Making a mocked method return an argument that was passed to it

Consider a method signature like:

public String myFunction(String abc);

Can Mockito help return the same string that the method received?

Since Mockito 1.9.5+ and Java 8+

You can use a lambda expression, like:

when(myMock.myFunction(anyString())).thenAnswer(i -> i.getArguments()[0]);

Where i is an instance of InvocationOnMock.

For older versions

You can create an Answer in Mockito. Let's assume, we have an interface named MyInterface with a method myFunction.
public interface MyInterface {
public String myFunction(String abc);
}


Here is the test method with a Mockito answer:
public void testMyFunction() throws Exception {
MyInterface mock = mock(MyInterface.class);
when(mock.myFunction(anyString())).thenAnswer(new Answer() {
@Override
public String answer(InvocationOnMock invocation) throws Throwable {
Object[] args = invocation.getArguments();
return (String) args[0];
}
});

assertEquals("someString",mock.myFunction("someString"));
assertEquals("anotherString",mock.myFunction("anotherString"));
}


Stack Overflow Q#2684630, score: 1447