package scalamock
ScalaMock: Native Scala Mocking
To use ScalaMock, you need the relevant MockFactoryBase trait implementation:
- for ScalaTest, use org.scalamock.scalatest.MockFactory,
- for Specs2 use org.scalamock.specs2.IsolatedMockFactory or org.scalamock.specs2.MockContext
At present, ScalaMock can only mock traits, Java interfaces, and non-final classes that define a default constructor. A future version will be able to mock any class, and singleton/companion objects.
ScalaMock supports two different mocking styles - expectations first and record then verify. These styles can be mixed within a single test.
Expectations-First Style
In the expectations-first style, expectations are set on mock objects before exercising the system under test. If these expectations are not met, the test fails.
A mock function that supports this style is created with mockFunction. For
example, to create a mock function taking a single Int argument and
returning a String:
val m = mockFunction[Int, String]
A mock object that supports this style is created with mock. For example,
to create a mock that implements the Turtle trait:
val m = mock[Turtle]Expectations can then be set using expects:
(m.setPosition _).expects(10.0, 10.0) (m.forward _).expects(5.0) (m.getPosition _).expects().returning(15.0, 10.0) drawLine(m, (10.0, 10.0), (15.0, 10.0))
Record-then-Verify (Mockito) Style
In the record then verify style, expectations are verified after the system under test has executed.
A stub function that supports this style is created with stubFunction. For
example:
val m = stubFunction[Int, String]
A stub object that supports this style is created with stub. For example:
val m = stub[Turtle]Return values that are used by the system under test can be set up by using
when. Calls are verified using verify:
(m.getPosition _).when().returns(15.0, 10.0) drawLine(m, (10.0, 10.0), (15.0, 10.0)) (m.setPosition _).verify(10.0, 10.0) (m.forward _).verify(5.0)
Argument matching
ScalaMock supports two types of generalised matching: wildcards and epsilon matching.
Wildcards
Wildcard values are specified with an * (asterisk). For example:
m expects ("this", *)will match any of the following:
m("this", 42) m("this", 1.0) m("this", null)
Epsilon matching
Epsilon matching is useful when dealing with floating point values. An epsilon match is
specified with the ~ (tilde) operator:
m expects (~42.0)will match:
m(42.0) m(42.0001) m(41.9999)
but will not match:
m(43.0) m(42.1)
Repeated parameters
Repeated parameters are represented as a Seq. For example, given:
def takesRepeatedParameter(x: Int, ys: String*)
you can set an expectation with:
(m.takesRepeatedParameter _).expects(42, Seq("red", "green", "blue"))
Predicate matching
More complicated argument matching can be implemented by using where to
pass a predicate:
m = mockFunction[Double, Double, Unit] m expects (where { _ < _ })
Return values
By default mocks and stubs return null. You can return a computed return
value (or throw a computed exception) with onCall:
val mockIncrement = mockFunction[Int, Int] m expects (*) onCall { _ + 1 }
Overloaded, curried and polymorphic methods
Overloaded, curried and polymorphic methods can be mocked by specifying either argument types or type parameters. For example:
trait Foo { def overloaded(x: Int): String def overloaded(x: String): String def overloaded[T](x: T): String def curried(x: Int)(y: Double): String def polymorphic[T](x: List[T]): String }
val m = mock[Foo] (m.overloaded(_: Int)).expects(10) (m.overloaded(_: String)).expects("foo") (m.overloaded[Double] _).expects(1.23) (m.curried(_: Int)(_: Double)).expects(10, 1.23) (m.polymorphic(_: List[Int])).expects(List(1, 2, 3)) (m.polymorphic[String] _).expects("foo")
Exceptions
Instead of a return value, mocks and stubs can be instructed to throw:
m expects ("this", "that") throws new RuntimeException("what's that?")
Call count
By default, mocks and stubs expect exactly one call. Alternative constraints
can be set with repeat:
m1.expects(42).returns(42).repeat(3 to 7) m2 expects (3) repeat 10
There are various aliases for common expectations and styles:
m1.expects("this", "that").once m2.expects().returns("foo").noMoreThanTwice m3.expects(42).repeated(3).times
For a full list, see org.scalamock.handlers.CallHandler.
Ordering
By default, expectations can be satisfied in any order. For example:
m expects (1) m expects (2) m(2) m(1)
A specific sequence can be enforced with inSequence:
inSequence {
m expects (1)
m expects (2)
}
m(2) // throws ExpectationException
m(1)Multiple sequences can be specified. As long as the calls within each sequence happen in the correct order, calls within different sequences can be interleaved. For example:
inSequence {
m expects (1)
m expects (2)
}
inSequence {
m expects (3)
m expects (4)
}
m(3)
m(1)
m(2)
m(4)To specify that there is no constraint on ordering, use inAnyOrder (there is an implicit
inAnyOrder at the top level). Calls to inSequence and inAnyOrder can be arbitrarily
nested. For example:
(m.a _).expects()
inSequence {
(m.b _).expects()
inAnyOrder {
(m.c _).expects()
inSequence {
(m.d _).expects()
(m.e _).expects()
}
(m.f _).expects()
}
(m.g _).expects()
}Threads
ScalaMock will work with tests that are run in parallel (Specs2 runs tests in parallel by
default, and ScalaTest does so with ParallelTestExecution).
You can call mocks from other threads within tests, but any such calls must be complete before the test completes - it's an error to call a mock afterwards.
Type Members
-
trait
AbstractMockFactoryBase extends Mock with MockFunctions with Matchers
ScalaMock public interface
- trait MockFactoryBase extends AbstractMockFactoryBase with MockContext
ScalaMock
This is the documentation for ScalaMock
For an overview, see org.scalamock.