neworld/mockito-kotlin

Using Mockito with Kotlin

Mockito-Kotlin

A small library that provides helper functions to work with Mockito in Kotlin.

Install

Mockito-Kotlin is available on JCenter. For Gradle users, add the following to your build.gradle:

repositories {
    jcenter()
}
dependencies {
    testCompile "com.nhaarman:mockito-kotlin:x.x.x"
}

Examples

Creating mock instances

Due to Kotlin's reified type parameters, if the type can be inferred, you don't have to specify it explicitly:

Java:

MyClass c = mock(Myclass.class);
c.doSomething(mock(MyOtherClass.class));

Kotlin:

val c : MyClass = mock()
c.doSomething(mock())

If the type can't be inferred, you can pass it like so:

val d = mock<MyClass>()

Expecting any value

Mockito's any(Class<T>) often returns null for non-primitive classes. In Kotlin, this can be a problem due to its null-safety feature. This library creates non-null instances when necessary. Again, if the type can be inferred, you don't have to specify it explicitely:

Java:

verify(myClass).doSomething(any(String.class));

Kotlin:

verify(myClass).doSomething(any()); // Non-nullable parameter type is inferred

For generic arrays, use the anyArray() method:

verify(myClass).setItems(anyArray())

Argument Matchers

Using higher-order functions, you can write very clear expectations about expected values. For example:

Kotlin:

verify(myClass).setItems(argThat{ size == 2 })

Convenience functions

Most of Mockito's static functions are available as top-level functions. That means, IDE's like IntelliJ can easily import and autocomplete them, saving you the hassle of manually importing them.