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 some other class class B {     void someMethod(A a) {        // how would I mock A.method1(...) such that a.method1() returns a value of my        // choosing;        // whilst leaving a.method2() and a.method3() untouched.     } } 

Answer 1

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

Answer 2

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);