How to mock a final class with mockito

Question

I have a final class, something like this:

public final class RainOnTrees{

   public void startRain(){

        // some code here
   }
}

I

Answer 1

This can be done if you are using Mockito2, with the new incubating feature which supports mocking of final classes & methods.

Key points to note:
1. Create a simple file with the name “org.mockito.plugins.MockMaker” and place it in a folder named “mockito-extensions”. This folder should be made available on the classpath.
2. The content of the file created above should be a single line as given below:
mock-maker-inline

The above two steps are required in order to activate the mockito extension mechanism and use this opt-in feature.

Sample classes are as follows:-

FinalClass.java

public final class FinalClass {

public final String hello(){
    System.out.println("Final class says Hello!!!");
    return "0";
}

}

Foo.java

public class Foo {

public String executeFinal(FinalClass finalClass){
    return finalClass.hello();
}

}

FooTest.java

public class FooTest {

@Test
public void testFinalClass(){
    // Instantiate the class under test.
    Foo foo = new Foo();

    // Instantiate the external dependency
    FinalClass realFinalClass = new FinalClass();

    // Create mock object for the final class. 
    FinalClass mockedFinalClass = mock(FinalClass.class);

    // Provide stub for mocked object.
    when(mockedFinalClass.hello()).thenReturn("1");

    // assert
    assertEquals("0", foo.executeFinal(realFinalClass));
    assertEquals("1", foo.executeFinal(mockedFinalClass));

}

}

Hope it helps.

Complete article present here mocking-the-unmockable.