Dynamic chaining "thenReturn" in mockito

java unit-testing mockito chaining method-chaining
gjain picture gjain · Jul 29, 2014 · Viewed 8.7k times · Source

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

gjain picture gjain · Jul 29, 2014

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

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