ScalaMock

Native Scala mocking.

Official website: scalamock.org

Examples

Expectations-First Style

test("drawline interaction with turtle") {
  // Create mock Turtle object
  val m = mock[Turtle]
  
  // Set expectations
  (m.setPosition _).expects(10.0, 10.0)
  (m.forward _).expects(5.0)
  (m.getPosition _).expects().returning(15.0, 10.0)

  // Exercise System Under Test
  drawLine(m, (10.0, 10.0), (15.0, 10.0))
}

Record-then-Verify (Mockito) Style

test("drawline interaction with turtle") {
  // Create stub Turtle
  val m = stub[Turtle]
  
  // Setup return values
  (m.getPosition _).when().returns(15.0, 10.0)

  // Exercise System Under Test
  drawLine(m, (10.0, 10.0), (15.0, 10.0))

  // Verify expectations met
  (m.setPosition _).verify(10.0, 10.0)
  (m.forward _).verify(5.0)
}

A more complete example is on our Quickstart page.

Features

• Fully typesafe
• Full support for Scala features such as:
  • Polymorphic (type parameterised) methods
  • Operators (methods with symbolic names)
  • Overloaded methods
  • Type constraints
• ScalaTest and Specs2 integration
• Mock and Stub support
• Macro Mocks and JVM Proxy Mocks
• Scala.js support
• built for Scala 2.12, 2.13, 3
• Scala 2.10 support was included up to ScalaMock 4.2.0
• Scala 2.11 support was included up to ScalaMock 5.2.0

Using ScalaMock

Artefacts are published to Maven Central and Sonatype OSS.

For ScalaTest, to use ScalaMock in your Tests, add the following to your build.sbt:

libraryDependencies += Seq("org.scalamock" %% "scalamock" % "5.2.0" % Test,
    "org.scalatest" %% "scalatest" % "3.2.0" % Test)

Scala 3 Migration Notes

1. Type should be specified for methods with by-name parameters

trait TestTrait:
  def byNameParam(x: => Int): String

val t = mock[TestTrait]

// this one no longer compiles
(t.byNameParam _).expects(*).returns("")

// this one should be used instead
(t.byNameParam(_: Int)).expects(*).returns("")

• Not initialized vars are not supported anymore, use scala.compiletime.uninitialized instead
• Vars are not mockable anymore

trait X:
  var y: Int  // No longer compiles
  
  var y: Int = scala.compile.uninitialized // Should be used instead

Mocking of non-abstract java classes is not available without workaround

public class JavaClass {
    public int simpleMethod(String b) { return 4; }
}

val m = mock[JavaClass] // No longer compiles

class JavaClassExtended extends JavaClass

val mm = mock[JavaClassExtended] // should be used instead

Documentation

For usage in Maven or Gradle, integration with Specs2, and more example examples see the User Guide

Acknowledgements

YourKit is kindly supporting open source projects with its full-featured Java Profiler. YourKit, LLC is the creator of innovative and intelligent tools for profiling Java and .NET applications. Take a look at YourKit's leading software products: YourKit Java Profiler and YourKit .NET Profiler.

Many thanks to Jetbrains for providing us with an OSS licence for their fine development tools such as IntelliJ IDEA.

Also, thanks to https://github.com/fthomas/scala-steward for helping to keep our dependencies updated automatically.