Dynamic chaining "thenReturn" in mockito

Question

I have a Tuple mock class, whose getString(0) and getString(1) methods are expected to be called n times. Instead of writing something like,

when(tuple.getString(0)).thenReturn(logEntries[0]).thenReturn(logEntries[1])...thenReturn(logEntries[n - 1])

manually, I tried the following:

OngoingStubbing stubbingGetStringZero = when(tuple.getString(0)).thenReturn(serviceRequestKey);
OngoingStubbing stubbingGetStringOne = when(tuple.getString(1)).thenReturn(logEntries[0]);
for (int i = 1; i < n; i++) {
    stubbingGetStringZero = stubbingGetStringZero.thenReturn(serviceRequestKey);
    stubbingGetStringOne = stubbingGetStringOne.thenReturn(logEntries[i]);
}

The expected result is that all calls to tuple.getString(0) should return the String serviceRequestKey and each call to tuple.getString(1) should return a different String logEntries[i] ie. ith invocation of tuple.getString(1) returns ith element of logEntries array.

However, due to some odd reason, things are getting mixed up, and second invocation to tuple.getString(1) returns the String serviceRequestKey instead of logEntries[1]. What am I missing here?

Answer 1

Well, the right way to do this would be:

import org.mockito.AdditionalAnswers;

String[] logEntry = // Some initialization code
List<String> logEntryList = Arrays.asList(logEntry);
when(tuple.getString(1)).thenAnswer(AdditionalAnswers.returnsElementsOf(logEntryList));

On each invocation, successive elements of logEntry array are returned. Thus, ith invocation of tuple.getString(1) returns ith element of logEntry array.

P.S: The example in documentation of returnsElementsOf (as of this writing) is not updated (it still uses ReturnsElementsOf example): http://docs.mockito.googlecode.com/hg/1.9.5/org/mockito/AdditionalAnswers.html#returnsElementsOf(java.util.Collection)it

Answer 2

If I understood well, you want your mock to return different results depending on the invocation (meaning result1 when invoked for the first time, result2 when invoked for the second time etc)- this can be accomplished with such thing

Mockito.when(tuple.getString(0)).thenReturn(serviceRequestKey,logEntries[0],logEntries[1])

With this you will get serviceRequestKey on first invocation, logEntries[0] on second etc...

If you want something more sophisticated, like change the return depending on the param in the method use thenAnswer() as shown here