A suite of property-based tests.
Implementation trait for class AnyPropSpec
, which represents
a suite of property-based tests.
Implementation trait for class AnyPropSpec
, which represents
a suite of property-based tests.
AnyPropSpec
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 AnyPropSpec
into some other class, you can use this
trait instead, because class AnyPropSpec
does nothing more than
extend this trait and add a nice toString
implementation.
See the documentation of the class for a detailed
overview of AnyPropSpec
.
A sister class to org.scalatest.propspec.AnyPropSpec
that can pass a fixture object into its tests.
A sister class to org.scalatest.propspec.AnyPropSpec
that can pass a fixture object into its tests.
Recommended Usage:
Use class FixtureAnyPropSpec in situations for which AnyPropSpec
would be a good choice, when all or most tests need the same fixture objects
that must be cleaned up afterwards. Note: FixtureAnyPropSpec is intended for use in special
situations, with class AnyPropSpec used for general needs. For
more insight into where FixtureAnyPropSpec fits in the big picture, see
the withFixture(OneArgTest) subsection of
the Shared fixtures section in the documentation for class AnyPropSpec .
|
Class FixtureAnyPropSpec
behaves similarly to class org.scalatest.propspec.AnyPropSpec
, 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 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
, passing
in the test code to run via the OneArgTest
argument. The withFixture
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.propspec.AnyPropSpec
:
FixtureParam
withFixture(OneArgTest)
methodHere's an example:
package org.scalatest.examples.fixture.propspec import org.scalatest._ import prop.PropertyChecks import java.io._ class ExampleSpec extends propspec.FixtureAnyPropSpec with PropertyChecks with Matchers { // 1. define type FixtureParam type FixtureParam = FileReader // 2. define the withFixture method def withFixture(test: OneArgTest) = { val FileName = "TempFile.txt" // Set up the temp file needed by the test val writer = new FileWriter(FileName) try { writer.write("Hello, test!") } finally { writer.close() } // Create the reader needed by the test val reader = new FileReader(FileName) try { // Run the test using the temp file test(reader) } finally { // Close and delete the temp file reader.close() val file = new File(FileName) file.delete() } } // 3. write property-based tests that take a fixture parameter // (Hopefully less contrived than the examples shown here.) property("can read from a temp file") { reader => var builder = new StringBuilder var c = reader.read() while (c != -1) { builder.append(c.toChar) c = reader.read() } val fileContents = builder.toString forAll { (c: Char) => whenever (c != 'H') { fileContents should not startWith c.toString } } } property("can read the first char of the temp file") { reader => val firstChar = reader.read() forAll { (c: Char) => whenever (c != 'H') { c should not equal firstChar } } } // (You can also write tests that don't take a fixture parameter.) property("can write tests that don't take the fixture") { () => forAll { (i: Int) => i + i should equal (2 * i) } } }
Note: to run the examples on this page, you'll need to include ScalaCheck on the classpath in addition to ScalaTest.
In the previous example, withFixture
creates and initializes a temp file, then invokes the test function,
passing in a FileReader
connected to that file. In addition to setting up the fixture before a test,
the withFixture
method also cleans it up afterwards. If you need to do some clean up
that must happen 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 a test fails, the OneArgTest
function will result in a Failed wrapping the
exception describing the failure.
The reason you must perform cleanup in a finally
clause is that in case an exception propagates back through
withFixture
, the finally
clause will ensure the fixture cleanup happens as that exception
propagates back up the call stack to runTest
.
If a test doesn't need the fixture, you can indicate that by providing a no-arg instead of a one-arg function.
In other words, instead of starting your function literal
with something like “reader =>
”, you'd start it with “() =>
”, as is done
in the third test in the above example. For such tests, runTest
will not invoke withFixture(OneArgTest)
. It will instead directly invoke withFixture(NoArgTest)
.
If 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(builder: StringBuilder, buffer: ListBuffer[String])
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.fixture.propspec.multi import org.scalatest._ import prop.PropertyChecks import scala.collection.mutable.ListBuffer class ExampleSpec extends propspec.FixtureAnyPropSpec with PropertyChecks with Matchers { case class FixtureParam(builder: StringBuilder, buffer: ListBuffer[String]) def withFixture(test: OneArgTest) = { // Create needed mutable objects val stringBuilder = new StringBuilder("ScalaTest is ") val listBuffer = new ListBuffer[String] val theFixture = FixtureParam(stringBuilder, listBuffer) // Invoke the test function, passing in the mutable objects withFixture(test.toNoArgTest(theFixture)) } property("testing should be easy") { f => f.builder.append("easy!") assert(f.builder.toString === "ScalaTest is easy!") assert(f.buffer.isEmpty) val firstChar = f.builder(0) forAll { (c: Char) => whenever (c != 'S') { c should not equal firstChar } } f.buffer += "sweet" } property("testing should be fun") { f => f.builder.append("fun!") assert(f.builder.toString === "ScalaTest is fun!") assert(f.buffer.isEmpty) val firstChar = f.builder(0) forAll { (c: Char) => whenever (c != 'S') { c should not equal firstChar } } } }
Implementation trait for class FixtureAnyPropSpec
, which is
a sister class to org.scalatest.propspec.AnyPropSpec
that can pass a
fixture object into its tests.
Implementation trait for class FixtureAnyPropSpec
, which is
a sister class to org.scalatest.propspec.AnyPropSpec
that can pass a
fixture object into its tests.
FixtureAnyPropSpec
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 FixtureAnyPropSpec
into some other
class, you can use this trait instead, because class
FixtureAnyPropSpec
does nothing more than extend this trait and add a nice toString
implementation.
See the documentation of the class for a detailed
overview of FixtureAnyPropSpec
.
A suite of property-based tests.
AnyPropSpec
is a good fit for teams that want to write tests exclusively in terms of property checks, and is also a good choice for writing the occasional test matrix when a different style trait is chosen as the main unit testing style.Here's an example
AnyPropSpec
:You can run a
AnyPropSpec
by invokingexecute
on it. This method, which prints test results to the standard output, is intended to serve as a convenient way to run tests from within the Scala interpreter. For example, to runSetSpec
from within the Scala interpreter, you could write:And you would see:
SetSpec: - an empty Set should have size 0 - invoking head on an empty Set should produce NoSuchElementException
Or, to run just the “
an empty Set should have size 0
” method, 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 SetSpec, "size 0") SetSpec: - an empty Set 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 forexecute
(below) and the ScalaTest shell.The
execute
method invokes arun
method that takes two parameters. Thisrun
method, which actually executes the suite, will usually be invoked by a test runner, such asrun
,tools.Runner
, a build tool, or an IDE.“
property
” is a method, defined inAnyPropSpec
, which will be invoked by the primary constructor ofSetSpec
. You specify the name of the test as a string between the parentheses, and the test code itself between curly braces. The test code is a function passed as a by-name parameter toproperty
, which registers it for later execution.A
AnyPropSpec
's lifecycle has two phases: the registration phase and the ready phase. It starts in registration phase and enters ready phase the first timerun
is called on it. It then remains in ready phase for the remainder of its lifetime.Tests can only be registered with the
property
method while theAnyPropSpec
is in its registration phase. Any attempt to register a test after theAnyPropSpec
has entered its ready phase, i.e., afterrun
has been invoked on theAnyPropSpec
, will be met with a thrownTestRegistrationClosedException
. The recommended style of usingAnyPropSpec
is to register tests during object construction as is done in all the examples shown here. If you keep to the recommended style, you should never see aTestRegistrationClosedException
.Ignored tests
To support the common use case of temporarily disabling a test, with the good intention of resurrecting the test at a later time,
AnyPropSpec
provides registration methods that start withignore
instead ofproperty
. Here's an example:If you run this version of
SetSuite
with:It will run only the second test and report that the first test was ignored:
Informers
One of the parameters to
AnyPropSpec
'srun
method is aReporter
, which will collect and report information about the running suite of tests. Information about suites and tests that were run, whether tests succeeded or failed, and tests that were ignored will be passed to theReporter
as the suite runs. Most often the reporting done by default byAnyPropSpec
's methods will be sufficient, but occasionally you may wish to provide custom information to theReporter
from a test. For this purpose, anInformer
that will forward information to the currentReporter
is provided via theinfo
parameterless method. You can pass the extra information to theInformer
via itsapply
method. TheInformer
will then pass the information to theReporter
via anInfoProvided
event. Here's an example that shows both a direct use as well as an indirect use through the methods ofGivenWhenThen
:If you run this
AnyPropSpec
from the interpreter, you will see the following output:scala> org.scalatest.run(new SetSpec) SetSpec: - an element can be added to an empty mutable Set + ---------------- + Given an empty mutable BitSet + When an element is added + Then the Set should have size 1 + And the Set should contain the added element + ---------------- + Given an empty mutable HashSet + When an element is added + Then the Set should have size 1 + And the Set should contain the added element + ---------------- + Given an empty mutable LinkedHashSet + When an element is added + Then the Set should have size 1 + And the Set should contain the added element
Documenters
AnyPropSpec
also provides amarkup
method that returns aDocumenter
, which allows you to send to theReporter
text formatted in Markdown syntax. You can pass the extra information to theDocumenter
via itsapply
method. TheDocumenter
will then pass the information to theReporter
via anMarkupProvided
event.Here's an example
AnyPropSpec
that usesmarkup
: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 aboveSetSpec
would look like in the HTML reporter:Notifiers and alerters
ScalaTest records text passed to
info
andmarkup
during tests, and sends the recorded text in therecordedEvents
field of test completion events likeTestSucceeded
andTestFailed
. This allows string reporters (like the standard out reporter) to showinfo
andmarkup
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 theinfo
andmarkup
text in red. If a test succeeds, string reporters will show theinfo
andmarkup
text in green. While this approach helps the readability of reports, it means that you can't useinfo
to get status updates from long running tests.To get immediate (i.e., non-recorded) notifications from tests, you can use
note
(aNotifier
) andalert
(anAlerter
). Here's an example showing the differences:Because
note
andalert
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: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
andmarkup
for text that should form part of the specification output. Usenote
andalert
to send status notifications. (Because the HTML reporter is intended to produce a readable, printable specification,info
andmarkup
text will appear in the HTML report, butnote
andalert
text will not.)Pending tests
A pending test is one that has been given a name but is not yet implemented. The purpose of pending tests is to facilitate a style of testing in which documentation of behavior is sketched out before tests are written to verify that behavior (and often, before the behavior of the system being tested is itself implemented). Such sketches form a kind of specification of what tests and functionality to implement later.
To support this style of testing, a test can be given a name that specifies one bit of behavior required by the system being tested. The test can also include some code that sends more information about the behavior to the reporter when the tests run. At the end of the test, it can call method
pending
, which will cause it to complete abruptly withTestPendingException
.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. (The code of a pending test is executed just like any other test.) However, because the test completes abruptly withTestPendingException
, the test will be reported as pending, to indicate the actual test, and possibly the functionality, has not yet been implemented.You can mark tests pending in
AnyPropSpec
like this:(Note: "
(pending)
" is the body of the test. Thus the test contains just one statement, an invocation of thepending
method, which throwsTestPendingException
.) If you run this version ofSetSuite
with:It will run both tests, but report that first test is pending. You'll see:
One difference between an ignored test and a pending one is that an ignored test is intended to be used during a significant refactorings of the code under test, when tests break and you don't want to spend the time to fix all of them immediately. You can mark some of those broken tests as ignored temporarily, so that you can focus the red bar on just failing tests you actually want to fix immediately. Later you can go back and fix the ignored tests. In other words, by ignoring some failing tests temporarily, you can more easily notice failed tests that you actually want to fix. By contrast, a pending test is intended to be used before a test and/or the code under test is written. Pending indicates you've decided to write a test for a bit of behavior, but either you haven't written the test yet, or have only written part of it, or perhaps you've written the test but don't want to implement the behavior it tests until after you've implemented a different bit of behavior you realized you need first. Thus ignored tests are designed to facilitate refactoring of existing code whereas pending tests are designed to facilitate the creation of new code.
One other difference between ignored and pending tests is that ignored tests are implemented as a test tag that is excluded by default. Thus an ignored test is never executed. By contrast, a pending test is implemented as a test that throws
TestPendingException
(which is what calling thepending
method does). Thus the body of pending tests are executed up until they throwTestPendingException
. The reason for this difference is that it enables your unfinished test to sendInfoProvided
messages to the reporter before it completes abruptly withTestPendingException
, as shown in the previous example onInformer
s that used theGivenWhenThen
trait.Tagging tests
A
AnyPropSpec
's tests may be classified into groups by tagging them with string names. As with any suite, when executing aAnyPropSpec
, groups of tests can optionally be included and/or excluded. To tag aAnyPropSpec
's tests, you pass objects that extend classorg.scalatest.Tag
to methods that register tests. ClassTag
takes one parameter, a string name. If you have created tag annotation interfaces as described in theTag
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 theTag
constructor. For example, if you've defined a tag annotation interface with fully qualified names,com.mycompany.tags.DbTest
, then you could create a matching tag forAnyPropSpec
s like this:Given these definitions, you could place
AnyPropSpec
tests into groups with tags like this:This code marks both tests with the
org.scalatest.tags.Slow
tag, and the second test with thecom.mycompany.tags.DbTest
tag.The
run
method takes aFilter
, whose constructor takes an optionalSet[String]
calledtagsToInclude
and aSet[String]
calledtagsToExclude
. IftagsToInclude
isNone
, all tests will be run except those those belonging to tags listed in thetagsToExclude
Set
. IftagsToInclude
is defined, only tests belonging to tags mentioned in thetagsToInclude
set, and not mentioned intagsToExclude
, will be run.Shared fixtures
A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code.
ScalaTest recommends three techniques to eliminate such code duplication:
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 techniques in
AnyPropSpec
are identical to those inFunSuite
, but with “test
” replaced by “property
”. The following table summarizes the options with a link to the relevant documentation for traitFunSuite
:withFixture
when most or all tests need the same fixture.withFixture(NoArgTest)
withFixture(OneArgTest)
instead)withFixture(OneArgTest)
BeforeAndAfter
BeforeAndAfterEach
Using
AnyPropSpec
to implement a test matrixUsing fixture-context objects in a
AnyPropSpec
is a good way to implement a test matrix. What is the matrix? A test matrix is a series of tests that you need to run on a series of subjects. For example, The Scala API contains many implementations of traitSet
. Every implementation must obey the contract ofSet
. One property of anySet
is that an emptySet
should have size 0, another is that invoking head on an emptySet
should give you aNoSuchElementException
, and so on. Already you have a matrix, where rows are the properties and the columns are the set implementations:BitSet
HashSet
TreeSet
One way to implement this test matrix is to define a trait to represent the columns (in this case,
BitSet
,HashSet
, andTreeSet
) as elements in a single-dimensionalTable
. Each element in theTable
represents oneSet
implementation. Because different properties may require different fixture instances for those implementations, you can define a trait to hold the examples, like this:Given this trait, you could provide empty sets in one implementation of
SetExamples
, and non-empty sets in another. Here's how you might provide empty set examples:And here's how you might provide set examples with one item each:
Armed with these example classes, you can define checks of properties that require empty or non-empty set fixtures by using instances of these classes as fixture-context objects. In other words, the columns of the test matrix are implemented as elements of a one-dimensional table of fixtures, the rows are implemented as
property
clauses of aAnyPropSpec
.Here's a complete example that checks the two properties mentioned previously:
One benefit of this approach is that the compiler will help you when you need to add either a new row or column to the matrix. In either case, you'll need to ensure all cells are checked to get your code to compile.
Shared tests
Sometimes you may want to run the same test code on different fixture objects. That is to say, you may want to write tests that are "shared" by different fixture objects. You accomplish this in a
AnyPropSpec
in the same way you would do it in aFunSuite
, except instead oftest
you sayproperty
, and instead oftestsFor
you saypropertiesFor
. For more information, see the Shared tests section ofFunSuite
's documentation.