Mockito modify method behavior

Question

I have the following interface:

public interface Test{
    public void block(String modifier);
    public boolean blocked(String modifier);
}

So I wanted to mock this interface as follows:

Test m = Mockito.mock(Test.class);
when(m.blocked(Mockito.any()).thenReturn(true);
//I want to mock m.block()

Buty I want to mock Test::block(String) the way so when it is called on some String someString it changes the behavior so that m.blocked(someString) will return false.

Is it possible to do so in Mockito?

You could have a boolean field, and rather then use thenReturn, use thenAnswer and create a logic using this field — Paedolos, Nov 22 '17 at 22:46
https://stackoverflow.com/questions/26067096/how-to-write-a-matcher-that-is-not-equal-to-something — ronhash, Nov 22 '17 at 22:48

score 4 · Accepted Answer · answered Nov 22 '17 at 23:02

You can use thenAnswer and doAnswer to execute arbitrary code when a method is called. For example, you could use a Set to keep track of the strings that have already been blocked:

Set<Object> blocked = new HashSet<>();
Test m = mock(Test.class);
doAnswer(invocation -> blocked.add(invocation.getArguments()[0]))
    .when(m).block(any());
when(m.blocked(any()))
    .thenAnswer(invocation -> !blocked.contains(invocation.getArguments()[0]));

score 1 · Answer 2 · answered Nov 22 '17 at 22:53

Here's a sample, assuming you have a boolean field that starts as true --

when(m.blocked(Mockito.any()).thenAnswer(invocation -> this.mockValue);
when(m.block(Mockito.eq("Some String")).thenAnswer(invocation -> {
    this.mockValue = false;
    return null;
});

Hopefully I didn't get the syntax wrong :-)

Mockito modify method behavior

2 Answers2