Facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.
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 Ruby's RSpec tool, AnyFunSpec will feel familiar and comfortable; More generally, for any team that prefers BDD, AnyFunSpec 's nesting
and gentle guide to structuring text (with describe and it ) provide an excellent general-purpose choice for writing specification-style tests.
|
Here's an example AnyFunSpec
:
package org.scalatest.examples.funspec import org.scalatest.funspec.AnyFunSpec class SetSpec extends AnyFunSpec { describe("A Set") { describe("when empty") { it("should have size 0") { assert(Set.empty.size === 0) } it("should produce NoSuchElementException when head is invoked") { assertThrows[NoSuchElementException] { Set.empty.head } } } } }
A AnyFunSpec
contains describe clauses and tests. You define a describe clause
with describe
, and a test with either it
or they
.
describe
, it
, and they
are methods, defined in
AnyFunSpec
, which will be invoked
by the primary constructor of SetSpec
.
A describe clause names, or gives more information about, the subject (class or other entity) you are specifying
and testing. In the previous example, "A Set"
is the subject under specification and test. With each test you provide a string (the spec text) that specifies
one bit of behavior of the subject, and a block of code that tests that behavior.
You place the spec text between the parentheses, followed by the test code between curly
braces. The test code will be wrapped up as a function passed as a by-name parameter to
it
(or they
), which will register the test for later execution.
Note: the they
method is intended for use when the subject is plural, for example:
describe("The combinators") { they("should be easy to learn") {} they("should be efficient") {} they("should do something cool") {} }
A AnyFunSpec
'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 with the it
or they
methods while the AnyFunSpec
is
in its registration phase. Any attempt to register a test after the AnyFunSpec
has
entered its ready phase, i.e., after run
has been invoked on the AnyFunSpec
,
will be met with a thrown TestRegistrationClosedException
. The recommended style
of using AnyFunSpec
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
.
When you execute a AnyFunSpec
, it will send Formatter
s in the events it sends to the
Reporter
. ScalaTest's built-in reporters will report these events in such a way
that the output is easy to read as an informal specification of the subject being tested.
For example, were you to run SetSpec
from within the Scala interpreter:
scala> org.scalatest.run(new SetSpec)
You would see:
A Set when empty - should have size 0 - should produce NoSuchElementException when head is invoked
Or, to run just the “A Set when empty should have size 0
” test, you could pass that test's name, or any unique substring of the
name, such as "size 0"
or even just "0"
. Here's an example:
scala> org.scalatest.run(new SetSuite, "size 0") A Set when empty - should have size 0
You can also pass to execute
a config map of key-value
pairs, which will be passed down into suites and tests, as well as other parameters that configure the run itself.
For more information on running in the Scala interpreter, see the documentation for execute
(below) and the
ScalaTest shell.
The execute
method invokes a run
method that takes two
parameters. This run
method, which actually executes the suite, will usually be invoked by a test runner, such
as run
, tools.Runner
, a build tool, or an IDE.
Note: AnyFunSpec
's syntax is in great part inspired by RSpec, a Ruby BDD framework.
To support the common use case of temporarily disabling a test, with the
good intention of resurrecting the test at a later time, AnyFunSpec
provides registration
methods that start with ignore
instead of it
or they
. For example, to temporarily
disable the test with the text "should have size 0"
, just change “it
” into “ignore
,” like this:
package org.scalatest.examples.funspec.ignore import org.scalatest.funspec.AnyFunSpec class SetSpec extends AnyFunSpec { describe("A Set") { describe("when empty") { ignore("should have size 0") { assert(Set.empty.size === 0) } it("should produce NoSuchElementException when head is invoked") { assertThrows[NoSuchElementException] { Set.empty.head } } } } }
If you run this version of SetSpec
with:
scala> org.scalatest.run(new SetSpec)
It will run only the second test and report that the first test was ignored:
A Set when empty - should have size 0 !!! IGNORED !!! - should produce NoSuchElementException when head is invoked
If you wish to temporarily ignore an entire suite of tests, you can (on the JVM, not Scala.js) annotate the test class with @Ignore
, like this:
package org.scalatest.examples.funspec.ignoreall import org.scalatest.funsuite.AnyFunSpec import org.scalatest.Ignore @Ignore class SetSpec extends AnyFunSpec { describe("A Set") { describe("when empty") { it("should have size 0") { assert(Set.empty.size === 0) } it("should produce NoSuchElementException when head is invoked") { assertThrows[NoSuchElementException] { Set.empty.head } } } } }
When you mark a test class with a tag annotation, ScalaTest will mark each test defined in that class with that tag.
Thus, marking the SetSpec
in the above example with the @Ignore
tag annotation means that both tests
in the class will be ignored. If you run the 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.
One of the parameters to AnyFunSpec
'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 AnyFunSpec
'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 one of its apply
methods.
The Informer
will then pass the information to the Reporter
via an InfoProvided
event.
Here's an example in which the Informer
returned by info
is used implicitly by the
Given
, When
, and Then
methods of trait GivenWhenThen
:
package org.scalatest.examples.funspec.info import collection.mutable import org.scalatest._ class SetSpec extends funspec.AnyFunSpec with GivenWhenThen { describe("A mutable Set") { it("should allow an element to be added") { Given("an empty mutable Set") val set = mutable.Set.empty[String] When("an element is added") set += "clarity" Then("the Set should have size 1") assert(set.size === 1) And("the Set should contain the added element") assert(set.contains("clarity")) info("That's all folks!") } } }
If you run this AnyFunSpec
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!
AnyFunSpec
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 AnyFunSpec
that uses markup
:
package org.scalatest.examples.funspec.markup import collection.mutable import org.scalatest._ class SetSpec extends funspec.AnyFunSpec 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. """ } describe("A mutable Set") { it("should allow an element to be added") { Given("an empty mutable Set") val set = mutable.Set.empty[String] When("an element is added") set += "clarity" Then("the Set should have size 1") assert(set.size === 1) And("the Set should contain the added element") assert(set.contains("clarity")) markup("This test finished with a **bold** statement!") } } }
Although all of ScalaTest's built-in reporters will display the markup text in some form,
the HTML reporter will format the markup information into HTML. Thus, the main purpose of markup
is to
add nicely formatted text to HTML reports. Here's what the above SetSpec
would look like in the HTML reporter:
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.funspec.note import collection.mutable import org.scalatest._ class SetSpec extends funspec.AnyFunSpec { describe("A mutable Set") { it("should allow an element to be added") { info("info is recorded") markup("markup is *also* recorded") note("notes are sent immediately") alert("alerts are also sent immediately") val set = mutable.Set.empty[String] set += "clarity" assert(set.size === 1) assert(set.contains("clarity")) } } }
Because note
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.)
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, has not yet been implemented.
You can mark a test as pending in AnyFunSpec
by placing "(pending)
" after the
test name, like this:
package org.scalatest.examples.funspec.pending import org.scalatest._ class SetSpec extends funspec.AnyFunSpec { describe("A Set") { describe("when empty") { it("should have size 0") (pending) it("should produce NoSuchElementException when head is invoked") { assertThrows[NoSuchElementException] { Set.empty.head } } } } }
(Note: "(pending)
" is the body of the test. Thus the test contains just one statement, an invocation
of the pending
method, which throws TestPendingException
.)
If you run this version of SetSpec
with:
scala> org.scalatest.run(new SetSpec)
It will run both tests, but report that the test named "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
A AnyFunSpec
's tests may be classified into groups by tagging them with string names.
As with any suite, when executing a AnyFunSpec
, groups of tests can
optionally be included and/or excluded. To tag a AnyFunSpec
'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 AnyFunSpec
s like this:
package org.scalatest.examples.funspec.tagging import org.scalatest.Tag object DbTest extends Tag("com.mycompany.tags.DbTest")
Given these definitions, you could place AnyFunSpec
tests into groups with tags like this:
import org.scalatest.funspec.AnyFunSpec import org.scalatest.tagobjects.Slow class SetSpec extends AnyFunSpec { describe("A Set") { describe("when empty") { it("should have size 0", Slow) { assert(Set.empty.size === 0) } it("should produce NoSuchElementException when head is invoked", Slow, DbTest) { 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 AnyFunSpec
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.
A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code.
ScalaTest recommends three techniques to eliminate such code duplication:
withFixture
Each technique is geared towards helping you reduce code duplication without introducing
instance var
s, shared mutable objects, or other dependencies between tests. Eliminating shared
mutable state across tests will make your test code easier to reason about and more amenable for parallel
test execution.
The following sections describe these techniques, including explaining the recommended usage for each. But first, here's a table summarizing the options:
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:
|
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. |
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.funspec.getfixture import org.scalatest.funspec.AnyFunSpec import collection.mutable.ListBuffer class ExampleSpec extends AnyFunSpec { class Fixture { val builder = new StringBuilder("ScalaTest is ") val buffer = new ListBuffer[String] } def fixture = new Fixture describe("Testing") { it("should be easy") { val f = fixture f.builder.append("easy!") assert(f.builder.toString === "ScalaTest is easy!") assert(f.buffer.isEmpty) f.buffer += "sweet" } it("should be fun") { val f = fixture f.builder.append("fun!") assert(f.builder.toString === "ScalaTest is fun!") assert(f.buffer.isEmpty) } } }
The “f.
” in front of each use of a fixture object provides a visual indication of which objects
are part of the fixture, but if you prefer, you can import the the members with “import f._
” and use the names directly.
If you need to configure fixture objects differently in different tests, you can pass configuration into the get-fixture method. For example, if you could pass in an initial value for a mutable fixture object as a parameter to the get-fixture method.
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.funspec.fixturecontext import collection.mutable.ListBuffer import org.scalatest.funspec.AnyFunSpec class ExampleSpec extends AnyFunSpec { trait Builder { val builder = new StringBuilder("ScalaTest is ") } trait Buffer { val buffer = ListBuffer("ScalaTest", "is") } describe("Testing") { // This test needs the StringBuilder fixture it("should be productive") { new Builder { builder.append("productive!") assert(builder.toString === "ScalaTest is productive!") } } } describe("Test code") { // This test needs the ListBuffer[String] fixture it("should be readable") { new Buffer { buffer += ("readable!") assert(buffer === List("ScalaTest", "is", "readable!")) } } // This test needs both the StringBuilder and ListBuffer it("should be clear and concise") { new Builder with Buffer { builder.append("clear!") buffer += ("concise!") assert(builder.toString === "ScalaTest is clear!") assert(buffer === List("ScalaTest", "is", "concise!")) } } } }
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 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. In other words, instead of writing
“test()
”, you should write “super.withFixture(test)
”, like this:
// Your implementation override def withFixture(test: NoArgTest) = { // Perform setup try super.withFixture(test) // Invoke the test function finally { // Perform cleanup } }
Here's an example in which withFixture(NoArgTest)
is used to take a snapshot of the working directory if a test fails, and
send that information to the reporter:
package org.scalatest.examples.funspec.noargtest import java.io.File import org.scalatest._ class ExampleSpec extends funspec.AnyFunSpec { override def withFixture(test: NoArgTest) = { try super.withFixture(test) match { case failed: Failed => val currDir = new File(".") val fileNames = currDir.list() info("Dir snapshot: " + fileNames.mkString(", ")) failed case other => other } } describe("This test") { it("should succeed") { assert(1 + 1 === 2) } it("should fail") { 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.
If you need to both pass a fixture object into a test and perform cleanup at the end of the test, you'll need to use the loan pattern. If different tests need different fixtures that require cleanup, you can implement the loan pattern directly by writing loan-fixture methods. A loan-fixture method takes a function whose body forms part or all of a test's code. It creates a fixture, passes it to the test code by invoking the function, then cleans up the fixture after the function returns.
The following example shows three tests that use two fixtures, a database and a file. Both require cleanup after, so each is provided via a
loan-fixture method. (In this example, the database is simulated with a StringBuffer
.)
package org.scalatest.examples.funspec.loanfixture import java.util.concurrent.ConcurrentHashMap object DbServer { // Simulating a database server type Db = StringBuffer private val databases = new ConcurrentHashMap[String, Db] def createDb(name: String): Db = { val db = new StringBuffer databases.put(name, db) db } def removeDb(name: String) { databases.remove(name) } } import org.scalatest.funspec.AnyFunSpec import DbServer._ import java.util.UUID.randomUUID import java.io._ class ExampleSpec extends AnyFunSpec { 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 } describe("Testing") { // This test needs the file fixture it("should be productive") { withFile { (file, writer) => writer.write("productive!") writer.flush() assert(file.length === 24) } } } describe("Test code") { // This test needs the database fixture it("should be readable") { withDatabase { db => db.append("readable!") assert(db.toString === "ScalaTest is readable!") } } // This test needs both the file and the database it("should be clear and concise") { withDatabase { db => withFile { (file, writer) => // loan-fixture methods compose db.append("clear!") writer.write("concise!") writer.flush() assert(db.toString === "ScalaTest is clear!") assert(file.length === 21) } } } } }
As demonstrated by the last test, loan-fixture methods compose. Not only do loan-fixture methods allow you to give each test the fixture it needs, they allow you to give a test multiple fixtures and clean everything up afterwards.
Also demonstrated in this example is the technique of giving each test its own "fixture sandbox" to play in. When your fixtures involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is done in this example. This keeps tests completely isolated, allowing you to run them in parallel if desired.
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 FixtureSuite
and overriding withFixture(OneArgTest)
.
Each test in a FixtureSuite
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
. In other words, instead of
writing “test(theFixture)
”, you'd delegate responsibility for
invoking the test function to the withFixture(NoArgTest)
method of the same instance by writing:
withFixture(test.toNoArgTest(theFixture))
Here's a complete example:
package org.scalatest.examples.funspec.oneargtest import org.scalatest.funspec import java.io._ class ExampleSpec extends funspec.FixtureAnyFunSpec { case class FixtureParam(file: File, writer: FileWriter) def withFixture(test: OneArgTest) = { // create the fixture val file = File.createTempFile("hello", "world") val writer = new FileWriter(file) val theFixture = FixtureParam(file, writer) try { writer.write("ScalaTest is ") // set up the fixture withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test } finally writer.close() // clean up the fixture } describe("Testing") { it("should be easy") { f => f.writer.write("easy!") f.writer.flush() assert(f.file.length === 18) } it("should be fun") { 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 FixtureAnyFunSpec
.
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.funspec.beforeandafter import org.scalatest.funspec.AnyFunSpec import org.scalatest.BeforeAndAfter import collection.mutable.ListBuffer class ExampleSpec extends AnyFunSpec with BeforeAndAfter { val builder = new StringBuilder val buffer = new ListBuffer[String] before { builder.append("ScalaTest is ") } after { builder.clear() buffer.clear() } describe("Testing") { it("should be easy") { builder.append("easy!") assert(builder.toString === "ScalaTest is easy!") assert(buffer.isEmpty) buffer += "sweet" } it("should be fun") { 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 var
s or by changing the state of mutable objects held from instance val
s (as in this example). If using
instance var
s or mutable objects held from instance val
s you wouldn't be able to run tests in parallel in the same instance
of the test class (on the JVM, not Scala.js) unless you synchronized access to the shared, mutable state. This is why ScalaTest'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.
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.funspec.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 funspec.AnyFunSpec with Builder with Buffer { describe("Testing") { it("should be easy") { builder.append("easy!") assert(builder.toString === "ScalaTest is easy!") assert(buffer.isEmpty) buffer += "sweet" } it("should be fun") { builder.append("fun!") assert(builder.toString === "ScalaTest is fun!") assert(buffer.isEmpty) buffer += "clear" } } }
By mixing in both the Builder
and Buffer
traits, ExampleSuite
gets both fixtures, which will be
initialized before each test and cleaned up after. The order the traits are mixed together determines the order of execution.
In this case, Builder
is “super” 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 AnyFunSpec with Buffer with Builder
And if you only need one fixture you mix in only that trait:
class Example3Spec extends AnyFunSpec 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.funspec.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 funspec.AnyFunSpec with Builder with Buffer { describe("Testing") { it("should be easy") { builder.append("easy!") assert(builder.toString === "ScalaTest is easy!") assert(buffer.isEmpty) buffer += "sweet" } it("should be fun") { builder.append("fun!") assert(builder.toString === "ScalaTest is fun!") assert(buffer.isEmpty) buffer += "clear" } } }
To get the same ordering as withFixture
, place 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.
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 AnyFunSpec
, you first place shared tests in behavior functions. These behavior functions will be
invoked during the construction phase of any AnyFunSpec
that uses them, so that the tests they contain will be registered as tests in that AnyFunSpec
.
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 AnyFunSpec
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 AnyFunSpec
that uses them. If they are shared
between different AnyFunSpec
s, however, you could also define them in a separate trait that is mixed into each AnyFunSpec
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: AnyFunSpec => def nonEmptyStack(newStack: => Stack[Int], lastItemAdded: Int) { it("should be non-empty") { assert(!newStack.empty) } it("should return the top item on peek") { assert(newStack.peek === lastItemAdded) } it("should not remove the top item on peek") { val stack = newStack val size = stack.size assert(stack.peek === lastItemAdded) assert(stack.size === size) } it("should remove the top item on pop") { val stack = newStack val size = stack.size assert(stack.pop === lastItemAdded) assert(stack.size === size - 1) } } def nonFullStack(newStack: => Stack[Int]) { it("should not be full") { assert(!newStack.full) } it("should add to the top on push") { 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 AnyFunSpec
offers a DSL for the purpose,
which looks like this:
it should behave like nonEmptyStack(stackWithOneItem, lastValuePushed) it should 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:
it should behave like nonEmptyStack // assuming lastValuePushed is also in scope inside nonEmptyStack it should behave like nonFullStack
The recommended style, however, is the functional, pass-all-the-needed-values-in style. Here's an example:
class SharedTestExampleSpec extends AnyFunSpec 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 describe("A Stack") { describe("(when empty)") { it("should be empty") { assert(emptyStack.empty) } it("should complain on peek") { assertThrows[IllegalStateException] { emptyStack.peek } } it("should complain on pop") { assertThrows[IllegalStateException] { emptyStack.pop } } } describe("(with one item)") { it should behave like nonEmptyStack(stackWithOneItem, lastValuePushed) it should behave like nonFullStack(stackWithOneItem) } describe("(with one item less than capacity)") { it should behave like nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed) it should behave like nonFullStack(stackWithOneItemLessThanCapacity) } describe("(full)") { it("should be full") { assert(fullStack.full) } it should behave like nonEmptyStack(fullStack, lastValuePushed) it("should complain on a push") { 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 StackSpec)
A Stack (when empty)
- should be empty
- should complain on peek
- should complain on pop
A Stack (with 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 (with 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 (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 AnyFunSpec
is to surround
each invocation of a behavior function with a describe
clause, which will prepend a string to each test name.
For example, the following code in a AnyFunSpec
would register a test with the name "A Stack (when empty) should be empty"
:
describe("A Stack") { describe("(when empty)") { it("should be empty") { 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 inside a different set of describe
clauses.
Implementation trait for class AnyFunSpec
, which
facilitates a “behavior-driven” style of development (BDD),
in which tests are combined with text that specifies the behavior the tests
verify.
Implementation trait for class AnyFunSpec
, which
facilitates a “behavior-driven” style of development (BDD),
in which tests are combined with text that specifies the behavior the tests
verify.
AnyFunSpec
is a class, not a trait,
to minimize compile time given there is a slight compiler overhead to
mixing in traits compared to extending classes. If you need to mix the
behavior of AnyFunSpec
into some other class, you can use this
trait instead, because class AnyFunSpec
does nothing more than
extend this trait and add a nice toString
implementation.
See the documentation of the class for a detailed
overview of AnyFunSpec
.
A sister class to org.scalatest.funspec.AnyFunSpec
that can pass a fixture object into its tests.
A sister class to org.scalatest.funspec.AnyFunSpec
that can pass a fixture object into its tests.
Recommended Usage:
Use class FixtureAnyFunSpec in situations for which AnyFunSpec
would be a good choice, when all or most tests need the same fixture objects
that must be cleaned up afterwards. Note: FixtureAnyFunSpec is intended for use in special situations, with class AnyFunSpec used for general needs. For
more insight into where FixtureAnyFunSpec fits in the big picture, see the withFixture(OneArgTest) subsection of the Shared fixtures section in the documentation for class AnyFunSpec .
|
Class FixtureAnyFunSpec
behaves similarly to class org.scalatest.funspec.AnyFunSpec
, except that tests may have a
fixture parameter. The type of the
fixture parameter is defined by the abstract FixtureParam
type, which is a member of this class.
This class also contains an abstract withFixture
method. This withFixture
method
takes a OneArgTest
, which is a nested trait defined as a member of this class.
OneArgTest
has an apply
method that takes a FixtureParam
.
This apply
method is responsible for running a test.
This class's runTest
method delegates the actual running of each test to withFixture(OneArgTest)
, passing
in the test code to run via the OneArgTest
argument. The withFixture(OneArgTest)
method (abstract in this class) is responsible
for creating the fixture argument and passing it to the test function.
Subclasses of this class must, therefore, do three things differently from a plain old org.scalatest.funspec.AnyFunSpec
:
FixtureParam
withFixture(OneArgTest)
methodIf the fixture you want to pass into your tests consists of multiple objects, you will need to combine them into one object to use this class. One good approach to passing multiple fixture objects is to encapsulate them in a case class. Here's an example:
case class FixtureParam(file: File, writer: FileWriter)
To enable the stacking of traits that define withFixture(NoArgTest)
, it is a good idea to let
withFixture(NoArgTest)
invoke the test function instead of invoking the test
function directly. To do so, you'll need to convert the OneArgTest
to a NoArgTest
. You can do that by passing
the fixture object to the toNoArgTest
method of OneArgTest
. In other words, instead of
writing “test(theFixture)
”, you'd delegate responsibility for
invoking the test function to the withFixture(NoArgTest)
method of the same instance by writing:
withFixture(test.toNoArgTest(theFixture))
Here's a complete example:
package org.scalatest.examples.funspec.oneargtest import org.scalatest.funspec import java.io._ class ExampleSpec extends FixtureAnyFunSpec { case class FixtureParam(file: File, writer: FileWriter) def withFixture(test: OneArgTest) = { // create the fixture val file = File.createTempFile("hello", "world") val writer = new FileWriter(file) val theFixture = FixtureParam(file, writer) try { writer.write("ScalaTest is ") // set up the fixture withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test } finally writer.close() // clean up the fixture } describe("Testing") { it("should be easy") { f => f.writer.write("easy!") f.writer.flush() assert(f.file.length === 18) } it("should be fun") { f => f.writer.write("fun!") f.writer.flush() assert(f.file.length === 17) } } }
If a test fails, the OneArgTest
function will result in a Failed wrapping the exception describing the failure.
To ensure clean up happens even if a test fails, you should invoke the test function from inside a try
block and do the cleanup in a
finally
clause, as shown in the previous example.
If multiple test classes need the same fixture, you can define the FixtureParam
and withFixture(OneArgTest)
implementations
in a trait, then mix that trait into the test classes that need it. For example, if your application requires a database and your integration tests
use that database, you will likely have many test classes that need a database fixture. You can create a "database fixture" trait that creates a
database with a unique name, passes the connector into the test, then removes the database once the test completes. This is shown in the following example:
package org.scalatest.examples.fixture.funspec.sharing import java.util.concurrent.ConcurrentHashMap import org.scalatest.funspec import DbServer._ import java.util.UUID.randomUUID object DbServer { // Simulating a database server type Db = StringBuffer private val databases = new ConcurrentHashMap[String, Db] def createDb(name: String): Db = { val db = new StringBuffer databases.put(name, db) db } def removeDb(name: String) { databases.remove(name) } } trait DbFixture { this: FixtureSuite => type FixtureParam = Db // Allow clients to populate the database after // it is created def populateDb(db: Db) {} def withFixture(test: OneArgTest) = { val dbName = randomUUID.toString val db = createDb(dbName) // create the fixture try { populateDb(db) // setup the fixture withFixture(test.toNoArgTest(db)) // "loan" the fixture to the test } finally removeDb(dbName) // clean up the fixture } } class ExampleSpec extends FixtureAnyFunSpec with DbFixture { override def populateDb(db: Db) { // setup the fixture db.append("ScalaTest is ") } describe("Testing") { it("should be easy") { db => db.append("easy!") assert(db.toString === "ScalaTest is easy!") } it("should be fun") { db => db.append("fun!") assert(db.toString === "ScalaTest is fun!") } } // This test doesn't need a Db describe("Test code") { it("should be clear") { () => val buf = new StringBuffer buf.append("ScalaTest code is ") buf.append("clear!") assert(buf.toString === "ScalaTest code is clear!") } } }
Often when you create fixtures in a trait like DbFixture
, you'll still need to enable individual test classes
to "setup" a newly created fixture before it gets passed into the tests. A good way to accomplish this is to pass the newly
created fixture into a setup method, like populateDb
in the previous example, before passing it to the test
function. Classes that need to perform such setup can override the method, as does ExampleSpec
.
If a test doesn't need the fixture, you can indicate that by providing a no-arg instead of a one-arg function, as is done in the
third test in the previous example, “Test code should be clear
”. In other words, instead of starting your function literal
with something like “db =>
”, you'd start it with “() =>
”. For such tests, runTest
will not invoke withFixture(OneArgTest)
. It will instead directly invoke withFixture(NoArgTest)
.
Both examples shown above demonstrate the technique of giving each test its own "fixture sandbox" to play in. When your fixtures
involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is
done in these examples. This keeps tests completely isolated, allowing you to run them in parallel if desired. You could mix
ParallelTestExecution
into either of these ExampleSpec
classes, and the tests would run in parallel just fine.
Implementation trait for class FixtureAnyFunSpec
, which is
a sister class to org.scalatest.funspec.AnyFunSpec
that can pass a
fixture object into its tests.
Implementation trait for class FixtureAnyFunSpec
, which is
a sister class to org.scalatest.funspec.AnyFunSpec
that can pass a
fixture object into its tests.
FixtureAnyFunSpec
is a class,
not a trait, to minimize compile time given there is a slight compiler
overhead to mixing in traits compared to extending classes. If you need
to mix the behavior of FixtureAnyFunSpec
into some other
class, you can use this trait instead, because class
FixtureAnyFunSpec
does nothing more than extend this trait and add a nice toString
implementation.
See the documentation of the class for a detailed
overview of FixtureAnyFunSpec
.
A sister class to org.scalatest.funspec.AnyFunSpec
that isolates tests by running each test in its own
instance of the test class, and for each test, only executing the path leading to that test.
A sister class to org.scalatest.funspec.AnyFunSpec
that isolates tests by running each test in its own
instance of the test class, and for each test, only executing the path leading to that test.
Class PathAnyFunSpec
behaves similarly to class org.scalatest.funspec.AnyFunSpec
, except that tests
are isolated based on their path. The purpose of PathAnyFunSpec
is to facilitate writing
specification-style tests for mutable objects in a clear, boilerpate-free way. To test mutable objects, you need to
mutate them. Using a path class, you can make a statement in text, then implement that statement in code (including
mutating state), and nest and combine these test/code pairs in any way you wish. Each test will only see
the side effects of code that is in blocks that enclose the test. Here's an example:
import org.scalatest.funspec import org.scalatest.matchers.should.Matchers import scala.collection.mutable.ListBuffer class ExampleSpec extends funspec.PathAnyFunSpec with Matchers { describe("A ListBuffer") { val buf = ListBuffer.empty[Int] // This implements "A ListBuffer" it("should be empty when created") { // This test sees: // val buf = ListBuffer.empty[Int] // So buf is: ListBuffer() buf should be ('empty) } describe("when 1 is appended") { buf += 1 // This implements "when 1 is appended", etc... it("should contain 1") { // This test sees: // val buf = ListBuffer.empty[Int] // buf += 1 // So buf is: ListBuffer(1) buf.remove(0) should equal (1) buf should be ('empty) } describe("when 2 is appended") { buf += 2 it("should contain 1 and 2") { // This test sees: // val buf = ListBuffer.empty[Int] // buf += 1 // buf += 2 // So buf is: ListBuffer(1, 2) buf.remove(0) should equal (1) buf.remove(0) should equal (2) buf should be ('empty) } describe("when 2 is removed") { buf -= 2 it("should contain only 1 again") { // This test sees: // val buf = ListBuffer.empty[Int] // buf += 1 // buf += 2 // buf -= 2 // So buf is: ListBuffer(1) buf.remove(0) should equal (1) buf should be ('empty) } } describe("when 3 is appended") { buf += 3 it("should contain 1, 2, and 3") { // This test sees: // val buf = ListBuffer.empty[Int] // buf += 1 // buf += 2 // buf += 3 // So buf is: ListBuffer(1, 2, 3) buf.remove(0) should equal (1) buf.remove(0) should equal (2) buf.remove(0) should equal (3) buf should be ('empty) } } } describe("when 88 is appended") { buf += 88 it("should contain 1 and 88") { // This test sees: // val buf = ListBuffer.empty[Int] // buf += 1 // buf += 88 // So buf is: ListBuffer(1, 88) buf.remove(0) should equal (1) buf.remove(0) should equal (88) buf should be ('empty) } } } it("should have size 0 when created") { // This test sees: // val buf = ListBuffer.empty[Int] // So buf is: ListBuffer() buf should have size 0 } } }
Note that the above class is organized by writing a bit of specification text that opens a new block followed
by, at the top of the new block, some code that "implements" or "performs" what is described in the text. This is repeated as
the mutable object (here, a ListBuffer
), is prepared for the enclosed tests. For example:
describe("A ListBuffer") { val buf = ListBuffer.empty[Int]
Or:
describe("when 2 is appended") { buf += 2
Note also that although each test mutates the ListBuffer
, none of the other tests observe those
side effects:
it("should contain 1") { buf.remove(0) should equal (1) // ... } describe("when 2 is appended") { buf += 2 it("should contain 1 and 2") { // This test does not see the buf.remove(0) from the previous test, // so the first element in the ListBuffer is again 1 buf.remove(0) should equal (1) buf.remove(0) should equal (2)
This kind of isolation of tests from each other is a consequence of running each test in its own instance of the test
class, and can also be achieved by simply mixing OneInstancePerTest
into a regular
org.scalatest.funspec.AnyFunSpec
. However, PathAnyFunSpec
takes isolation one step further: a test
in a PathAnyFunSpec
does not observe side effects performed outside tests in earlier blocks that do not
enclose it. Here's an example:
describe("when 2 is removed") { buf -= 2 // ... } describe("when 3 is appended") { buf += 3 it("should contain 1, 2, and 3") { // This test does not see the buf -= 2 from the earlier "when 2 is removed" block, // because that block does not enclose this test, so the second element in the // ListBuffer is still 2 buf.remove(0) should equal (1) buf.remove(0) should equal (2) buf.remove(0) should equal (3)
Running the full ExampleSpec
, shown above, in the Scala interpeter would give you:
scala> import org.scalatest._
import org.scalatest._
scala> run(new ExampleSpec)
ExampleSpec:
A ListBuffer
- should be empty when created
when 1 is appended
- should contain 1
when 2 is appended
- should contain 1 and 2
when 2 is removed
- should contain only 1 again
when 3 is appended
- should contain 1, 2, and 3
when 88 is appended
- should contain 1 and 88
- should have size 0 when created
Note: class PathAnyFunSpec
's approach to isolation was inspired in part by the
specsy framework, written by Esko Luontola.
A test fixture is objects or other artifacts (such as files, sockets, database
connections, etc.) used by tests to do their work.
If a fixture is used by only one test, then the definitions of the fixture objects can
be local to the method. If multiple tests need to share an immutable fixture, you can simply
assign them to instance variables. If multiple tests need to share mutable fixture objects or var
s,
there's one and only one way to do it in a PathAnyFunSpec
: place the mutable objects lexically before
the test. Any mutations needed by the test must be placed lexically before and/or after the test.
As used here, "Lexically before" means that the code needs to be executed during construction of that test's
instance of the test class to reach the test (or put another way, the
code is along the "path to the test.") "Lexically after" means that the code needs to be executed to exit the
constructor after the test has been executed.
The reason lexical placement is the one and only one way to share fixtures in a PathAnyFunSpec
is because
all of its lifecycle methods are overridden and declared final
. Thus you can't mix in BeforeAndAfter
or
BeforeAndAfterEach
, because both override runTest
, which is final
in
a PathAnyFunSpec
. You also can't override withFixture
, because PathAnyFunSpec
extends Suite
not TestSuite
,
where withFixture
is defined. In short:
In a PathAnyFunSpec , if you need some code to execute before a test, place that code lexically before
the test. If you need some code to execute after a test, place that code lexically after the test.
|
---|
The reason the life cycle methods are final, by the way, is to prevent users from attempting to combine
a PathAnyFunSpec
's approach to isolation with other ways ScalaTest provides to share fixtures or
execute tests, because doing so could make the resulting test code hard to reason about. A
PathAnyFunSpec
's execution model is a bit magical, but because it executes in one and only one
way, users should be able to reason about the code.
To help you visualize how a PathAnyFunSpec
is executed, consider the following variant of
ExampleSpec
that includes print statements:
import org.scalatest.funspec import org.scalatest.matchers.Matchers import scala.collection.mutable.ListBuffer class ExampleSpec extends funspec.PathAnyFunSpec with Matchers { println("Start of: ExampleSpec") describe("A ListBuffer") { println("Start of: A ListBuffer") val buf = ListBuffer.empty[Int] it("should be empty when created") { println("In test: should be empty when created; buf is: " + buf) buf should be ('empty) } describe("when 1 is appended") { println("Start of: when 1 is appended") buf += 1 it("should contain 1") { println("In test: should contain 1; buf is: " + buf) buf.remove(0) should equal (1) buf should be ('empty) } describe("when 2 is appended") { println("Start of: when 2 is appended") buf += 2 it("should contain 1 and 2") { println("In test: should contain 1 and 2; buf is: " + buf) buf.remove(0) should equal (1) buf.remove(0) should equal (2) buf should be ('empty) } describe("when 2 is removed") { println("Start of: when 2 is removed") buf -= 2 it("should contain only 1 again") { println("In test: should contain only 1 again; buf is: " + buf) buf.remove(0) should equal (1) buf should be ('empty) } println("End of: when 2 is removed") } describe("when 3 is appended") { println("Start of: when 3 is appended") buf += 3 it("should contain 1, 2, and 3") { println("In test: should contain 1, 2, and 3; buf is: " + buf) buf.remove(0) should equal (1) buf.remove(0) should equal (2) buf.remove(0) should equal (3) buf should be ('empty) } println("End of: when 3 is appended") } println("End of: when 2 is appended") } describe("when 88 is appended") { println("Start of: when 88 is appended") buf += 88 it("should contain 1 and 88") { println("In test: should contain 1 and 88; buf is: " + buf) buf.remove(0) should equal (1) buf.remove(0) should equal (88) buf should be ('empty) } println("End of: when 88 is appended") } println("End of: when 1 is appended") } it("should have size 0 when created") { println("In test: should have size 0 when created; buf is: " + buf) buf should have size 0 } println("End of: A ListBuffer") } println("End of: ExampleSpec") println() }
Running the above version of ExampleSpec
in the Scala interpreter will give you output similar to:
scala> import org.scalatest._ import org.scalatest._ scala> run(new ExampleSpec) ExampleSpec: Start of: ExampleSpec Start of: A ListBuffer In test: should be empty when created; buf is: ListBuffer() End of: A ListBuffer End of: ExampleSpec Start of: ExampleSpec Start of: A ListBuffer Start of: when 1 is appended In test: should contain 1; buf is: ListBuffer(1) ExampleSpec: End of: when 1 is appended End of: A ListBuffer End of: ExampleSpec Start of: ExampleSpec Start of: A ListBuffer Start of: when 1 is appended Start of: when 2 is appended In test: should contain 1 and 2; buf is: ListBuffer(1, 2) End of: when 2 is appended End of: when 1 is appended End of: A ListBuffer End of: ExampleSpec Start of: ExampleSpec Start of: A ListBuffer Start of: when 1 is appended Start of: when 2 is appended Start of: when 2 is removed In test: should contain only 1 again; buf is: ListBuffer(1) End of: when 2 is removed End of: when 2 is appended End of: when 1 is appended End of: A ListBuffer End of: ExampleSpec Start of: ExampleSpec Start of: A ListBuffer Start of: when 1 is appended Start of: when 2 is appended Start of: when 3 is appended In test: should contain 1, 2, and 3; buf is: ListBuffer(1, 2, 3) End of: when 3 is appended End of: when 2 is appended End of: when 1 is appended End of: A ListBuffer End of: ExampleSpec Start of: ExampleSpec Start of: A ListBuffer Start of: when 1 is appended Start of: when 88 is appended In test: should contain 1 and 88; buf is: ListBuffer(1, 88) End of: when 88 is appended End of: when 1 is appended End of: A ListBuffer End of: ExampleSpec Start of: ExampleSpec Start of: A ListBuffer In test: should have size 0 when created; buf is: ListBuffer() End of: A ListBuffer End of: ExampleSpec A ListBuffer - should be empty when created when 1 is appended - should contain 1 when 2 is appended - should contain 1 and 2 when 2 is removed - should contain only 1 again when 3 is appended - should contain 1, 2, and 3 when 88 is appended - should contain 1 and 88 - should have size 0 when created
Note that each test is executed in order of appearance in the PathAnyFunSpec
, and that only
those println
statements residing in blocks that enclose the test being run are executed. Any
println
statements in blocks that do not form the "path" to a test are not executed in the
instance of the class that executes that test.
To provide its special brand of test isolation, PathAnyFunSpec
executes quite differently from its
sister class in org.scalatest.funspec
. An org.scalatest.funspec.AnyFunSpec
registers tests during construction and executes them when run
is invoked. An
org.scalatest.funspec.PathAnyFunSpec
, by contrast, runs each test in its own instance while that
instance is being constructed. During construction, it registers not the tests to run, but the results of
running those tests. When run
is invoked on a PathAnyFunSpec
, it reports the registered
results and does not run the tests again. If run
is invoked a second or third time, in fact,
a PathAnyFunSpec
will each time report the same results registered during construction. If you want
to run the tests of a PathAnyFunSpec
anew, you'll need to create a new instance and invoke
run
on that.
A PathAnyFunSpec
will create one instance for each "leaf" node it contains. The main kind of leaf node is
a test, such as:
// One instance will be created for each test it("should be empty when created") { buf should be ('empty) }
However, an empty scope (a scope that contains no tests or nested scopes) is also a leaf node:
// One instance will be created for each empty scope describe("when 99 is added") { // A scope is "empty" and therefore a leaf node if it has no // tests or nested scopes, though it may have other code (which // will be executed in the instance created for that leaf node) buf += 99 }
The tests will be executed sequentially, in the order of appearance. The first test (or empty scope,
if that is first) will be executed when a class that mixes in PathAnyFunSpec
is
instantiated. Only the first test will be executed during this initial instance, and of course, only
the path to that test. Then, the first time the client uses the initial instance (by invoking one of run
,
expectedTestsCount
, tags
, or testNames
on the instance), the initial instance will,
before doing anything else, ensure that any remaining tests are executed, each in its own instance.
To ensure that the correct path is taken in each instance, and to register its test results, the initial
PathAnyFunSpec
instance must communicate with the other instances it creates for running any subsequent
leaf nodes. It does so by setting a thread-local variable prior to creating each instance (a technique
suggested by Esko Luontola). Each instance
of PathAnyFunSpec
checks the thread-local variable. If the thread-local is not set, it knows it
is an initial instance and therefore executes every block it encounters until it discovers, and executes the
first test (or empty scope, if that's the first leaf node). It then discovers, but does not execute the next
leaf node, or discovers there are no other leaf nodes remaining to execute. It communicates the path to the next
leaf node, if any, and the result of running the test it did execute, if any, back to the initial instance. The
initial instance repeats this process until all leaf nodes have been executed and all test results registered.
You mark a test as ignored in an org.scalatest.funspec.PathAnyFunSpec
in the same manner as in
an org.scalatest.funspec.AnyFunSpec
. Please see the Ignored tests section
in its documentation for more information.
Note that a separate instance will be created for an ignored test,
and the path to the ignored test will be executed in that instance, but the test function itself will not
be executed. Instead, a TestIgnored
event will be fired.
You output information using Informer
s in an org.scalatest.funspec.PathAnyFunSpec
in the same manner
as in an org.scalatest.funspec.AnyFunSpec
. Please see the Informers
section in its documentation for more information.
You mark a test as pending in an org.scalatest.funspec.PathAnyFunSpec
in the same manner as in
an org.scalatest.funspec.AnyFunSpec
. Please see the Pending tests
section in its documentation for more information.
Note that a separate instance will be created for a pending test,
and the path to the ignored test will be executed in that instance, as well as the test function (up until it
completes abruptly with a TestPendingException
).
You can place tests into groups by tagging them in an org.scalatest.funspec.PathAnyFunSpec
in the same manner
as in an org.scalatest.funspec.AnyFunSpec
. Please see the Tagging tests
section in its documentation for more information.
Note that one difference between this class and its sister class
org.scalatest.funspec.AnyFunSpec
is that because tests are executed at construction time, rather than each
time run is invoked, an org.scalatest.funspec.PathAnyFunSpec
will always execute all non-ignored tests. When
run
is invoked on a PathAnyFunSpec
, if some tests are excluded based on tags, the registered
results of running those tests will not be reported. (But those tests will have already run and the results
registered.) By contrast, because an org.scalatest.funspec.AnyFunSpec
only executes tests after run
has been called, and at that time the tags to include and exclude are known, only tests selected by the tags
will be executed.
In short, in an org.scalatest.funspec.AnyFunSpec
, tests not selected by the tags to include
and exclude specified for the run (via the Filter
passed to run
) will not be executed.
In an org.scalatest.funspec.PathAnyFunSpec
, by contrast, all non-ignored tests will be executed, each
during the construction of its own instance, and tests not selected by the tags to include and exclude specified
for a run will not be reported. (One upshot of this is that if you have tests that you want to tag as being slow so
you can sometimes exclude them during a run, you probably don't want to put them in a PathAnyFunSpec
. Because
in a path.Freespec
the slow tests will be run regardless, with only their registered results not being reported
if you exclude slow tests during a run.)
You can factor out shared tests in an org.scalatest.funspec.PathAnyFunSpec
in the same manner as in
an org.scalatest.funspec.AnyFunSpec
. Please see the Shared tests
section in its documentation for more information.
Nested suites are not allowed in a PathAnyFunSpec
. Because
a PathAnyFunSpec
executes tests eagerly at construction time, registering the results of those test runs
and reporting them later when run
is invoked, the order of nested suites versus test runs would be
different in a org.scalatest.funspec.PathAnyFunSpec
than in an org.scalatest.funspec.AnyFunSpec
. In
org.scalatest.funspec.AnyFunSpec
's implementation of run
, nested suites are executed then tests
are executed. A org.scalatest.funspec.PathAnyFunSpec
with nested suites would execute these in the opposite
order: first tests then nested suites. To help make PathAnyFunSpec
code easier to
reason about by giving readers of one less difference to think about, nested suites are not allowed. If you want
to add nested suites to a PathAnyFunSpec
, you can instead wrap them all in a
Suites
object. They will
be executed in the order of appearance (unless a Distributor is passed, in which case
they will execute in parallel).
Many ScalaTest events include a duration that indicates how long the event being reported took to execute. For
example, a TestSucceeded
event provides a duration indicating how long it took for that test
to execute. A SuiteCompleted
event provides a duration indicating how long it took for that entire
suite of tests to execute.
In the test completion events fired by a PathAnyFunSpec
(TestSucceeded
,
TestFailed
, or TestPending
), the durations reported refer
to the time it took for the tests to run. This time is registered with the test results and reported along
with the test results each time run
is invoked.
By contrast, the suite completion events fired for a PathAnyFunSpec
represent the amount of time
it took to report the registered results. (These events are not fired by PathAnyFunSpec
, but instead
by the entity that invokes run
on the PathAnyFunSpec
.) As a result, the total time
for running the tests of a PathAnyFunSpec
, calculated by summing the durations of all the individual
test completion events, may be greater than the duration reported for executing the entire suite.
Implementation trait for class Path.FunSpec
, which is
a sister class to org.scalatest.funspec.AnyFunSpec
that isolates
tests by running each test in its own instance of the test class,
and for each test, only executing the path leading to that test.
Implementation trait for class Path.FunSpec
, which is
a sister class to org.scalatest.funspec.AnyFunSpec
that isolates
tests by running each test in its own instance of the test class,
and for each test, only executing the path leading to that test.
PathAnyFunSpec
is a class, not a trait,
to minimize compile time given there is a slight compiler overhead to
mixing in traits compared to extending classes. If you need to mix the
behavior of PathAnyFunSpec
into some other class, you can use this
trait instead, because class PathAnyFunSpec
does nothing more than
extend this trait and add a nice toString
implementation.
See the documentation of the class for a detailed
overview of PathAnyFunSpec
.
Classes and traits for ScalaTest's
FunSpec
style.This package is released as the
scalatest-funspec
module.