A suite of tests in which each test represents one scenario of a feature.
A suite of tests in which each test represents one scenario of a feature.
AnyFeatureSpec
is intended for writing tests that are "higher level" than unit tests, for example, integration
tests, functional tests, and acceptance tests. You can use AnyFeatureSpec
for unit testing if you prefer, however.
Recommended Usage:
Class AnyFeatureSpec is primarily intended for acceptance testing, including facilitating the process of programmers working alongside non-programmers to
define the acceptance requirements.
|
Although not required, AnyFeatureSpec
is often used together with GivenWhenThen
to express acceptance requirements
in more detail. Here's an example:
package org.scalatest.examples.featurespec import org.scalatest._ class TVSet { private var on: Boolean = false def isOn: Boolean = on def pressPowerButton() { on = !on } } class TVSetSpec extends featurespec.AnyFeatureSpec with GivenWhenThen { info("As a TV set owner") info("I want to be able to turn the TV on and off") info("So I can watch TV when I want") info("And save energy when I'm not watching TV") Feature("TV power button") { Scenario("User presses power button when TV is off") { Given("a TV set that is switched off") val tv = new TVSet assert(!tv.isOn) When("the power button is pressed") tv.pressPowerButton() Then("the TV should switch on") assert(tv.isOn) } Scenario("User presses power button when TV is on") { Given("a TV set that is switched on") val tv = new TVSet tv.pressPowerButton() assert(tv.isOn) When("the power button is pressed") tv.pressPowerButton() Then("the TV should switch off") assert(!tv.isOn) } } }
Note: for more information on the calls to Given
, When
, and Then
, see the documentation
for trait GivenWhenThen
and the Informers
section below.
A AnyFeatureSpec
contains feature clauses and scenarios. You define a feature clause
with feature
, and a scenario with scenario
. Both
feature
and scenario
are methods, defined in
AnyFeatureSpec
, which will be invoked
by the primary constructor of TVSetSpec
.
A feature clause describes a feature of the subject (class or other entity) you are specifying
and testing. In the previous example,
the subject under specification and test is a TV set. The feature being specified and tested is
the behavior of a TV set when its power button is pressed. With each scenario you provide a
string (the spec text) that specifies the behavior of the subject for
one scenario in which the feature may be used, 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
scenario
, which will register the test for later execution.
A AnyFeatureSpec
'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.
Scenarios can only be registered with the scenario
method while the AnyFeatureSpec
is
in its registration phase. Any attempt to register a scenario after the AnyFeatureSpec
has
entered its ready phase, i.e., after run
has been invoked on the AnyFeatureSpec
,
will be met with a thrown TestRegistrationClosedException
. The recommended style
of using AnyFeatureSpec
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
.
Each scenario represents one test. The name of the test is the spec text passed to the scenario
method.
The feature name does not appear as part of the test name. In a AnyFeatureSpec
, therefore, you must take care
to ensure that each test has a unique name (in other words, that each scenario
has unique spec text).
When you run a AnyFeatureSpec
, 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 TVSetSpec
from within the Scala interpreter:
scala> org.scalatest.run(new TVSetSpec)
You would see:
TVSetSpec:
As a TV set owner
I want to be able to turn the TV on and off
So I can watch TV when I want
And save energy when I'm not watching TV
Feature: TV power button
Scenario: User presses power button when TV is off
Given a TV set that is switched off
When the power button is pressed
Then the TV should switch on
Scenario: User presses power button when TV is on
Given a TV set that is switched on
When the power button is pressed
Then the TV should switch off
Or, to run just the “Feature: TV power button Scenario: User presses power button when TV is on
” method, you could pass that test's name, or any unique substring of the
name, such as "TV is on"
. Here's an example:
scala> org.scalatest.run(new TVSetSpec, "TV is on")
TVSetSpec:
As a TV set owner
I want to be able to turn the TV on and off
So I can watch TV when I want
And save energy when I'm not watching TV
Feature: TV power button
Scenario: User presses power button when TV is on
Given a TV set that is switched on
When the power button is pressed
Then the TV should switch off
Note: Trait AnyFeatureSpec
's syntax is in part inspired by Cucumber, 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, AnyFeatureSpec
provides registration
methods that start with ignore
instead of scenario
. For example, to temporarily
disable the test named addition
, just change “scenario
” into “ignore
,” like this:
package org.scalatest.examples.featurespec.ignore import org.scalatest.featurespec.AnyFeatureSpec class TVSet { private var on: Boolean = false def isOn: Boolean = on def pressPowerButton() { on = !on } } class TVSetSpec extends AnyFeatureSpec { Feature("TV power button") { ignore("User presses power button when TV is off") { val tv = new TVSet assert(!tv.isOn) tv.pressPowerButton() assert(tv.isOn) } Scenario("User presses power button when TV is on") { val tv = new TVSet tv.pressPowerButton() assert(tv.isOn) tv.pressPowerButton() assert(!tv.isOn) } } }
If you run this version of SetSpec
with:
scala> org.scalatest.run(new TVSetSpec)
It will run only the second scenario and report that the first scenario was ignored:
TVSetSpec: Feature: TV power button Scenario: User presses power button when TV is off !!! IGNORED !!! Scenario: User presses power button when TV is on
One of the parameters to AnyFeatureSpec
'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 default reporting done by AnyFeatureSpec
'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 scenario to the reporter. For example,
the GivenWhenThen
trait provides methods that use the implicit info
provided by AnyFeatureSpec
to pass such information to the reporter. You can see this in action in the initial example of this trait's documentation.
AnyFeatureSpec
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 FlatSpec
that uses markup
:
package org.scalatest.examples.featurespec.markup import collection.mutable import org.scalatest._ class SetSpec extends featurespec.AnyFeatureSpec 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. """ } Feature("An element can be added to an empty mutable Set") { Scenario("When an element is added to an empty mutable Set") { 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.featurespec.note import collection.mutable import org.scalatest._ class SetSpec extends featurespec.AnyFeatureSpec { Feature("An element can be added to an empty mutable Set") { Scenario("When an element is added to an empty mutable Set") { 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: Feature: An element can be added to an empty mutable Set + notes are sent immediately + alerts are also sent immediately Scenario: When an element is added to an empty mutable Set 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 tests as pending in a AnyFeatureSpec
like this:
package org.scalatest.examples.featurespec.pending import org.scalatest.featurespec.AnyFeatureSpec class TVSet { private var on: Boolean = false def isOn: Boolean = on def pressPowerButton() { on = !on } } class TVSetSpec extends AnyFeatureSpec { Feature("TV power button") { Scenario("User presses power button when TV is off") (pending) Scenario("User presses power button when TV is on") { val tv = new TVSet tv.pressPowerButton() assert(tv.isOn) tv.pressPowerButton() assert(!tv.isOn) } } }
(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 TVSetSpec
with:
scala> org.scalatest.run(new TVSetSpec)
It will run both tests, but report that When empty should have size 0
is pending. You'll see:
TVSetSpec: Feature: TV power button Scenario: User presses power button when TV is off (pending) Scenario: User presses power button when TV is on
One difference between an ignored test and a pending one is that an ignored test is intended to be used during a significant refactorings of the code under test, when tests break and you don't want to spend the time to fix all of them immediately. You can mark some of those broken tests as ignored temporarily, so that you can focus the red bar on just failing tests you actually want to fix immediately. Later you can go back and fix the ignored tests. In other words, by ignoring some failing tests temporarily, you can more easily notice failed tests that you actually want to fix. By contrast, a pending test is intended to be used before a test and/or the code under test is written. Pending indicates you've decided to write a test for a bit of behavior, but either you haven't written the test yet, or have only written part of it, or perhaps you've written the test but don't want to implement the behavior it tests until after you've implemented a different bit of behavior you realized you need first. Thus ignored tests are designed to facilitate refactoring of existing code whereas pending tests are designed to facilitate the creation of new code.
One other difference between ignored and pending tests is that ignored tests are implemented as a test tag that is
excluded by default. Thus an ignored test is never executed. By contrast, a pending test is implemented as a
test that throws TestPendingException
(which is what calling the pending
method does). Thus
the body of pending tests are executed up until they throw TestPendingException
. The reason for this difference
is that it enables your unfinished test to send InfoProvided
messages to the reporter before it completes
abruptly with TestPendingException
, as shown in the previous example on Informer
s
that used the GivenWhenThen
trait. For example, the following snippet in a AnyFeatureSpec
:
package org.scalatest.examples.featurespec.infopending import org.scalatest._ class TVSet { private var on: Boolean = false def isOn: Boolean = on def pressPowerButton() { on = !on } } class TVSetSpec extends featurespec.AnyFeatureSpec with GivenWhenThen { info("As a TV set owner") info("I want to be able to turn the TV on and off") info("So I can watch TV when I want") info("And save energy when I'm not watching TV") Feature("TV power button") { Scenario("User presses power button when TV is off") { Given("a TV that is switched off") When("the power button is pressed") Then("the TV should switch on") pending } Scenario("User presses power button when TV is on") { Given("a TV that is switched on") When("the power button is pressed") Then("the TV should switch off") pending } } }
Would yield the following output when run in the interpreter:
scala> org.scalatest.run(new TVSetSpec) TVSetSpec: As a TV set owner I want to be able to turn the TV on and off So I can watch TV when I want And save energy when I'm not watching TV Feature: TV power button Scenario: User presses power button when TV is off (pending) Given a TV that is switched off When the power button is pressed Then the TV should switch on Scenario: User presses power button when TV is on (pending) Given a TV that is switched on When the power button is pressed Then the TV should switch off
A AnyFeatureSpec
's tests may be classified into groups by tagging them with string names.
As with any suite, when executing a AnyFeatureSpec
, groups of tests can
optionally be included and/or excluded. To tag a AnyFeatureSpec
'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 AnyFeatureSpec
s like this:
package org.scalatest.examples.featurespec.tagging import org.scalatest.Tag object DbTest extends Tag("com.mycompany.tags.DbTest")
Given these definitions, you could place AnyFeatureSpec
tests into groups with tags like this:
import org.scalatest.featurespec.AnyFeatureSpec import org.scalatest.tagobjects.Slow class TVSet { private var on: Boolean = false def isOn: Boolean = on def pressPowerButton() { on = !on } } class TVSetSpec extends AnyFeatureSpec { Feature("TV power button") { Scenario("User presses power button when TV is off", Slow) { val tv = new TVSet assert(!tv.isOn) tv.pressPowerButton() assert(tv.isOn) } Scenario("User presses power button when TV is on", Slow, DbTest) { val tv = new TVSet tv.pressPowerButton() assert(tv.isOn) tv.pressPowerButton() assert(!tv.isOn) } } }
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 AnyFeatureSpec
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 a holder object containing multiple fixture objects) each time it is called. You can call a get-fixture method at the beginning of each test that needs the fixture, storing the returned object or objects in local variables. Here's an example:
package org.scalatest.examples.featurespec.getfixture import org.scalatest.featurespec.AnyFeatureSpec import collection.mutable.ListBuffer class ExampleSpec extends AnyFeatureSpec { class Fixture { val builder = new StringBuilder("ScalaTest is designed to ") val buffer = new ListBuffer[String] } def fixture = new Fixture Feature("Simplicity") { Scenario("User needs to read test code written by others") { val f = fixture f.builder.append("encourage clear code!") assert(f.builder.toString === "ScalaTest is designed to encourage clear code!") assert(f.buffer.isEmpty) f.buffer += "sweet" } Scenario("User needs to understand what the tests are doing") { val f = fixture f.builder.append("be easy to reason about!") assert(f.builder.toString === "ScalaTest is designed to be easy to reason about!") 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.
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.featurespec.fixturecontext import collection.mutable.ListBuffer import org.scalatest.featurespec.AnyFeatureSpec class ExampleSpec extends AnyFeatureSpec { trait Builder { val builder = new StringBuilder("ScalaTest is designed to ") } trait Buffer { val buffer = ListBuffer("ScalaTest", "is", "designed", "to") } Feature("Simplicity") { // This test needs the StringBuilder fixture Scenario("User needs to read test code written by others") { new Builder { builder.append("encourage clear code!") assert(builder.toString === "ScalaTest is designed to encourage clear code!") } } // This test needs the ListBuffer[String] fixture Scenario("User needs to understand what the tests are doing") { new Buffer { buffer += ("be", "easy", "to", "reason", "about!") assert(buffer === List("ScalaTest", "is", "designed", "to", "be", "easy", "to", "reason", "about!")) } } // This test needs both the StringBuilder and ListBuffer Scenario("User needs to write tests") { new Builder with Buffer { builder.append("be easy to learn!") buffer += ("be", "easy", "to", "remember", "how", "to", "write!") assert(builder.toString === "ScalaTest is designed to be easy to learn!") assert(buffer === List("ScalaTest", "is", "designed", "to", "be", "easy", "to", "remember", "how", "to", "write!")) } } } }
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. That is to say, 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.featurespec.noargtest import java.io.File import org.scalatest._ class ExampleSpec extends featurespec.AnyFeatureSpec { 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 } } Scenario("This scenario should succeed") { assert(1 + 1 === 2) } Scenario("This scenario 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 ExampleSpec) ExampleSpec: Scenario: This scenario should succeed Scenario: This scenario should fail *** FAILED *** 2 did not equal 3 (:115) + 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.featurespec.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.featurespec.AnyFeatureSpec import DbServer._ import java.util.UUID.randomUUID import java.io._ class ExampleSpec extends AnyFeatureSpec { def withDatabase(testCode: Db => Any) { val dbName = randomUUID.toString val db = createDb(dbName) // create the fixture try { db.append("ScalaTest is designed to ") // 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 designed to ") // set up the fixture testCode(file, writer) // "loan" the fixture to the test } finally writer.close() // clean up the fixture } Feature("Simplicity") { // This test needs the file fixture Scenario("User needs to read test code written by others") { withFile { (file, writer) => writer.write("encourage clear code!") writer.flush() assert(file.length === 46) } } // This test needs the database fixture Scenario("User needs to understand what the tests are doing") { withDatabase { db => db.append("be easy to reason about!") assert(db.toString === "ScalaTest is designed to be easy to reason about!") } } // This test needs both the file and the database Scenario("User needs to write tests") { withDatabase { db => withFile { (file, writer) => // loan-fixture methods compose db.append("be easy to learn!") writer.write("be easy to remember how to write!") writer.flush() assert(db.toString === "ScalaTest is designed to be easy to learn!") assert(file.length === 58) } } } } }
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 FixtureAnyFeatureSpec
and overriding withFixture(OneArgTest)
.
Each test in a FixtureAnyFeatureSpec
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.featurespec.oneargtest import org.scalatest.featurespec import java.io._ class ExampleSpec extends featurespec.FixtureAnyFeatureSpec { 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 designed to be ") // set up the fixture withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test } finally writer.close() // clean up the fixture } Feature("Simplicity") { Scenario("User needs to read test code written by others") { f => f.writer.write("encourage clear code!") f.writer.flush() assert(f.file.length === 49) } Scenario("User needs to understand what the tests are doing") { f => f.writer.write("be easy to reason about!") f.writer.flush() assert(f.file.length === 52) } } }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 FixtureAnyFeatureSpec
.
==== 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.featurespec.beforeandafter import org.scalatest._ import collection.mutable.ListBuffer class ExampleSpec extends featurespec.AnyFeatureSpec with BeforeAndAfter { val builder = new StringBuilder val buffer = new ListBuffer[String] before { builder.append("ScalaTest is designed to ") } after { builder.clear() buffer.clear() } Feature("Simplicity") { Scenario("User needs to read test code written by others") { builder.append("encourage clear code!") assert(builder.toString === "ScalaTest is designed to encourage clear code!") assert(buffer.isEmpty) buffer += "sweet" } Scenario("User needs to understand what the tests are doing") { builder.append("be easy to reason about!") assert(builder.toString === "ScalaTest is designed to be easy to reason about!") 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.
== 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.featurespec.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 designed to ") 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 featurespec.AnyFeatureSpec with Builder with Buffer { Feature("Simplicity") { Scenario("User needs to read test code written by others") { builder.append("encourage clear code!") assert(builder.toString === "ScalaTest is designed to encourage clear code!") assert(buffer.isEmpty) buffer += "clear" } Scenario("User needs to understand what the tests are doing") { builder.append("be easy to reason about!") assert(builder.toString === "ScalaTest is designed to be easy to reason about!") assert(buffer.isEmpty) buffer += "easy" } } }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 AnyFeatureSpec with Buffer with BuilderAnd if you only need one fixture you mix in only that trait:
class Example3Spec extends AnyFeatureSpec with BuilderAnother 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.featurespec.composingbeforeandaftereach import org.scalatest._ import collection.mutable.ListBuffer trait Builder extends BeforeAndAfterEach { this: Suite => val builder = new StringBuilder override def beforeEach() { builder.append("ScalaTest is designed to ") 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 featurespec.AnyFeatureSpec with Builder with Buffer { Feature("Simplicity") { Scenario("User needs to read test code written by others") { builder.append("encourage clear code!") assert(builder.toString === "ScalaTest is designed to encourage clear code!") assert(buffer.isEmpty) buffer += "clear" } Scenario("User needs to understand what the tests are doing") { builder.append("be easy to reason about!") assert(builder.toString === "ScalaTest is designed to be easy to reason about!") assert(buffer.isEmpty) buffer += "easy" } } }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 scenarios ==
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 AnyFeatureSpec
, you first place shared tests (i.e., shared scenarios) in
behavior functions. These behavior functions will be
invoked during the construction phase of any AnyFeatureSpec
that uses them, so that the scenarios they contain will
be registered as scenarios in that AnyFeatureSpec
.
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 scenarios that make sense any time the stack is non-empty. Thus you'd ideally want to run
those same scenarios 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 scenarios out into a behavior function, into which you pass the
stack fixture to use when running the tests. So in your AnyFeatureSpec
for stack, you'd invoke the
behavior function three times, passing in each of the three stack fixtures so that the shared scenarios are run for all three fixtures.
You can define a behavior function that encapsulates these shared scenarios inside the AnyFeatureSpec
that uses them. If they are shared
between different AnyFeatureSpec
s, however, you could also define them in a separate trait that is mixed into
each AnyFeatureSpec
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 scenarios for non-full stacks:
import org.scalatest.featurespec.AnyFeatureSpec import org.scalatest.GivenWhenThen import org.scalatestexamples.helpers.Stack trait FeatureSpecStackBehaviors { this: AnyFeatureSpec with GivenWhenThen => def nonEmptyStack(createNonEmptyStack: => Stack[Int], lastItemAdded: Int) { Scenario("empty is invoked on this non-empty stack: " + createNonEmptyStack.toString) { Given("a non-empty stack") val stack = createNonEmptyStack When("empty is invoked on the stack") Then("empty returns false") assert(!stack.empty) } Scenario("peek is invoked on this non-empty stack: " + createNonEmptyStack.toString) { Given("a non-empty stack") val stack = createNonEmptyStack val size = stack.size When("peek is invoked on the stack") Then("peek returns the last item added") assert(stack.peek === lastItemAdded) And("the size of the stack is the same as before") assert(stack.size === size) } Scenario("pop is invoked on this non-empty stack: " + createNonEmptyStack.toString) { Given("a non-empty stack") val stack = createNonEmptyStack val size = stack.size When("pop is invoked on the stack") Then("pop returns the last item added") assert(stack.pop === lastItemAdded) And("the size of the stack one less than before") assert(stack.size === size - 1) } } def nonFullStack(createNonFullStack: => Stack[Int]) { Scenario("full is invoked on this non-full stack: " + createNonFullStack.toString) { Given("a non-full stack") val stack = createNonFullStack When("full is invoked on the stack") Then("full returns false") assert(!stack.full) } Scenario("push is invoked on this non-full stack: " + createNonFullStack.toString) { Given("a non-full stack") val stack = createNonFullStack val size = stack.size When("push is invoked on the stack") stack.push(7) Then("the size of the stack is one greater than before") assert(stack.size === size + 1) And("the top of the stack contains the pushed value") assert(stack.peek === 7) } } }Given these behavior functions, you could invoke them directly, but
AnyFeatureSpec
offers a DSL for the purpose,
which looks like this:
ScenariosFor(nonEmptyStack(stackWithOneItem, lastValuePushed)) ScenariosFor(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:
ScenariosFor(nonEmptyStack) // assuming lastValuePushed is also in scope inside nonEmptyStack ScenariosFor(nonFullStack)The recommended style, however, is the functional, pass-all-the-needed-values-in style. Here's an example:
import org.scalatest.featurespec.AnyFeatureSpec import org.scalatest.GivenWhenThen import org.scalatestexamples.helpers.Stack class StackFeatureSpec extends AnyFeatureSpec with GivenWhenThen with FeatureSpecStackBehaviors { // 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 Feature("A Stack is pushed and popped") { Scenario("empty is invoked on an empty stack") { Given("an empty stack") val stack = emptyStack When("empty is invoked on the stack") Then("empty returns true") assert(stack.empty) } Scenario("peek is invoked on an empty stack") { Given("an empty stack") val stack = emptyStack When("peek is invoked on the stack") Then("peek throws IllegalStateException") assertThrows[IllegalStateException] { stack.peek } } Scenario("pop is invoked on an empty stack") { Given("an empty stack") val stack = emptyStack When("pop is invoked on the stack") Then("pop throws IllegalStateException") assertThrows[IllegalStateException] { emptyStack.pop } } ScenariosFor(nonEmptyStack(stackWithOneItem, lastValuePushed)) ScenariosFor(nonFullStack(stackWithOneItem)) ScenariosFor(nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed)) ScenariosFor(nonFullStack(stackWithOneItemLessThanCapacity)) Scenario("full is invoked on a full stack") { Given("an full stack") val stack = fullStack When("full is invoked on the stack") Then("full returns true") assert(stack.full) } ScenariosFor(nonEmptyStack(fullStack, lastValuePushed)) Scenario("push is invoked on a full stack") { Given("an full stack") val stack = fullStack When("push is invoked on the stack") Then("push throws IllegalStateException") assertThrows[IllegalStateException] { stack.push(10) } } } }If you load these classes into the Scala interpreter (with scalatest's JAR file on the class path), and execute it, you'll see:
scala> (new StackFeatureSpec).execute()
Feature: A Stack is pushed and popped
Scenario: empty is invoked on an empty stack
Given an empty stack
When empty is invoked on the stack
Then empty returns true
Scenario: peek is invoked on an empty stack
Given an empty stack
When peek is invoked on the stack
Then peek throws IllegalStateException
Scenario: pop is invoked on an empty stack
Given an empty stack
When pop is invoked on the stack
Then pop throws IllegalStateException
Scenario: empty is invoked on this non-empty stack: Stack(9)
Given a non-empty stack
When empty is invoked on the stack
Then empty returns false
Scenario: peek is invoked on this non-empty stack: Stack(9)
Given a non-empty stack
When peek is invoked on the stack
Then peek returns the last item added
And the size of the stack is the same as before
Scenario: pop is invoked on this non-empty stack: Stack(9)
Given a non-empty stack
When pop is invoked on the stack
Then pop returns the last item added
And the size of the stack one less than before
Scenario: full is invoked on this non-full stack: Stack(9)
Given a non-full stack
When full is invoked on the stack
Then full returns false
Scenario: push is invoked on this non-full stack: Stack(9)
Given a non-full stack
When push is invoked on the stack
Then the size of the stack is one greater than before
And the top of the stack contains the pushed value
Scenario: empty is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
Given a non-empty stack
When empty is invoked on the stack
Then empty returns false
Scenario: peek is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
Given a non-empty stack
When peek is invoked on the stack
Then peek returns the last item added
And the size of the stack is the same as before
Scenario: pop is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
Given a non-empty stack
When pop is invoked on the stack
Then pop returns the last item added
And the size of the stack one less than before
Scenario: full is invoked on this non-full stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
Given a non-full stack
When full is invoked on the stack
Then full returns false
Scenario: push is invoked on this non-full stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
Given a non-full stack
When push is invoked on the stack
Then the size of the stack is one greater than before
And the top of the stack contains the pushed value
Scenario: full is invoked on a full stack
Given an full stack
When full is invoked on the stack
Then full returns true
Scenario: empty is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
Given a non-empty stack
When empty is invoked on the stack
Then empty returns false
Scenario: peek is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
Given a non-empty stack
When peek is invoked on the stack
Then peek returns the last item added
And the size of the stack is the same as before
Scenario: pop is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
Given a non-empty stack
When pop is invoked on the stack
Then pop returns the last item added
And the size of the stack one less than before
Scenario: push is invoked on a full stack
Given an full stack
When push is invoked on the stack
Then push throws IllegalStateException
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.
Although in a AnyFeatureSpec
, the feature
clause is a nesting construct analogous to
FunSpec
's describe
clause, you many sometimes need to do a bit of
extra work to ensure that the test names are unique. If a duplicate test name problem shows up in a
AnyFeatureSpec
, you can pass in a prefix or suffix string to add to each test name. You can pass this string
the same way you pass any other data needed by the shared tests, or just call toString
on the shared fixture object.
This is the approach taken by the previous AnyFeatureSpecStackBehaviors
example.
Given this AnyFeatureSpecStackBehaviors
trait, calling it with the stackWithOneItem
fixture, like this:
ScenariosFor(nonEmptyStack(stackWithOneItem, lastValuePushed))yields test names: -
empty is invoked on this non-empty stack: Stack(9)
- peek is invoked on this non-empty stack: Stack(9)
- pop is invoked on this non-empty stack: Stack(9)
Whereas calling it with the stackWithOneItemLessThanCapacity
fixture, like this:
ScenariosFor(nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed))yields different test names: -
empty is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
- peek is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
- pop is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
Implementation trait for class AnyFeatureSpec
, which represents
a suite of tests in which each test represents one scenario of a
feature.
Implementation trait for class AnyFeatureSpec
, which represents
a suite of tests in which each test represents one scenario of a
feature.
AnyFeatureSpec
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 AnyFeatureSpec
into some other class, you can use this
trait instead, because class AnyFeatureSpec
does nothing more than
extend this trait and add a nice toString
implementation.
See the documentation of the class for a detailed
overview of AnyFeatureSpec
.
A sister class to org.scalatest.featurespec.AnyFeatureSpec
that can pass a fixture object into its tests.
A sister class to org.scalatest.featurespec.AnyFeatureSpec
that can pass a fixture object into its tests.
Recommended Usage:
Use class FixtureAnyFeatureSpec in situations for which AnyFeatureSpec
would be a good choice, when all or most tests need the same fixture objects
that must be cleaned up afterwards. Note: FixtureAnyFeatureSpec is intended for use in special situations, with class AnyFeatureSpec used for general needs. For
more insight into where FixtureAnyFeatureSpec fits in the big picture, see the withFixture(OneArgTest) subsection of the Shared fixtures section in the documentation for class AnyFeatureSpec .
|
Class FixtureAnyFeatureSpec
behaves similarly to class org.scalatest.featurespec.AnyFeatureSpec
, 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 trait also has 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.featurespec.AnyFeatureSpec
:
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.featurespec.oneargtest import org.scalatest.featurespec import java.io._ class ExampleSpec extends featurespec.FixtureAnyFeatureSpec { 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 designed to be ") // set up the fixture withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test } finally writer.close() // clean up the fixture } Feature("Simplicity") { Scenario("User needs to read test code written by others") { f => f.writer.write("encourage clear code!") f.writer.flush() assert(f.file.length === 49) } Scenario("User needs to understand what the tests are doing") { f => f.writer.write("be easy to reason about!") f.writer.flush() assert(f.file.length === 52) } } }
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.featurespec.sharing import java.util.concurrent.ConcurrentHashMap import org.scalatest.featurespec 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 featurespec.FixtureAnyFeatureSpec with DbFixture { override def populateDb(db: Db) { // setup the fixture db.append("ScalaTest is designed to ") } Feature("Simplicity") { Scenario("User needs to read test code written by others") { db => db.append("encourage clear code!") assert(db.toString === "ScalaTest is designed to encourage clear code!") } Scenario("User needs to understand what the tests are doing") { db => db.append("be easy to reason about!") assert(db.toString === "ScalaTest is designed to be easy to reason about!") } Scenario("User needs to write tests") { () => val buf = new StringBuffer buf.append("ScalaTest is designed to be ") buf.append("easy to learn!") assert(buf.toString === "ScalaTest is designed to be easy to learn!") } } }
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 FixtureAnyFeatureSpec
, which is
a sister class to org.scalatest.featurespec.AnyFeatureSpec
that can pass a
fixture object into its tests.
Implementation trait for class FixtureAnyFeatureSpec
, which is
a sister class to org.scalatest.featurespec.AnyFeatureSpec
that can pass a
fixture object into its tests.
FixtureAnyFeatureSpec
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 FixtureAnyFeatureSpec
into some other
class, you can use this trait instead, because class
FixtureAnyFeatureSpec
does nothing more than extend this trait and add a nice toString
implementation.
See the documentation of the class for a detailed
overview of FixtureAnyFeatureSpec
.
Classes and traits for ScalaTest's
FeatureSpec
style.This package is released as the
scalatest-featurespec
module.