How does Mockito handle overlapping matchers with multiple arguments in the thenReturn block

Question

I\'ve got a block of test code that is attempting to, in the generic case return two values on subsequent calls, but in specific cases only return the value associated with that

Answer 1

One way to workaround this problem could be to use a regular expression to avoid overlapping as next:

when(mockObject.method(eq("expectedInput1"))).thenReturn(string1);
when(mockObject.method(eq("expectedInput2"))).thenReturn(string2);
// Match with any input string that doesn't contain expectedInput1 neither expectedInput2
when(mockObject.method(matches("((?!expectedInput1|expectedInput2).)*")))
    .thenReturn(string1, string2);

Example:

System.out.println("expectedInput1=" + mockObject.method("expectedInput1"));
System.out.println("expectedInput2=" + mockObject.method("expectedInput2"));
System.out.println("foo=" + mockObject.method("foo"));
System.out.println("bar=" + mockObject.method("bar"));
System.out.println("bar=" + mockObject.method("bar"));

Output:

expectedInput1=string1
expectedInput2=string2
foo=string1
bar=string2
bar=string2

---

Another way could be to implement your ArgumentMatcher still to avoid overlapping:

when(mockObject.method(eq("expectedInput1"))).thenReturn(string1);
when(mockObject.method(eq("expectedInput2"))).thenReturn(string2);
when(
    mockObject.method(
        argThat(
            new ArgumentMatcher(){
                @Override
                public boolean matches(final Object argument) {
                    return !"expectedInput1".equals(argument) 
                        && !"expectedInput2".equals(argument);
                }
            }
        )
    )
).thenReturn(string1, string2);

---

Another way could be to implement your Answer with something like this:

when(mockObject.method(anyString())).thenAnswer(
    new Answer() {
        Iterator it = Arrays.asList(string1, string2).iterator();
        String result;
        @Override
        public String answer(final InvocationOnMock invocation) throws Throwable {
            String argument = (String) invocation.getArguments()[0];
            switch (argument) {
                case "expectedInput1" :
                    return string1;
                case "expectedInput2" :
                    return string2;
                default:
                    if (it.hasNext()) {
                        result = it.next();
                    }
                    return result;
            }
        }
    }
);