "complain on pop" in {
         intercept[IllegalStateException] {
           emptyStack.pop
         }
       }
     }
 
     "it contains one item" should {
       behave like nonEmptyStack(stackWithOneItem, lastValuePushed)
       behave like nonFullStack(stackWithOneItem)
     }

     
     "it contains one item less than capacity" should {
       behave like nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed)
       behave like nonFullStack(stackWithOneItemLessThanCapacity)
     }
 
     "full" should {
       "be full" in {
         assert(fullStack.full)
       }
 
       behave like nonEmptyStack(fullStack, lastValuePushed)
 
       "complain on a push" in {
         intercept[IllegalStateException] {
           fullStack.push(10)
         }
       }
     }
   }
 }
 

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

 scala> (new SharedTestExampleSpec).execute()
 A Stack (when empty) 
 - should be empty
 - should complain on peek
 - should complain on pop
 A Stack (when it contains 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 (when it contains 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 (when 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 FlatSpec is to make sure each invocation of a behavior function is in the context of a different behavior of clause, which will prepend a string to each test name. For example, the following code in a FlatSpec would register a test with the name "A Stack (when empty) should be empty":

   behavior of "A Stack (when empty)"
       
   it should "be empty" in {
     assert(emptyStack.empty)
   }
   // ...
 

Or, using the shorthand notation:

   "A Stack (when empty)" should "be empty" in {
     assert(emptyStack.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 behavior of clause.

Tagging tests

 import org.scalatest.Tag

 object SlowTest extends Tag("com.mycompany.groups.SlowTest")
 object DbTest extends Tag("com.mycompany.groups.DbTest")
 

Given these definitions, you could place WordSpec tests into groups like this:

 import org.scalatest.WordSpec

 class MySuite extends WordSpec {

   "The Scala language" should {

     "add correctly" taggedAs(SlowTest) in {
       val sum = 1 + 1
       assert(sum === 2)
       assert(sum + 2 === 4)
     }

     "subtract correctly" taggedAs(SlowTest, DbTest) in {
       val diff = 4 - 1
       assert(diff === 3)
       assert(diff - 2 === 1)
     }
   }
 }
 

This code marks both tests with the com.mycompany.groups.SlowTest tag, and test "The Scala language should subtract correctly" with the com.mycompany.groups.DbTest tag.

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

Ignored tests

 import org.scalatest.WordSpec
 import scala.collection.mutable.Stack

 class StackSpec extends WordSpec {

   "A Stack" should {

     "pop values in last-in-first-out order" ignore {
       val stack = new Stack[Int]
       stack.push(1)
       stack.push(2)
       assert(stack.pop() === 2)
       assert(stack.pop() === 1)
     }

     "throw NoSuchElementException if an empty stack is popped" in {
       val emptyStack = new Stack[String]
       intercept[NoSuchElementException] {
         emptyStack.pop()
       }
     }
   }
 }
 

If you run this version of StackSpec with:

 scala> (new StackSpec).execute()
 

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

 A Stack
 - should pop values in last-in-first-out order !!! IGNORED !!!
 - should throw NoSuchElementException if an empty stack is popped
 

Informers

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

 import org.scalatest.WordSpec

 class ArithmeticSpec extends WordSpec {

  "The Scala language" should {
     "add correctly" in {
       val sum = 2 + 3
       assert(sum === 5)
       info("addition seems to work")
     }

     "subtract correctly" in {
       val diff = 7 - 2
       assert(diff === 5)
     }
   }
 }
 

If you run this WordSpec from the interpreter, you will see the following message included in the printed report:

 scala> (new ArithmeticSpec).execute()
 The Scala language 
 - should add correctly
   + addition seems to work 
 - should subtract correctly
 

One use case for the Informer is to pass more information about a specification to the reporter. For example, the GivenWhenThen trait provides methods that use the implicit info provided by WordSpec to pass such information to the reporter. Here's an example:

 import org.scalatest.WordSpec
 import org.scalatest.GivenWhenThen
 
 class ArithmeticSpec extends WordSpec with GivenWhenThen {
 
  "The Scala language" should {
 
     "add correctly" in { 
 
       given("two integers")
       val x = 2
       val y = 3
 
       when("they are added")
       val sum = x + y
 
       then("the result is the sum of the two numbers")
       assert(sum === 5)
     }
 
     "subtract correctly" in {
 
       given("two integers")
       val x = 7
       val y = 2
 
       when("one is subtracted from the other")
       val diff = x - y
 
       then("the result is the difference of the two numbers")
       assert(diff === 5)
     }
   }
 }
 

If you run this WordSpec from the interpreter, you will see the following messages included in the printed report:

 scala> (new ArithmeticSpec).execute()
 The Scala language 
 - should add correctly
   + Given two integers 
   + When they are added 
   + Then the result is the sum of the two numbers 
 - should subtract correctly
   + Given two integers 
   + When one is subtracted from the other 
   + Then the result is the difference of the two numbers 
 

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

 import org.scalatest.WordSpec

 class ArithmeticSpec extends WordSpec {

   // Sharing fixture objects via instance variables
   val shared = 5

  "The Scala language" should {
     "add correctly" in {
       val sum = 2 + 3
       assert(sum === shared)
     }

     "subtract correctly" is (pending)
   }
 }
 

If you run this version of ArithmeticSpec with:

 scala> (new ArithmeticSpec).execute()
 

It will run both tests but report that The Scala language should subtract correctly is pending. You'll see:

 The Scala language
 - should add correctly
 - should subtract correctly (pending)
 

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 the pending method does). Thus the body of pending tests are executed up until they throw TestPendingException. The reason for this difference is that it enables your unfinished test to send InfoProvided messages to the reporter before it completes abruptly with TestPendingException, as shown in the previous example on Informers that used the GivenWhenThen trait. For example, the following snippet in a WordSpec:

  "The Scala language" should {
     "add correctly" in { 
       given("two integers")
       when("they are added")
       then("the result is the sum of the two numbers")
       pending
     }
     // ...
 

Would yield the following output when run in the interpreter:

 The Scala language
 - should add correctly (pending)
   + Given two integers 
   + When they are added 
   + Then the result is the sum of the two numbers