User Guide - Advanced topics

Advanced topics

Mocking overloaded, curried and polymorphic methods

Overloaded, curried and polymorphic methods can be mocked by specifying either argument types or type parameters.

Example 1 - Overloaded methods

trait Foo {
  def overloaded(x: Int): String
  def overloaded(x: String): String
  def overloaded[T](x: T): String

val fooMock = mock[Foo]

(fooMock.overloaded(_: Int)).expects(10)
(fooMock.overloaded(_: String)).expects("foo")
(fooMock.overloaded[Double] _).expects(1.23)

You may also prefer to use slightly different syntax:

(fooMock.overloaded _: Int => String).expects(10)  // or
(fooMock.overloaded _: Int => String) expects (10) // or
(fooMock.overloaded(_: Int)) expects (10)

Example 2 - Polymorphic methods

trait Foo {
  def polymorphic[T](x: List[T]): String

val fooMock = mock[Foo]

(fooMock.polymorphic(_: List[Int])).expects(List(1, 2, 3))            // or
(fooMock.polymorphic[Int] _).expects(List(1, 2, 3))                   // or
(fooMock.polymorphic _ : List[Int] => String).expects(List(1, 2, 3))

Example 3 - Curried methods

trait Foo {
  def curried(x: Int)(y: Double): String

val fooMock = mock[Foo]

(fooMock.curried(_: Int)(_: Double)).expects(10, 1.23)

Example 4 - Methods with implicit parameters

This case is very similar to curried methods - all you need to do is to help scala compiler know that memcachedMock.get _ should be converted to MockFunction2. For example:

class Codec()

trait Memcached {
  def get(key: String)(implicit codec: Codec): Option[Int]

val memcachedMock = mock[Memcached]

implicit val codec = new Codec
(memcachedMock.get(_ : String)(_ : Codec)).expects("some_key", *).returning(Some(123))

Example 5 - Repeated parameters

Repeated parameters are represented as a Seq. For example, given:

trait Foo {
  def takesRepeatedParameter(x: Int, ys: String*)

you can set an expectation with:

(fooMock.takesRepeatedParameter _).expects(42, Seq("red", "green", "blue"))

Returning values (onCall)

By default mocks and stubs return null. You can return predefined value using returning() method (or returns() in case of stubs). When returned value depends on function arguments, you can return the computed value (or throw a computed exception) with onCall().

trait Foo {
    def increment(a: Int): Int

val fooMock = mock[Foo]

(fooMock.increment _) expects(12) returning(13)
fooMock.increment(12) shouldBe 13 

(fooMock.increment _) expects(*) onCall { arg: Int => arg + 1}
fooMock.increment(100) shouldBe 101

(fooMock.increment _) expects(*) onCall { arg: Int => throw new RuntimeException("message") }
intercept[RuntimeException] { fooMock.increment(0) }
val mockIncrement = mockFunction[Int, Int]
mockIncrement expects (*) onCall { arg: Int => arg + 1 }
mockIncrement(10) shouldBe  11 

Call count

By default, mocks and stubs expect exactly one call. Alternative constraints can be set with repeat():

mockedFunction.expects(42).returns(42).repeat(3 to 7)
mockedFunction expects (3) repeat 10

There are various aliases for common expectations and styles:

val mockedFunction1 = mockFunction[Int, String]
val mockedFunction2 = mockFunction[Int, String]
val mockedFunction3 = mockFunction[Int, String]
val mockedFunction4 = mockFunction[Int, String]
val mockedFunction5 = mockFunction[Int, String]

mockedFunction4.expects(4).returning("foo").repeat(1 to 2)


//mockedFunction2(2) - not called




//mockedFunction6(6) - not called

For a full list, see org.scalamock.CallHandler.


Instead of a return value, mocks and stubs can be instructed to throw. This can be achieved either by throwing exception in onCall handler or by using throws method.

Example 1 - throws method

trait Foo {
  def increment(a: Int): Int

val fooMock = mock[Foo]

(fooMock.increment _) expects (5) throws new RuntimeException("message")

intercept[RuntimeException] { fooMock.increment(5) }

Example 2 - throwing from onCall handler

(fooMock.increment _) expects(*) onCall { arg: Int => 
  if (arg == 0) 
      throw new RuntimeException("message") 
      arg + 1

intercept[RuntimeException] { fooMock.increment(0) }

Partial Functions

Example 1

val m = mockFunction[Int, String]
val mp = new PartialFunction[Int, String] {
  def isDefinedAt(x: Int) = true
  def apply(v1: Int) = m(v1)

m expects 42 returning "foo" once()

mp(42) shouldBe "foo"

Raw types

Example 1

Try this solution if you get this error:

error: could not find implicit value for evidence parameter of type org.scalamock.Defaultable[SomeType]

e.g. like below for Enumeration and Map

public interface RawTypeInterface {
    java.util.Enumeration foo();
    java.util.Map bar();
"mocking a java method with raw type" should "work" in {
  implicit val d = new Defaultable[java.util.Enumeration[_]] {
    override val default = null
  implicit val d2 = new Defaultable[java.util.Map[_, _]] {
    override val default = null
  val mockedRaw = mock[RawTypeInterface]

Log Calls

Example 1

inAnyOrderWithLogging { // or inSequenceWithLogging _ expects() returning 42 anyNumberOfTimes()

This will print all invocations of call handlers and verifiers, with the corresponding calls.