How to mock a single method in java

Question

Is it possible to Mock a single method of a Java class?

For example:

class A {
    long method1();
    String method2();
    int method3();
}


// in         


        

Answer 1

Use the spy() method from Mockito, and mock your method like this:

import static org.mockito.Mockito.*;

...

A a = spy(new A());
when(a.method1()).thenReturn(10L);

Answer 2

You could simply create a subclass of A that overrides method1().

Answer 3

Assuming you are using jmockit:

public void testCase(@Mocked("methodToBeMocked") final ClassBoBeMocked mockedInstance) {
           new Expectations() {{
                   mockedInstance.methodToBeMocked(someParameter); returns(whateverYouLikeItToReturn);
           }}

   mockedInstance.callSomemethod();
}

Answer 4

Use Mockito's spy mechanism:

A a = new A();
A aSpy = Mockito.spy(a);
Mockito.when(aSpy.method1()).thenReturn(5l);

The use of a spy calls the default behavior of the wrapped object for any method that is not stubbed.

Mockito.spy()/@Spy