org.scalatest.wordspec.AnyWordSpec.scala Maven / Gradle / Ivy
/*
* Copyright 2001-2019 Artima, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.scalatest.wordspec
import org.scalatest.{ Suite, Finders }
/**
* Facilitates a “behavior-driven” style of development (BDD), in which tests
* are combined with text that specifies the behavior the tests verify.
*
*
* Recommended Usage:
* For teams coming from specs or specs2, AnyWordSpec will feel familiar, and is often the most natural way to port specsN tests to
* ScalaTest. AnyWordSpec is very prescriptive in how text must be written, so a good fit for teams who want a high degree of discipline
* enforced upon their specification text.
*
*
*
* Class AnyWordSpec is so named because your specification text is structured by placing words after strings.
* Here's an example AnyWordSpec:
*
*
*
* package org.scalatest.examples.wordspec
*
* import org.scalatest._
*
* class SetSpec extends wordspec.AnyWordSpec {
*
* "A Set" when {
* "empty" should {
* "have size 0" in {
* assert(Set.empty.size === 0)
* }
*
* "produce NoSuchElementException when head is invoked" in {
* assertThrows[NoSuchElementException] {
* Set.empty.head
* }
* }
* }
* }
* }
*
*
*
* In a AnyWordSpec 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._
*
* class StackSpec extends wordspec.AnyWordSpec {
* "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> org.scalatest.run(new StackSpec)
* StackSpec:
* A Stack
* when empty
* - should be empty
* - should complain on peek
* - should complain on pop
* 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 AnyWordSpec code is nested, which can help you eliminate any repeated phrases
* in the specification portion of your code, the output printed moves when and should
* down to the beginning of the next line.
*
*
*
* 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, which" is repeated:
*
*
*
* import org.scalatest._
*
* class AndOrSpec extends wordspec.AnyWordSpec {
*
* "The ScalaTest Matchers DSL" should {
* "provide an and operator, which returns silently when evaluating true and true" in {}
* "provide an and operator, which throws a TestFailedException when evaluating true and false" in {}
* "provide an and operator, which throws a TestFailedException when evaluating false and true" in {}
* "provide an and operator, which throws a TestFailedException when evaluating false and false" in {}
* "provide an or operator, which returns silently when evaluating true or true" in {}
* "provide an or operator, which returns silently when evaluating true or false" in {}
* "provide an or operator, which returns silently when evaluating false or true" in {}
* "provide an or operator, which throws a TestFailedException when evaluating false or false" in {}
* }
* }
*
*
*
* In such situations you can place which clauses inside the verb clause, like this:
*
*
*
* import org.scalatest._
*
* class AndOrSpec extends wordspec.AnyWordSpec {
*
* "The ScalaTest Matchers DSL" should {
* "provide an and operator," which {
* "returns silently when evaluating true and true" in {}
* "throws a TestFailedException when evaluating true and false" in {}
* "throws a TestFailedException when evaluating false and true" in {}
* "throws a TestFailedException when evaluating false and false" in {}
* }
* "provide an or operator," which {
* "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 {}
* }
* }
* }
*
*
*
* Running the above AndOrSpec in the interpreter would yield:
*
*
*
* scala> org.scalatest.run(new AndOrSpec)
* AndOrSpec:
* The ScalaTest Matchers DSL
* should provide an and operator, which
* - returns silently when evaluating true and true
* - throws a TestFailedException when evaluating true and false
* - throws a TestFailedException when evaluating false and true
* - throws a TestFailedException when evaluating false and false
* should provide an or operator, which
* - returns silently when evaluating true or true
* - returns silently when evaluating true or false
* - returns silently when evaluating false or true
* - throws a TestFailedException when evaluating false or false
*
*
*
* Note that unlike when and should/must/can, a which appears
* in the output right where you put it in the input, at the end of the line, to maximize readability.
*
*
*
* 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
* which. For example, in the previous AnyWordSpec, 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._
*
* class AndOrSpec extends wordspec.AnyWordSpec {
*
* def provide = afterWord("provide")
*
* "The ScalaTest Matchers DSL" should provide {
* "an and operator," which {
* "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," which {
* "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 {}
* }
* }
* }
*
*
*
* Running the above version of AndOrSpec with the provide after word in the interpreter would give you:
*
*
*
* scala> org.scalatest.run(new AndOrSpec)
* AndOrSpec:
* The ScalaTest Matchers DSL
* should provide
* an and operator, which
* - returns silently when evaluating true and true
* - throws a TestFailedException when evaluating true and false
* - that throws a TestFailedException when evaluating false and true
* - throws a TestFailedException when evaluating false and false
* an or operator, which
* - returns silently when evaluating true or true
* - returns silently when evaluating true or false
* - returns silently when evaluating false or true
* - throws a TestFailedException when evaluating false or false
*
*
*
* Once you've defined an after word, you can place it after when, a verb
* (should, must, or can), or
* which. (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._
*
* class ScalaTestGUISpec extends wordspec.AnyWordSpec {
*
* 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," which is {
* "enabled if the clicked-on event is rerunnable" in {}
* "disabled if the clicked-on event is not rerunnable" in {}
* }
* }
* }
* }
*
*
*
* Running the previous AnyWordSpec in the Scala interpreter would yield:
*
*
*
* scala> org.scalatest.run(new ScalaTestGUISpec)
* ScalaTestGUISpec:
* 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
* - the details for the event in the details area
* a rerun button, which is
* - enabled if the clicked-on event is rerunnable
* - disabled if the clicked-on event is not rerunnable
*
*
*
* In case when you need to use different verb for a same subject, you can use it or they shorthand to avoid subject duplication:
*
*
*
* "A Stack" when {
* // ...
* }
*
* it should {
* // ...
* }
*
*
*
* A AnyWordSpec'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 AnyWordSpec is
* in its registration phase. Any attempt to register a test after the AnyWordSpec has
* entered its ready phase, i.e., after run has been invoked on the AnyWordSpec,
* will be met with a thrown TestRegistrationClosedException. The recommended style
* of using AnyWordSpec 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.
*
*
*
* Note: Class AnyWordSpec is in part inspired by class org.specs.Specification, designed by
* Eric Torreborre for the specs framework.
*
*
* Ignored tests
*
*
* To support the common use case of temporarily disabling a test, with the
* good intention of resurrecting the test at a later time, AnyWordSpec 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:
*
*
*
* package org.scalatest.examples.wordspec.ignore
*
* import org.scalatest._
*
* class SetSpec extends wordspec.AnyWordSpec {
*
* "A Set" when {
* "empty" should {
* "have size 0" ignore {
* assert(Set.empty.size === 0)
* }
*
* "produce NoSuchElementException when head is invoked" in {
* assertThrows[NoSuchElementException] {
* Set.empty.head
* }
* }
* }
* }
* }
*
*
*
* If you run this version of SetSpec with:
*
*
*
* scala> org.scalatest.run(new SetSpec)
*
*
*
* It will run only the second test and report that the first test was ignored:
*
*
*
* A Set
* when empty
* - should have size 0 !!! IGNORED !!!
* - should should produce NoSuchElementException when head is invoked
*
*
*
* If you wish to temporarily ignore an entire suite of tests, you can (on the JVM, not Scala.js) annotate the test class with @Ignore, like this:
*
*
*
* package org.scalatest.examples.wordspec.ignoreall
*
* import org.scalatest._
*
* @Ignore
* class SetSpec extends wordspec.AnyWordSpec {
*
* "A Set" when {
* "empty" should {
* "have size 0" in {
* assert(Set.empty.size === 0)
* }
*
* "produce NoSuchElementException when head is invoked" in {
* assertThrows[NoSuchElementException] {
* Set.empty.head
* }
* }
* }
* }
* }
*
*
*
* When you mark a test class with a tag annotation, ScalaTest will mark each test defined in that class with that tag.
* Thus, marking the SetSpec in the above example with the @Ignore tag annotation means that both tests
* in the class will be ignored. If you run the above SetSpec in the Scala interpreter, you'll see:
*
*
*
* scala> org.scalatest.run(new SetSpec)
* SetSpec:
* A Set
* when empty
* - should have size 0 !!! IGNORED !!!
* - should produce NoSuchElementException when head is invoked !!! IGNORED !!!
*
*
*
* Note that marking a test class as ignored won't prevent it from being discovered by ScalaTest. Ignored classes
* will be discovered and run, and all their tests will be reported as ignored. This is intended to keep the ignored
* class visible, to encourage the developers to eventually fix and “un-ignore” it. If you want to
* prevent a class from being discovered at all (on the JVM, not Scala.js), use the DoNotDiscover annotation instead.
*
*
* Informers
*
*
* One of the parameters to AnyWordSpec's 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 AnyWordSpec'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.
*
*
*
* 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:
*
*
*
* package org.scalatest.examples.wordspec.info
*
* import collection.mutable
* import org.scalatest._
*
* class SetSpec extends wordspec.AnyWordSpec with GivenWhenThen {
*
* "A mutable Set" should {
* "allow an element to be added" in {
* Given("an empty mutable Set")
* val set = mutable.Set.empty[String]
*
* When("an element is added")
* set += "clarity"
*
* Then("the Set should have size 1")
* assert(set.size === 1)
*
* And("the Set should contain the added element")
* assert(set.contains("clarity"))
*
* info("That's all folks!")
* }
* }
* }
*
*
*
* If you run this AnyWordSpec from the interpreter, you will see the following output:
*
*
*
* scala> org.scalatest.run(new SetSpec)
* A mutable Set
* - should allow an element to be added
* + Given an empty mutable Set
* + When an element is added
* + Then the Set should have size 1
* + And the Set should contain the added element
* + That's all folks!
*
*
* Documenters
*
*
* AnyWordSpec also provides a markup method that returns a Documenter, which allows you to send
* to the Reporter text formatted in Markdown syntax.
* You can pass the extra information to the Documenter via its apply method.
* The Documenter will then pass the information to the Reporter via an MarkupProvided event.
*
*
*
* Here's an example AnyWordSpec that uses markup:
*
*
*
* package org.scalatest.examples.wordspec.markup
*
* import collection.mutable
* import org.scalatest._
*
* class SetSpec extends wordspec.AnyWordSpec with GivenWhenThen {
*
* markup { """
*
* Mutable Set
* -----------
*
* A set is a collection that contains no duplicate elements.
*
* To implement a concrete mutable set, you need to provide implementations
* of the following methods:
*
* def contains(elem: A): Boolean
* def iterator: Iterator[A]
* def += (elem: A): this.type
* def -= (elem: A): this.type
*
* If you wish that methods like `take`,
* `drop`, `filter` return the same kind of set,
* you should also override:
*
* def empty: This
*
* It is also good idea to override methods `foreach` and
* `size` for efficiency.
*
* """ }
*
* "A mutable Set" should {
* "allow an element to be added" in {
* Given("an empty mutable Set")
* val set = mutable.Set.empty[String]
*
* When("an element is added")
* set += "clarity"
*
* Then("the Set should have size 1")
* assert(set.size === 1)
*
* And("the Set should contain the added element")
* assert(set.contains("clarity"))
*
* markup("This test finished with a **bold** statement!")
* }
* }
* }
*
*
*
* Although all of ScalaTest's built-in reporters will display the markup text in some form,
* the HTML reporter will format the markup information into HTML. Thus, the main purpose of markup is to
* add nicely formatted text to HTML reports. Here's what the above SetSpec would look like in the HTML reporter:
*
*
* 
*
* Notifiers and alerters
*
*
* ScalaTest records text passed to info and markup during tests, and sends the recorded text in the recordedEvents field of
* test completion events like TestSucceeded and TestFailed. This allows string reporters (like the standard out reporter) to show
* info and markup text after the test name in a color determined by the outcome of the test. For example, if the test fails, string
* reporters will show the info and markup text in red. If a test succeeds, string reporters will show the info
* and markup text in green. While this approach helps the readability of reports, it means that you can't use info to get status
* updates from long running tests.
*
*
*
* To get immediate (i.e., non-recorded) notifications from tests, you can use note (a Notifier) and alert
* (an Alerter). Here's an example showing the differences:
*
*
*
* package org.scalatest.examples.wordspec.note
*
* import collection.mutable
* import org.scalatest._
*
* class SetSpec extends wordspec.AnyWordSpec {
*
* "A mutable Set" should {
* "allow an element to be added" in {
*
* info("info is recorded")
* markup("markup is *also* recorded")
* note("notes are sent immediately")
* alert("alerts are also sent immediately")
*
* val set = mutable.Set.empty[String]
* set += "clarity"
* assert(set.size === 1)
* assert(set.contains("clarity"))
* }
* }
* }
*
*
*
* Because note and alert information is sent immediately, it will appear before the test name in string reporters, and its color will
* be unrelated to the ultimate outcome of the test: note text will always appear in green, alert text will always appear in yellow.
* Here's an example:
*
*
*
* scala> org.scalatest.run(new SetSpec)
* SetSpec:
* A mutable Set
* + notes are sent immediately
* + alerts are also sent immediately
* - should allow an element to be added
* + info is recorded
* + markup is *also* recorded
*
*
*
* Another example is slowpoke notifications.
* If you find a test is taking a long time to complete, but you're not sure which test, you can enable
* slowpoke notifications. ScalaTest will use an Alerter to fire an event whenever a test has been running
* longer than a specified amount of time.
*
*
*
* In summary, use info and markup for text that should form part of the specification output. Use
* note and alert to send status notifications. (Because the HTML reporter is intended to produce a
* readable, printable specification, info and markup text will appear in the HTML report, but
* note and alert text will not.)
*
*
* Pending tests
*
*
* A pending test is one that has been given a name but is not yet implemented. The purpose of
* pending tests is to facilitate a style of testing in which documentation of behavior is sketched
* out before tests are written to verify that behavior (and often, before the behavior of
* the system being tested is itself implemented). Such sketches form a kind of specification of
* what tests and functionality to implement later.
*
*
*
* To support this style of testing, a test can be given a name that specifies one
* bit of behavior required by the system being tested. The test can also include some code that
* sends more information about the behavior to the reporter when the tests run. At the end of the test,
* it can call method pending, which will cause it to complete abruptly 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 AnyWordSpec like this:
*
*
*
* package org.scalatest.examples.wordspec.pending
*
* import org.scalatest._
*
* class SetSpec extends wordspec.AnyWordSpec {
*
* "A Set" when {
* "empty" should {
* "have size 0" in (pending)
*
* "produce NoSuchElementException when head is invoked" in {
* assertThrows[NoSuchElementException] {
* Set.empty.head
* }
* }
* }
* }
* }
*
*
*
* If you run this version of SetSpec with:
*
*
*
* scala> org.scalatest.run(new SetSpec)
*
*
*
* It will run both tests but report that should have size 0 is pending. You'll see:
*
*
*
* A Set
* when empty
* - should have size 0 (pending)
* - should produce NoSuchElementException when head is invoked
*
*
*
* 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
*
*
* Tagging tests
*
* A AnyWordSpec's tests may be classified into groups by tagging them with string names.
* As with any suite, when executing a AnyWordSpec, groups of tests can
* optionally be included and/or excluded. To tag a AnyWordSpec's tests,
* you pass objects that extend class org.scalatest.Tag to methods
* that register tests. Class Tag takes one parameter, a string name. If you have
* created tag annotation interfaces as described in the Tag documentation, then you
* will probably want to use tag names on your test functions that match. To do so, simply
* pass the fully qualified names of the tag interfaces to the Tag constructor. For example, if you've
* defined a tag annotation interface with fully qualified name,
* com.mycompany.tags.DbTest, then you could
* create a matching tag for AnyWordSpecs like this:
*
*
*
* package org.scalatest.examples.wordspec.tagging
*
* import org.scalatest.Tag
*
* object DbTest extends Tag("com.mycompany.tags.DbTest")
*
*
*
* Given these definitions, you could place AnyWordSpec tests into groups with tags like this:
*
*
*
* import org.scalatest._
* import org.scalatest.tagobjects.Slow
*
* class SetSpec extends wordspec.AnyWordSpec {
*
* "A Set" when {
* "empty" should {
* "have size 0" taggedAs(Slow) in {
* assert(Set.empty.size === 0)
* }
*
* "produce NoSuchElementException when head is invoked" taggedAs(Slow, DbTest) in {
* assertThrows[NoSuchElementException] {
* Set.empty.head
* }
* }
* }
* }
* }
*
*
*
* This code marks both tests with the org.scalatest.tags.Slow tag,
* and the second test with the com.mycompany.tags.DbTest tag.
*
*
*
* The run method takes a Filter, whose constructor takes an optional
* Set[String] 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.
*
*
*
* It is recommended, though not required, that you create a corresponding tag annotation when you
* create a Tag object. A tag annotation (on the JVM, not Scala.js) allows you to tag all the tests of a WordSpec in
* one stroke by annotating the class. For more information and examples, see the
* documentation for class Tag. On Scala.js, to tag all tests of a suite, you'll need to
* tag each test individually at the test site.
*
*
*
* Shared fixtures
*
*
* A test fixture is composed of the objects and other artifacts (files, sockets, database
* connections, etc.) tests use to do their work.
* When multiple tests need to work with the same fixtures, it is important to try and avoid
* duplicating the fixture code across those tests. The more code duplication you have in your
* tests, the greater drag the tests will have on refactoring the actual production code.
*
*
*
* ScalaTest recommends three techniques to eliminate such code duplication:
*
*
*
* - Refactor using Scala
* - Override
withFixture
* - Mix in a before-and-after trait
*
*
* Each technique is geared towards helping you reduce code duplication without introducing
* instance vars, shared mutable objects, or other dependencies between tests. Eliminating shared
* mutable state across tests will make your test code easier to reason about and more amenable for parallel
* test execution.
The following sections
* describe these techniques, including explaining the recommended usage
* for each. But first, here's a table summarizing the options:
*
*
*
*
*
* Refactor using Scala when different tests need different fixtures.
*
*
*
*
*
* get-fixture methods
*
*
* The extract method refactor helps you create a fresh instances of mutable fixture objects in each test
* that needs them, but doesn't help you clean them up when you're done.
*
*
*
*
*
* fixture-context objects
*
*
* By placing fixture methods and fields into traits, you can easily give each test just the newly created
* fixtures it needs by mixing together traits. Use this technique when you need different combinations
* of mutable fixture objects in different tests, and don't need to clean up after.
*
*
*
*
*
* loan-fixture methods
*
*
* Factor out dupicate code with the loan pattern when different tests need different fixtures that must be cleaned up afterwards.
*
*
*
*
*
* Override withFixture when most or all tests need the same fixture.
*
*
*
*
*
*
* withFixture(NoArgTest)
*
*
*
* The recommended default approach when most or all tests need the same fixture treatment. This general technique
* allows you, for example, to perform side effects at the beginning and end of all or most tests,
* transform the outcome of tests, retry tests, make decisions based on test names, tags, or other test data.
* Use this technique unless:
*
*
* - Different tests need different fixtures (refactor using Scala instead)
* - An exception in fixture code should abort the suite, not fail the test (use a before-and-after trait instead)
* - You have objects to pass into tests (override
withFixture(OneArgTest) instead)
*
*
*
*
*
*
*
* withFixture(OneArgTest)
*
*
*
* Use when you want to pass the same fixture object or objects as a parameter into all or most tests.
*
*
*
*
*
* Mix in a before-and-after trait when you want an aborted suite, not a failed test, if the fixture code fails.
*
*
*
*
*
* BeforeAndAfter
*
*
* Use this boilerplate-buster when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
*
*
*
*
*
* BeforeAndAfterEach
*
*
* Use when you want to stack traits that perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
*
*
*
*
*
*
* Calling get-fixture methods
*
*
* If you need to create the same mutable fixture objects in multiple tests, and don't need to clean them up after using them, the simplest approach is to write one or
* more get-fixture methods. A get-fixture method returns a new instance of a needed fixture object (or an holder object containing
* multiple fixture objects) each time it is called. You can call a get-fixture method at the beginning of each
* test that needs the fixture, storing the returned object or objects in local variables. Here's an example:
*
*
*
* package org.scalatest.examples.wordspec.getfixture
*
* import org.scalatest._
* import collection.mutable.ListBuffer
*
* class ExampleSpec extends wordspec.AnyWordSpec {
*
* class Fixture {
* val builder = new StringBuilder("ScalaTest is ")
* val buffer = new ListBuffer[String]
* }
*
* def fixture = new Fixture
*
* "Testing" should {
* "be easy" in {
* val f = fixture
* f.builder.append("easy!")
* assert(f.builder.toString === "ScalaTest is easy!")
* assert(f.buffer.isEmpty)
* f.buffer += "sweet"
* }
*
* "be fun" in {
* val f = fixture
* f.builder.append("fun!")
* assert(f.builder.toString === "ScalaTest is fun!")
* assert(f.buffer.isEmpty)
* }
* }
* }
*
*
*
* The “f.” in front of each use of a fixture object provides a visual indication of which objects
* are part of the fixture, but if you prefer, you can import the the members with “import f._” and use the names directly.
*
*
*
* If you need to configure fixture objects differently in different tests, you can pass configuration into the get-fixture method. For example, you could pass
* in an initial value for a mutable fixture object as a parameter to the get-fixture method.
*
*
*
* Instantiating fixture-context objects
*
*
* An alternate technique that is especially useful when different tests need different combinations of fixture objects is to define the fixture objects as instance variables
* of fixture-context objects whose instantiation forms the body of tests. Like get-fixture methods, fixture-context objects are only
* appropriate if you don't need to clean up the fixtures after using them.
*
*
* To use this technique, you define instance variables intialized with fixture objects in traits and/or classes, then in each test instantiate an object that
* contains just the fixture objects needed by the test. Traits allow you to mix together just the fixture objects needed by each test, whereas classes
* allow you to pass data in via a constructor to configure the fixture objects. Here's an example in which fixture objects are partitioned into two traits
* and each test just mixes together the traits it needs:
*
*
*
* package org.scalatest.examples.wordspec.fixturecontext
*
* import collection.mutable.ListBuffer
* import org.scalatest._
*
* class ExampleSpec extends wordspec.AnyWordSpec {
*
* trait Builder {
* val builder = new StringBuilder("ScalaTest is ")
* }
*
* trait Buffer {
* val buffer = ListBuffer("ScalaTest", "is")
* }
*
* "Testing" should {
* // This test needs the StringBuilder fixture
* "be productive" in new Builder {
* builder.append("productive!")
* assert(builder.toString === "ScalaTest is productive!")
* }
* }
*
* "Test code" should {
* // This test needs the ListBuffer[String] fixture
* "be readable" in new Buffer {
* buffer += ("readable!")
* assert(buffer === List("ScalaTest", "is", "readable!"))
* }
*
* // This test needs both the StringBuilder and ListBuffer
* "be clear and concise" in new Builder with Buffer {
* builder.append("clear!")
* buffer += ("concise!")
* assert(builder.toString === "ScalaTest is clear!")
* assert(buffer === List("ScalaTest", "is", "concise!"))
* }
* }
* }
*
*
*
* Overriding withFixture(NoArgTest)
*
*
* Although the get-fixture method and fixture-context object approaches take care of setting up a fixture at the beginning of each
* test, they don't address the problem of cleaning up a fixture at the end of the test. If you just need to perform a side-effect at the beginning or end of
* a test, and don't need to actually pass any fixture objects into the test, you can override withFixture(NoArgTest), one of ScalaTest's
* lifecycle methods defined in trait Suite.
*
*
*
* Trait Suite's implementation of runTest passes a no-arg test function to withFixture(NoArgTest). It is withFixture's
* responsibility to invoke that test function. Suite's implementation of withFixture simply
* invokes the function, like this:
*
*
*
* // Default implementation in trait Suite
* protected def withFixture(test: NoArgTest) = {
* test()
* }
*
*
*
* You can, therefore, override withFixture to perform setup before and/or cleanup after invoking the test function. If
* you have cleanup to perform, you should invoke the test function inside a try block and perform the cleanup in
* a finally clause, in case an exception propagates back through withFixture. (If a test fails because of an exception,
* the test function invoked by withFixture will result in a [[org.scalatest.Failed Failed]] wrapping the exception. Nevertheless,
* best practice is to perform cleanup in a finally clause just in case an exception occurs.)
*
*
*
* The withFixture method is designed to be stacked, and to enable this, you should always call the super implementation
* of withFixture, and let it invoke the test function rather than invoking the test function directly. Instead of writing
* “test()”, you should write “super.withFixture(test)”, like this:
*
*
*
* // Your implementation
* override def withFixture(test: NoArgTest) = {
* // Perform setup
* try super.withFixture(test) // Invoke the test function
* finally {
* // Perform cleanup
* }
* }
*
*
*
* Here's an example in which withFixture(NoArgTest) is used to take a snapshot of the working directory if a test fails, and
* send that information to the reporter:
*
*
*
* package org.scalatest.examples.wordspec.noargtest
*
* import java.io.File
* import org.scalatest._
*
* class ExampleSpec extends wordspec.AnyWordSpec {
*
* override def withFixture(test: NoArgTest) = {
*
* super.withFixture(test) match {
* case failed: Failed =>
* val currDir = new File(".")
* val fileNames = currDir.list()
* info("Dir snapshot: " + fileNames.mkString(", "))
* failed
* case other => other
* }
* }
*
* "This test" should {
* "succeed" in {
* assert(1 + 1 === 2)
* }
*
* "fail" in {
* assert(1 + 1 === 3)
* }
* }
* }
*
*
*
* Running this version of ExampleSuite in the interpreter in a directory with two files, hello.txt and world.txt
* would give the following output:
*
*
*
* scala> org.scalatest.run(new ExampleSuite)
* ExampleSuite:
* This test
* - should succeed
* - should fail *** FAILED ***
* 2 did not equal 3 (:33)
* + Dir snapshot: hello.txt, world.txt
*
*
*
* Note that the NoArgTest passed to withFixture, in addition to
* an apply method that executes the test, also includes the test name and the config
* map passed to runTest. Thus you can also use the test name and configuration objects in your withFixture
* implementation.
*
*
*
* Calling loan-fixture methods
*
*
* If you need to both pass a fixture object into a test and perform cleanup at the end of the test, you'll need to use the loan pattern.
* If different tests need different fixtures that require cleanup, you can implement the loan pattern directly by writing loan-fixture methods.
* A loan-fixture method takes a function whose body forms part or all of a test's code. It creates a fixture, passes it to the test code by invoking the
* function, then cleans up the fixture after the function returns.
*
*
*
* The following example shows three tests that use two fixtures, a database and a file. Both require cleanup after, so each is provided via a
* loan-fixture method. (In this example, the database is simulated with a StringBuffer.)
*
*
*
* import java.util.concurrent.ConcurrentHashMap
*
* object DbServer { // Simulating a database server
* type Db = StringBuffer
* private val databases = new ConcurrentHashMap[String, Db]
* def createDb(name: String): Db = {
* val db = new StringBuffer
* databases.put(name, db)
* db
* }
* def removeDb(name: String) {
* databases.remove(name)
* }
* }
*
* import org.scalatest._
* import DbServer._
* import java.util.UUID.randomUUID
* import java.io._
*
* class ExampleSpec extends wordspec.AnyWordSpec {
*
* def withDatabase(testCode: Db => Any) {
* val dbName = randomUUID.toString
* val db = createDb(dbName) // create the fixture
* try {
* db.append("ScalaTest is ") // perform setup
* testCode(db) // "loan" the fixture to the test
* }
* finally removeDb(dbName) // clean up the fixture
* }
*
* def withFile(testCode: (File, FileWriter) => Any) {
* val file = File.createTempFile("hello", "world") // create the fixture
* val writer = new FileWriter(file)
* try {
* writer.write("ScalaTest is ") // set up the fixture
* testCode(file, writer) // "loan" the fixture to the test
* }
* finally writer.close() // clean up the fixture
* }
*
* "Testing" should {
* // This test needs the file fixture
* "be productive" in withFile { (file, writer) =>
* writer.write("productive!")
* writer.flush()
* assert(file.length === 24)
* }
* }
*
* "Test code" should {
* // This test needs the database fixture
* "be readable" in withDatabase { db =>
* db.append("readable!")
* assert(db.toString === "ScalaTest is readable!")
* }
*
* // This test needs both the file and the database
* "be clear and concise" in withDatabase { db =>
* withFile { (file, writer) => // loan-fixture methods compose
* db.append("clear!")
* writer.write("concise!")
* writer.flush()
* assert(db.toString === "ScalaTest is clear!")
* assert(file.length === 21)
* }
* }
* }
* }
*
*
*
* As demonstrated by the last test, loan-fixture methods compose. Not only do loan-fixture methods allow you to
* give each test the fixture it needs, they allow you to give a test multiple fixtures and clean everything up afterwards.
*
*
*
* Also demonstrated in this example is the technique of giving each test its own "fixture sandbox" to play in. When your fixtures
* involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is
* done in this example. This keeps tests completely isolated, allowing you to run them in parallel if desired.
*
*
*
* Overriding withFixture(OneArgTest)
*
*
* If all or most tests need the same fixture, you can avoid some of the boilerplate of the loan-fixture method approach by using a fixture.WordSpec
* and overriding withFixture(OneArgTest).
* Each test in a FixtureAnyWordSpec takes a fixture as a parameter, allowing you to pass the fixture into
* the test. You must indicate the type of the fixture parameter by specifying FixtureParam, and implement a
* withFixture method that takes a OneArgTest. This withFixture method is responsible for
* invoking the one-arg test function, so you can perform fixture set up before, and clean up after, invoking and passing
* the fixture into the test function.
*
*
*
* To enable the stacking of traits that define withFixture(NoArgTest), it is a good idea to let
* withFixture(NoArgTest) invoke the test function instead of invoking the test
* function directly. To do so, you'll need to convert the OneArgTest to a NoArgTest. You can do that by passing
* the fixture object to the toNoArgTest method of OneArgTest. Instead of
* writing “test(theFixture)”, you'd delegate responsibility for
* invoking the test function to the withFixture(NoArgTest) method of the same instance by writing:
*
*
*
* withFixture(test.toNoArgTest(theFixture))
*
*
*
* Here's a complete example:
*
*
*
* package org.scalatest.examples.wordspec.oneargtest
*
* import org.scalatest.wordspec
* import java.io._
*
* class ExampleSpec extends wordspec.FixtureAnyWordSpec {
*
* case class FixtureParam(file: File, writer: FileWriter)
*
* def withFixture(test: OneArgTest) = {
* val file = File.createTempFile("hello", "world") // create the fixture
* val writer = new FileWriter(file)
* val theFixture = FixtureParam(file, writer)
*
* try {
* writer.write("ScalaTest is ") // set up the fixture
* withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test
* }
* finally writer.close() // clean up the fixture
* }
*
* "Testing" should {
* "be easy" in { f =>
* f.writer.write("easy!")
* f.writer.flush()
* assert(f.file.length === 18)
* }
*
* "be fun" in { f =>
* f.writer.write("fun!")
* f.writer.flush()
* assert(f.file.length === 17)
* }
* }
* }
*
*
*
* In this example, the tests actually required two fixture objects, a File and a FileWriter. In such situations you can
* simply define the FixtureParam type to be a tuple containing the objects, or as is done in this example, a case class containing
* the objects. For more information on the withFixture(OneArgTest) technique, see the documentation for fixture.WordSpec.
*
*
*
* Mixing in BeforeAndAfter
*
*
* In all the shared fixture examples shown so far, the activities of creating, setting up, and cleaning up the fixture objects have been
* performed during the test. This means that if an exception occurs during any of these activities, it will be reported as a test failure.
* Sometimes, however, you may want setup to happen before the test starts, and cleanup after the test has completed, so that if an
* exception occurs during setup or cleanup, the entire suite aborts and no more tests are attempted. The simplest way to accomplish this in ScalaTest is
* to mix in trait BeforeAndAfter. With this trait you can denote a bit of code to run before each test
* with before and/or after each test each test with after, like this:
*
*
*
* package org.scalatest.examples.wordspec.beforeandafter
*
* import org.scalatest._
* import collection.mutable.ListBuffer
*
* class ExampleSpec extends wordspec.AnyWordSpec with BeforeAndAfter {
*
* val builder = new StringBuilder
* val buffer = new ListBuffer[String]
*
* before {
* builder.append("ScalaTest is ")
* }
*
* after {
* builder.clear()
* buffer.clear()
* }
*
* "Testing" should {
* "be easy" in {
* builder.append("easy!")
* assert(builder.toString === "ScalaTest is easy!")
* assert(buffer.isEmpty)
* buffer += "sweet"
* }
*
* "be fun" in {
* builder.append("fun!")
* assert(builder.toString === "ScalaTest is fun!")
* assert(buffer.isEmpty)
* }
* }
* }
*
*
*
* Note that the only way before and after code can communicate with test code is via some side-effecting mechanism, commonly by
* reassigning instance vars or by changing the state of mutable objects held from instance vals (as in this example). If using
* instance vars or mutable objects held from instance vals you wouldn't be able to run tests in parallel in the same instance
* of the test class (on the JVM, not Scala.js) unless you synchronized access to the shared, mutable state. This is why ScalaTest's ParallelTestExecution trait extends
* OneInstancePerTest. By running each test in its own instance of the class, each test has its own copy of the instance variables, so you
* don't need to synchronize. If you mixed ParallelTestExecution into the ExampleSuite above, the tests would run in parallel just fine
* without any synchronization needed on the mutable StringBuilder and ListBuffer[String] objects.
*
*
*
* Although BeforeAndAfter provides a minimal-boilerplate way to execute code before and after tests, it isn't designed to enable stackable
* traits, because the order of execution would be non-obvious. If you want to factor out before and after code that is common to multiple test suites, you
* should use trait BeforeAndAfterEach instead, as shown later in the next section,
* composing fixtures by stacking traits.
*
*
* Composing fixtures by stacking traits
*
*
* In larger projects, teams often end up with several different fixtures that test classes need in different combinations,
* and possibly initialized (and cleaned up) in different orders. A good way to accomplish this in ScalaTest is to factor the individual
* fixtures into traits that can be composed using the stackable trait pattern. This can be done, for example, by placing
* withFixture methods in several traits, each of which call super.withFixture. Here's an example in
* which the StringBuilder and ListBuffer[String] fixtures used in the previous examples have been
* factored out into two stackable fixture traits named Builder and Buffer:
*
*
*
* package org.scalatest.examples.wordspec.composingwithfixture
*
* import org.scalatest._
* import collection.mutable.ListBuffer
*
* trait Builder extends TestSuiteMixin { this: TestSuite =>
*
* val builder = new StringBuilder
*
* abstract override def withFixture(test: NoArgTest) = {
* builder.append("ScalaTest is ")
* try super.withFixture(test) // To be stackable, must call super.withFixture
* finally builder.clear()
* }
* }
*
* trait Buffer extends TestSuiteMixin { this: TestSuite =>
*
* val buffer = new ListBuffer[String]
*
* abstract override def withFixture(test: NoArgTest) = {
* try super.withFixture(test) // To be stackable, must call super.withFixture
* finally buffer.clear()
* }
* }
*
* class ExampleSpec extends wordspec.AnyWordSpec with Builder with Buffer {
*
* "Testing" should {
* "be easy" in {
* builder.append("easy!")
* assert(builder.toString === "ScalaTest is easy!")
* assert(buffer.isEmpty)
* buffer += "sweet"
* }
*
* "be fun" in {
* builder.append("fun!")
* assert(builder.toString === "ScalaTest is fun!")
* assert(buffer.isEmpty)
* buffer += "clear"
* }
* }
* }
*
*
*
* By mixing in both the Builder and Buffer traits, ExampleSpec gets both fixtures, which will be
* initialized before each test and cleaned up after. The order the traits are mixed together determines the order of execution.
* In this case, Builder is “super” to Buffer. If you wanted Buffer to be “super”
* to Builder, you need only switch the order you mix them together, like this:
*
*
*
* class Example2Spec extends wordspec.AnyWordSpec with Buffer with Builder
*
*
*
* And if you only need one fixture you mix in only that trait:
*
*
*
* class Example3Spec extends wordspec.AnyWordSpec with Builder
*
*
*
* Another way to create stackable fixture traits is by extending the BeforeAndAfterEach
* and/or BeforeAndAfterAll traits.
* BeforeAndAfterEach has a beforeEach method that will be run before each test (like JUnit's setUp),
* and an afterEach method that will be run after (like JUnit's tearDown).
* Similarly, BeforeAndAfterAll has a beforeAll method that will be run before all tests,
* and an afterAll method that will be run after all tests. Here's what the previously shown example would look like if it
* were rewritten to use the BeforeAndAfterEach methods instead of withFixture:
*
*
*
* package org.scalatest.examples.wordspec.composingbeforeandaftereach
*
* import org.scalatest._
* import org.scalatest.BeforeAndAfterEach
* import collection.mutable.ListBuffer
*
* trait Builder extends BeforeAndAfterEach { this: Suite =>
*
* val builder = new StringBuilder
*
* override def beforeEach() {
* builder.append("ScalaTest is ")
* super.beforeEach() // To be stackable, must call super.beforeEach
* }
*
* override def afterEach() {
* try super.afterEach() // To be stackable, must call super.afterEach
* finally builder.clear()
* }
* }
*
* trait Buffer extends BeforeAndAfterEach { this: Suite =>
*
* val buffer = new ListBuffer[String]
*
* override def afterEach() {
* try super.afterEach() // To be stackable, must call super.afterEach
* finally buffer.clear()
* }
* }
*
* class ExampleSpec extends wordspec.AnyWordSpec with Builder with Buffer {
*
* "Testing" should {
* "be easy" in {
* builder.append("easy!")
* assert(builder.toString === "ScalaTest is easy!")
* assert(buffer.isEmpty)
* buffer += "sweet"
* }
*
* "be fun" in {
* builder.append("fun!")
* assert(builder.toString === "ScalaTest is fun!")
* assert(buffer.isEmpty)
* buffer += "clear"
* }
* }
* }
*
*
*
* To get the same ordering as withFixture, place your super.beforeEach call at the end of each
* beforeEach method, and the super.afterEach call at the beginning of each afterEach
* method, as shown in the previous example. It is a good idea to invoke super.afterEach in a try
* block and perform cleanup in a finally clause, as shown in the previous example, because this ensures the
* cleanup code is performed even if super.afterEach throws an exception.
*
*
*
* The difference between stacking traits that extend BeforeAndAfterEach versus traits that implement withFixture is
* that setup and cleanup code happens before and after the test in BeforeAndAfterEach, but at the beginning and
* end of the test in withFixture. Thus if a withFixture method completes abruptly with an exception, it is
* considered a failed test. By contrast, if any of the beforeEach or afterEach methods of BeforeAndAfterEach
* complete abruptly, it is considered an aborted suite, which will result in a SuiteAborted event.
*
*
* Shared tests
*
*
* Sometimes you may want to run the same test code on different fixture objects. In other words, you may want to write tests that are "shared"
* by different fixture objects. To accomplish this in a AnyWordSpec, you first place shared tests in behavior functions.
* These behavior functions will be invoked during the construction phase of any AnyWordSpec that uses them, so that the tests they
* contain will be registered as tests in that AnyWordSpec. For example, given this stack class:
*
*
*
* import scala.collection.mutable.ListBuffer
*
* class Stack[T] {
*
* val MAX = 10
* private val buf = new ListBuffer[T]
*
* def push(o: T) {
* if (!full)
* buf.prepend(o)
* 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 AnyWordSpec 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 AnyWordSpec that uses them. If they are shared
* between different AnyWordSpecs, however, you could also define them in a separate trait that is mixed into each AnyWordSpec
* 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.AnyWordSpec =>
*
* def nonEmptyStack(newStack: => Stack[Int], lastItemAdded: Int) {
*
* "be non-empty" in {
* assert(!newStack.empty)
* }
*
* "return the top item on peek" in {
* assert(newStack.peek === lastItemAdded)
* }
*
* "not remove the top item on peek" in {
* val stack = newStack
* val size = stack.size
* assert(stack.peek === lastItemAdded)
* assert(stack.size === size)
* }
*
* "remove the top item on pop" in {
* val stack = newStack
* val size = stack.size
* assert(stack.pop === lastItemAdded)
* assert(stack.size === size - 1)
* }
* }
*
* def nonFullStack(newStack: => Stack[Int]) {
*
* "not be full" in {
* assert(!newStack.full)
* }
*
* "add to the top on push" in {
* val stack = newStack
* 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 AnyWordSpec 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.AnyWordSpec 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 {
* assertThrows[IllegalStateException] {
* emptyStack.peek
* }
* }
*
* "complain on pop" in {
* assertThrows[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 {
* assertThrows[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> org.scalatest.run(new SharedTestExampleSpec)
* SharedTestExampleSpec:
* A Stack
* when empty
* - should be empty
* - should complain on peek
* - should complain on pop
* when it contains one item
* - should be non-empty
* - 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
* 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
* 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 AnyWordSpec is to make sure
* each invocation of a behavior function is in the context of a different surrounding when,
* should/must/can, or which clause, because a test's name is the concatenation of its
* surrounding clauses and after words, followed by the "spec text".
* For example, the following code in a AnyWordSpec would register a test with the name "A Stack when empty should be empty":
*
*
*
* "A Stack" when {
* "empty" should {
* "be empty" in {
* assert(emptyStack.empty)
* }
* }
* }
* // ...
*
*
*
* If the "be empty" test was factored out into a behavior function, it could be called repeatedly so long
* as each invocation of the behavior function is in the context of a different surrounding when clauses.
*
*
* @author Bill Venners
*/
@Finders(Array("org.scalatest.finders.WordSpecFinder"))
open class AnyWordSpec extends AnyWordSpecLike {
/**
* Returns a user friendly string for this suite, composed of the
* simple name of the class (possibly simplified further by removing dollar signs if added by the Scala interpeter) and, if this suite
* contains nested suites, the result of invoking toString on each
* of the nested suites, separated by commas and surrounded by parentheses.
*
* @return a user-friendly string for this suite
*/
override def toString: String = Suite.suiteToString(None, this)
}