Trait that facilitates a “behavior-driven” style of development (BDD), in which tests
are combined with text that specifies the behavior the tests verify.
(In BDD, the word example is usually used instead of test. The word test will not appear
in your code if you use WordSpec
, so if you prefer the word example you can use it. However, in this documentation
the word test will be used, for clarity and to be consistent with the rest of ScalaTest.)
Trait WordSpec
is so named because
you specification text is structured by placing words after strings.
Here's an example WordSpec
:
import org.scalatest.WordSpec import scala.collection.mutable.Stackclass 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.WordSpecclass 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.WordSpecclass 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.WordSpecclass 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.WordSpecclass 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.WordSpecclass 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
.
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
WordSpec
s 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.WordSpecclass 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 var
s
between tests. Before going that route, you should consider some approaches that
avoid var
s. 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.ListBufferclass 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 val
s 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.Fileclass 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.Fileclass 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.Fileclass 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.
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.ListBufferclass 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 WordSpec
s, 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.
A WordSpec
's tests may be classified into groups by tagging them with string names.
As with any suite, when executing a WordSpec
, groups of tests can
optionally be included and/or excluded. To tag a WordSpec
's tests,
you pass objects that extend abstract class org.scalatest.Tag
to taggedAs
method
invoked on the string that describes the test you want to tag. Class Tag
takes one parameter,
a string name. If you have
created Java annotation interfaces for use as group names in direct subclasses of org.scalatest.Suite
,
then you will probably want to use group names on your WordSpec
s that match. To do so, simply
pass the fully qualified names of the Java interfaces to the Tag
constructor. For example, if you've
defined Java annotation interfaces with fully qualified names, com.mycompany.groups.SlowTest
and com.mycompany.groups.DbTest
, then you could
create matching groups for Spec
s like this:
import org.scalatest.Tagobject 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.WordSpecclass 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.
To support the common use case of “temporarily” disabling a test, with the
good intention of resurrecting the test at a later time, WordSpec
adds a method
ignore
to strings that can be used instead of in
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:
import org.scalatest.WordSpec import scala.collection.mutable.Stackclass 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
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.WordSpecclass 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.GivenWhenThenclass 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
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.WordSpecclass 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 Informer
s
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
Class used via an implicit conversion to enable any two objects to be compared with
===
in assertions in tests.
This class supports the syntax of FlatSpec
, WordSpec
, FixtureFlatSpec
,
and FixtureWordSpec
.
This class supports the syntax of FlatSpec
, WordSpec
, FixtureFlatSpec
,
and FixtureWordSpec
.
This class supports the syntax of FlatSpec
, WordSpec
, FixtureFlatSpec
,
and FixtureWordSpec
.
Assert that an Option[String]
is None
.
Assert that an Option[String]
is None
.
If the condition is None
, this method returns normally.
Else, it throws TestFailedException
with the String
value of the Some
included in the TestFailedException
's
detail message.
This form of assert
is usually called in conjunction with an
implicit conversion to Equalizer
, using a ===
comparison, as in:
assert(a === b)
For more information on how this mechanism works, see the documentation for
Equalizer
.
the Option[String]
to assert
Assert that an Option[String]
is None
.
Assert that an Option[String]
is None
.
If the condition is None
, this method returns normally.
Else, it throws TestFailedException
with the String
value of the Some
, as well as the
String
obtained by invoking toString
on the
specified message
,
included in the TestFailedException
's detail message.
This form of assert
is usually called in conjunction with an
implicit conversion to Equalizer
, using a ===
comparison, as in:
assert(a === b, "extra info reported if assertion fails")
For more information on how this mechanism works, see the documentation for
Equalizer
.
the Option[String]
to assert
An objects whose toString
method returns a message to include in a failure report.
Assert that a boolean condition, described in String
message
, is true.
Assert that a boolean condition, described in String
message
, is true.
If the condition is true
, this method returns normally.
Else, it throws TestFailedException
with the
String
obtained by invoking toString
on the
specified message
as the exception's detail message.
the boolean condition to assert
An objects whose toString
method returns a message to include in a failure report.
Assert that a boolean condition is true.
Assert that a boolean condition is true.
If the condition is true
, this method returns normally.
Else, it throws TestFailedException
.
the boolean condition to assert
Implicit conversion from Any
to Equalizer
, used to enable
assertions with ===
comparisons.
Implicit conversion from Any
to Equalizer
, used to enable
assertions with ===
comparisons.
For more information on this mechanism, see the documentation for </code>Equalizer</code>.
Because trait Suite
mixes in Assertions
, this implicit conversion will always be
available by default in ScalaTest Suite
s. This is the only implicit conversion that is in scope by default in every
ScalaTest Suite
. Other implicit conversions offered by ScalaTest, such as those that support the matchers DSL
or invokePrivate
, must be explicitly invited into your test code, either by mixing in a trait or importing the
members of its companion object. The reason ScalaTest requires you to invite in implicit conversions (with the exception of the
implicit conversion for ===
operator) is because if one of ScalaTest's implicit conversions clashes with an
implicit conversion used in the code you are trying to test, your program won't compile. Thus there is a chance that if you
are ever trying to use a library or test some code that also offers an implicit conversion involving a ===
operator,
you could run into the problem of a compiler error due to an ambiguous implicit conversion. If that happens, you can turn off
the implicit conversion offered by this convertToEqualizer
method simply by overriding the method in your
Suite
subclass, but not marking it as implicit:
// In your Suite subclass override def convertToEqualizer(left: Any) = new Equalizer(left)
the object whose type to convert to Equalizer
.
Implicitly converts an object of type String
to a StringCanWrapper
,
to enable can
methods to be invokable on that object.
Implicitly converts an object of type String
to a StringCanWrapper
,
to enable can
methods to be invokable on that object.
Implicitly converts an object of type String
to a StringMustWrapper
,
to enable must
methods to be invokable on that object.
Implicitly converts an object of type String
to a StringMustWrapper
,
to enable must
methods to be invokable on that object.
Implicitly converts an object of type String
to a StringShouldWrapperForVerb
,
to enable should
methods to be invokable on that object.
Implicitly converts an object of type String
to a StringShouldWrapperForVerb
,
to enable should
methods to be invokable on that object.
Executes the test specified as testName
in this Suite
with the specified configMap
, printing
results to the standard output.
Executes the test specified as testName
in this Suite
with the specified configMap
, printing
results to the standard output.
This method implementation calls run
on this Suite
, passing in:
testName
- Some(testName)
reporter
- a reporter that prints to the standard outputstopper
- a Stopper
whose apply
method always returns false
filter
- a Filter
constructed with None
for tagsToInclude
and Set()
for tagsToExclude
configMap
- the specified configMap
Map[String, Any]
distributor
- None
tracker
- a new Tracker
This method serves as a convenient way to execute a single test, passing in some objects via the configMap
, especially from
within the Scala interpreter.
Note: In ScalaTest, the terms "execute" and "run" basically mean the same thing and
can be used interchangably. The reason this convenience method and its three overloaded forms
aren't named run
is described the documentation of the overloaded form that
takes no parameters: execute().
the name of one test to run.
a Map
of key-value pairs that can be used by the executing Suite
of tests.
Executes the test specified as testName
in this Suite
, printing results to the standard output.
Executes the test specified as testName
in this Suite
, printing results to the standard output.
This method implementation calls run
on this Suite
, passing in:
testName
- Some(testName)
reporter
- a reporter that prints to the standard outputstopper
- a Stopper
whose apply
method always returns false
filter
- a Filter
constructed with None
for tagsToInclude
and Set()
for tagsToExclude
configMap
- an empty Map[String, Any]
distributor
- None
tracker
- a new Tracker
This method serves as a convenient way to run a single test, especially from within the Scala interpreter.
Note: In ScalaTest, the terms "execute" and "run" basically mean the same thing and
can be used interchangably. The reason this convenience method and its three overloaded forms
aren't named run
is described the documentation of the overloaded form that
takes no parameters: execute().
the name of one test to run.
Executes this Suite
with the specified configMap
, printing results to the standard output.
Executes this Suite
with the specified configMap
, printing results to the standard output.
This method implementation calls run
on this Suite
, passing in:
testName
- None
reporter
- a reporter that prints to the standard outputstopper
- a Stopper
whose apply
method always returns false
filter
- a Filter
constructed with None
for tagsToInclude
and Set()
for tagsToExclude
configMap
- the specified configMap
Map[String, Any]
distributor
- None
tracker
- a new Tracker
This method serves as a convenient way to execute a Suite
, passing in some objects via the configMap
, especially from within the Scala interpreter.
Note: In ScalaTest, the terms "execute" and "run" basically mean the same thing and
can be used interchangably. The reason this convenience method and its three overloaded forms
aren't named run
is described the documentation of the overloaded form that
takes no parameters: execute().
a Map
of key-value pairs that can be used by the executing Suite
of tests.
Executes this Suite
, printing results to the standard output.
Executes this Suite
, printing results to the standard output.
This method implementation calls run
on this Suite
, passing in:
testName
- None
reporter
- a reporter that prints to the standard outputstopper
- a Stopper
whose apply
method always returns false
filter
- a Filter
constructed with None
for tagsToInclude
and Set()
for tagsToExclude
configMap
- an empty Map[String, Any]
distributor
- None
tracker
- a new Tracker
This method serves as a convenient way to execute a Suite
, especially from
within the Scala interpreter.
Note: In ScalaTest, the terms "execute" and "run" basically mean the same thing and
can be used interchangably. The reason this convenience method and its three overloaded forms
aren't named run
is because junit.framework.TestCase
declares a run
method
that takes no arguments but returns a junit.framework.TestResult
. That
run
method would not overload with this method if it were named run
,
because it would have the same parameters but a different return type than the one
defined in TestCase
. To facilitate integration with JUnit 3, therefore,
these convenience "run" methods are named execute
. In particular, this allows trait
org.scalatest.junit.JUnit3Suite
to extend both org.scalatest.Suite
and
junit.framework.TestCase
, which enables the creating of classes that
can be run with either ScalaTest or JUnit 3.
Expect that the value passed as expected
equals the value passed as actual
.
Expect that the value passed as expected
equals the value passed as actual
.
If the actual
value equals the expected
value
(as determined by ==
), expect
returns
normally. Else, expect
throws an
TestFailedException
whose detail message includes the expected and actual values.
the expected value
the actual value, which should equal the passed expected
value
Expect that the value passed as expected
equals the value passed as actual
.
Expect that the value passed as expected
equals the value passed as actual
.
If the actual
equals the expected
(as determined by ==
), expect
returns
normally. Else, if actual
is not equal to expected
, expect
throws an
TestFailedException
whose detail message includes the expected and actual values, as well as the String
obtained by invoking toString
on the passed message
.
the expected value
An object whose toString
method returns a message to include in a failure report.
the actual value, which should equal the passed expected
value
The total number of tests that are expected to run when this Suite
's run
method is invoked.
The total number of tests that are expected to run when this Suite
's run
method is invoked.
This trait's implementation of this method returns the sum of:
testNames
List
, minus the number of tests marked as ignoredexpectedTestCount
on every nested Suite
contained in
nestedSuites
a Filter
with which to filter tests to count based on their tags
Throws TestFailedException
, with the passed
Throwable
cause, to indicate a test failed.
Throws TestFailedException
, with the passed
Throwable
cause, to indicate a test failed.
The getMessage
method of the thrown TestFailedException
will return cause.toString()
.
a Throwable
that indicates the cause of the failure.
Throws TestFailedException
, with the passed
String
message
as the exception's detail
message and Throwable
cause, to indicate a test failed.
Throws TestFailedException
, with the passed
String
message
as the exception's detail
message and Throwable
cause, to indicate a test failed.
A message describing the failure.
A Throwable
that indicates the cause of the failure.
Throws TestFailedException
, with the passed
String
message
as the exception's detail
message, to indicate a test failed.
Throws TestFailedException
, with the passed
String
message
as the exception's detail
message, to indicate a test failed.
A message describing the failure.
Throws TestFailedException
to indicate a test failed.
Throws TestFailedException
to indicate a test failed.
The groups
methods has been deprecated and will be removed in a future version of ScalaTest.
The groups
methods has been deprecated and will be removed in a future version of ScalaTest.
Please call (and override) tags
instead.
Intercept and return an exception that's expected to be thrown by the passed function value.
Intercept and return an exception that's expected to
be thrown by the passed function value. The thrown exception must be an instance of the
type specified by the type parameter of this method. This method invokes the passed
function. If the function throws an exception that's an instance of the specified type,
this method returns that exception. Else, whether the passed function returns normally
or completes abruptly with a different exception, this method throws TestFailedException
.
Note that the type specified as this method's type parameter may represent any subtype of
AnyRef
, not just Throwable
or one of its subclasses. In
Scala, exceptions can be caught based on traits they implement, so it may at times make sense
to specify a trait that the intercepted exception's class must mix in. If a class instance is
passed for a type that could not possibly be used to catch an exception (such as String
,
for example), this method will complete abruptly with a TestFailedException
.
the function value that should throw the expected exception
an implicit Manifest
representing the type of the specified
type parameter.
the intercepted exception, if it is of the expected type
A List
of this Suite
object's nested Suite
s. If this Suite
contains no nested Suite
s,
this method returns an empty List
. This trait's implementation of this method returns an empty List
.
A List
of this Suite
object's nested Suite
s. If this Suite
contains no nested Suite
s,
this method returns an empty List
. This trait's implementation of this method returns an empty List
.
Throws TestPendingException
to indicate a test is pending.
Throws TestPendingException
to indicate a test is pending.
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.
Note: This method always completes abruptly with a TestPendingException
. Thus it always has a side
effect. Methods with side effects are usually invoked with parentheses, as in pending()
. This
method is defined as a parameterless method, in flagrant contradiction to recommended Scala style, because it
forms a kind of DSL for pending tests. It enables tests in suites such as FunSuite
or Spec
to be denoted by placing "(pending)
" after the test name, as in:
test("that style rules are not laws") (pending)
Readers of the code see "pending" in parentheses, which looks like a little note attached to the test name to indicate
it is pending. Whereas "(pending())
looks more like a method call, "(pending)
" lets readers
stay at a higher level, forgetting how it is implemented and just focusing on the intent of the programmer who wrote the code.
Execute the passed block of code, and if it completes abruptly, throw TestPendingException
, else
throw TestFailedException
.
Execute the passed block of code, and if it completes abruptly, throw TestPendingException
, else
throw TestFailedException
.
This method can be used to temporarily change a failing test into a pending test in such a way that it will
automatically turn back into a failing test once the problem originally causing the test to fail has been fixed.
At that point, you need only remove the pendingUntilFixed
call. In other words, a
pendingUntilFixed
surrounding a block of code that isn't broken is treated as a test failure.
The motivation for this behavior is to encourage people to remove pendingUntilFixed
calls when
there are no longer needed.
This method facilitates a style of testing in which tests are written before the code they test. Sometimes you may
encounter a test failure that requires more functionality than you want to tackle without writing more tests. In this
case you can mark the bit of test code causing the failure with pendingUntilFixed
. You can then write more
tests and functionality that eventually will get your production code to a point where the original test won't fail anymore.
At this point the code block marked with pendingUntilFixed
will no longer throw an exception (because the
problem has been fixed). This will in turn cause pendingUntilFixed
to throw TestFailedException
with a detail message explaining you need to go back and remove the pendingUntilFixed
call as the problem orginally
causing your test code to fail has been fixed.
a block of code, which if it completes abruptly, should trigger a TestPendingException
Runs this suite of tests.
Runs this suite of tests.
If testName
is None
, this trait's implementation of this method
calls these two methods on this object in this order:
runNestedSuites(report, stopper, tagsToInclude, tagsToExclude, configMap, distributor)
runTests(testName, report, stopper, tagsToInclude, tagsToExclude, configMap)
If testName
is defined, then this trait's implementation of this method
calls runTests
, but does not call runNestedSuites
. This behavior
is part of the contract of this method. Subclasses that override run
must take
care not to call runNestedSuites
if testName
is defined. (The
OneInstancePerTest
trait depends on this behavior, for example.)
Subclasses and subtraits that override this run
method can implement them without
invoking either the runTests
or runNestedSuites
methods, which
are invoked by this trait's implementation of this method. It is recommended, but not required,
that subclasses and subtraits that override run
in a way that does not
invoke runNestedSuites
also override runNestedSuites
and make it
final. Similarly it is recommended, but not required,
that subclasses and subtraits that override run
in a way that does not
invoke runTests
also override runTests
(and runTest
,
which this trait's implementation of runTests
calls) and make it
final. The implementation of these final methods can either invoke the superclass implementation
of the method, or throw an UnsupportedOperationException
if appropriate. The
reason for this recommendation is that ScalaTest includes several traits that override
these methods to allow behavior to be mixed into a Suite
. For example, trait
BeforeAndAfterEach
overrides runTests
s. In a Suite
subclass that no longer invokes runTests
from run
, the
BeforeAndAfterEach
trait is not applicable. Mixing it in would have no effect.
By making runTests
final in such a Suite
subtrait, you make
the attempt to mix BeforeAndAfterEach
into a subclass of your subtrait
a compiler error. (It would fail to compile with a complaint that BeforeAndAfterEach
is trying to override runTests
, which is a final method in your trait.)
an optional name of one test to run. If None
, all relevant tests should be run.
I.e., None
acts like a wildcard that means run all relevant tests in this Suite
.
the Reporter
to which results will be reported
the Stopper
that will be consulted to determine whether to stop execution early.
a Filter
with which to filter tests based on their tags
a Map
of key-value pairs that can be used by the executing Suite
of tests.
an optional Distributor
, into which to put nested Suite
s to be run
by another entity, such as concurrently by a pool of threads. If None
, nested Suite
s will be run sequentially.
a Tracker
tracking Ordinal
s being fired by the current thread.
A user-friendly suite name for this Suite
.
A user-friendly suite name for this Suite
.
This trait's
implementation of this method returns the simple name of this object's class. This
trait's implementation of runNestedSuites
calls this method to obtain a
name for Report
s to pass to the suiteStarting
, suiteCompleted
,
and suiteAborted
methods of the Reporter
.
this Suite
object's suite name.
A Map
whose keys are String
tag names to which tests in this Spec
belong, and values
the Set
of test names that belong to each tag. If this WordSpec
contains no tags, this method returns an empty Map
.
A Map
whose keys are String
tag names to which tests in this Spec
belong, and values
the Set
of test names that belong to each tag. If this WordSpec
contains no tags, this method returns an empty Map
.
This trait's implementation returns tags that were passed as strings contained in Tag
objects passed to
methods test
and ignore
.
An immutable Set
of test names. If this WordSpec
contains no tests, this method returns an
empty Set
.
An immutable Set
of test names. If this WordSpec
contains no tests, this method returns an
empty Set
.
This trait's implementation of this method will return a set that contains the names of all registered tests. The set's
iterator will return those names in the order in which the tests were registered. Each test's name is composed
of the concatenation of the text of each surrounding describer, in order from outside in, and the text of the
example itself, with all components separated by a space. For example, consider this WordSpec
:
import org.scalatest.WordSpecclass StackSpec { "A Stack" when { "not empty" must { "allow me to pop" in {} } "not full" must { "allow me to push" in {} } } }
Invoking testNames
on this Spec
will yield a set that contains the following
two test name strings:
"A Stack (when not empty) must allow me to pop" "A Stack (when not full) must allow me to push"
Executes the block of code passed as the second parameter, and, if it
completes abruptly with a ModifiableMessage
exception,
prepends the "clue" string passed as the first parameter to the beginning of the detail message
of that thrown exception, then rethrows it.
Executes the block of code passed as the second parameter, and, if it
completes abruptly with a ModifiableMessage
exception,
prepends the "clue" string passed as the first parameter to the beginning of the detail message
of that thrown exception, then rethrows it. If clue does not end in a white space
character, one space will be added
between it and the existing detail message (unless the detail message is
not defined).
This method allows you to add more information about what went wrong that will be reported when a test fails. Here's an example:
withClue("(Employee's name was: " + employee.name + ")") { intercept[IllegalArgumentException] { employee.getTask(-1) } }
If an invocation of intercept
completed abruptly with an exception, the resulting message would be something like:
(Employee's name was Bob Jones) Expected IllegalArgumentException to be thrown, but no exception was thrown
Trait that facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify. (In BDD, the word example is usually used instead of test. The word test will not appear in your code if you use
WordSpec
, so if you prefer the word example you can use it. However, in this documentation the word test will be used, for clarity and to be consistent with the rest of ScalaTest.) TraitWordSpec
is so named because you specification text is structured by placing words after strings. Here's an exampleWordSpec
:Note: Trait
WordSpec
is in part inspired by classorg.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
, orcan
, and a block. Here are some examples:You can describe a subject in varying situations by using a
when
clause. Awhen
clause follows the subject and precedes a block. In the block after thewhen
, 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: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:Running the above
StackSpec
in the interpreter would yield: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:In such situations you can place
that
clauses inside the verb clause, like this: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, orthat
. For example, in the previousWordSpec
, the word "provide" is repeated at the beginning of each string inside theshould
block. You can factor out this duplication like this:Once you've defined an after word, you can place it after
when
, a verb (should
,must
, orcan
), orthat
. (You can't place one afterin
oris
, the words that introduce a test.) Here's an example that has after words used in all three places:Running the previous
WordSpec
in the Scala interpreter would yield: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 timerun
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 theWordSpec
has entered its ready phase, i.e., afterrun
has been invoked on theWordSpec
, will be met with a thrownTestRegistrationClosedException
. The recommended style of usingWordSpec
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
.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
WordSpec
s with the same approaches suggested forSuite
in its documentation. The same text that appears in the test fixture section ofSuite
's documentation is repeated here, with examples changed fromSuite
toWordSpec
.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
andemptyStack
in the previousStackSpec
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 toshared
is used by multiple test functions: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
andtearDown
for this purpose. In ScalaTest, you can use theBeforeAndAfterEach
trait, which will be described later, to implement an approach similar to JUnit'ssetUp
andtearDown
, however, this approach often involves reassigningvar
s between tests. Before going that route, you should consider some approaches that avoidvar
s. 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: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 simplyval
s and mix in traitOneInstancePerTest
. If you mix inOneInstancePerTest
, each test will be run in its own instance of theWordSpec
, 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 theBeforeAndAfterEach
trait.BeforeAndAfterEach
'sbeforeEach
method will be run before, and itsafterEach
method after, each test (like JUnit'ssetUp
andtearDown
methods, respectively). For example, you could create a temporary file before each test, and delete it afterwords, like this:In this example, the instance variable
reader
is avar
, so it can be reinitialized between tests by thebeforeEach
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: overridingwithFixture(NoArgTest)
. To execute each test,Suite
's implementation of therunTest
method wraps an invocation of the appropriate test method in a no-arg function.runTest
passes that test function to thewithFixture(NoArgTest)
method, which is responsible for actually running the test by invoking the function.Suite
's implementation ofwithFixture(NoArgTest)
simply invokes the function, like this: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 inBeforeAndAfterEach
, like this:If you prefer to keep your test classes immutable, one final variation is to use the
FixtureWordSpec
trait from theorg.scalatest.fixture
package. Tests in anorg.scalatest.fixture.FixtureWordSpec
can have a fixture object passed in as a parameter. You must indicate the type of the fixture object by defining theFixture
type member and define awithFixture
method that takes a one-arg test function. (AFixtureWordSpec
has two overloadedwithFixture
methods, therefore, one that takes aOneArgTest
and the other, inherited fromSuite
, that takes aNoArgTest
.) Inside thewithFixture(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, aFixtureWordSpec
will pass a function that invokes the code of a test towithFixture(OneArgTest)
. YourwithFixture(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 thewithFixture(OneArgTest)
method of aFixtureWordSpec
, like this:It is worth noting that the only difference in the test code between the mutable
BeforeAndAfterEach
approach shown here and the immutableFixtureWordSpec
approach shown previously is that two of theFixtureWordSpec
's test functions take aFileReader
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, aFixtureWordSpec
test need not take the fixture. So you can have some tests that take a fixture, and others that don't. In this case, theFixtureWordSpec
provides documentation indicating which tests use the fixture and which don't, whereas theBeforeAndAfterEach
approach does not. (If you have want to combine tests that take different fixture types in the sameWordSpec
, 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 thebeforeAll
andafterAll
methods ofBeforeAndAfterAll
. See the documentation forBeforeAndAfterAll
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 anyWordSpec
that uses them, so that the tests they contain will be registered as tests in thatWordSpec
. 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 yourWordSpec
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 theWordSpec
that uses them. If they are shared between differentWordSpec
s, however, you could also define them in a separate trait that is mixed into eachWordSpec
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
WordSpec
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:
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 differentbehavior of
clause, which will prepend a string to each test name. For example, the following code in aFlatSpec
would register a test with the name"A Stack (when empty) should be empty"
:Or, using the shorthand notation:
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 differentbehavior of
clause.Tagging tests
A
WordSpec
's tests may be classified into groups by tagging them with string names. As with any suite, when executing aWordSpec
, groups of tests can optionally be included and/or excluded. To tag aWordSpec
's tests, you pass objects that extend abstract classorg.scalatest.Tag
totaggedAs
method invoked on the string that describes the test you want to tag. ClassTag
takes one parameter, a string name. If you have created Java annotation interfaces for use as group names in direct subclasses oforg.scalatest.Suite
, then you will probably want to use group names on yourWordSpec
s that match. To do so, simply pass the fully qualified names of the Java interfaces to theTag
constructor. For example, if you've defined Java annotation interfaces with fully qualified names,com.mycompany.groups.SlowTest
andcom.mycompany.groups.DbTest
, then you could create matching groups forSpec
s like this:Given these definitions, you could place
WordSpec
tests into groups like this:This code marks both tests with the
com.mycompany.groups.SlowTest
tag, and test"The Scala language should subtract correctly"
with thecom.mycompany.groups.DbTest
tag.The primary
run
method takes aFilter
, whose constructor takes an optionalSet[String]
s 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.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,
WordSpec
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
StackSpec
with:It will run only the second test and report that the first test was ignored:
Informers
One of the parameters to the primary
run
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 byWordSpec
'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. Here's an example:If you run this
WordSpec
from the interpreter, you will see the following message included in the printed report: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 byWordSpec
to pass such information to the reporter. Here's an example:If you run this
WordSpec
from the interpreter, you will see the following messages included in the printed report: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 withTestPendingException
. Because tests in ScalaTest can be designated as pending withTestPendingException
, 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 aWordSpec
like this:If you run this version of
ArithmeticSpec
with:It will run both tests but report that
The Scala language should subtract correctly
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 aWordSpec
:Would yield the following output when run in the interpreter: