Use mockito to mock method with Object parameter

Question

I have a method :

public class Sender{ public Object send(Object param){ Object x; ..... return (x); } }

I want to write a unit test for this method using Mockito such that the return type value is based on the class type of the paramter. So I did this:

when(sender.send(Matchers.any(A.class))).thenReturn(value1); when(sender.send(Matchers.any(B.class))).thenReturn(value2);

but the return value irrespective of the parameter class type is always value 2. How do it get this to return value 1 for class A type argument and value 2 for class B type argument.

noscreenname · Accepted Answer · 2016-07-22 16:08:07Z

when(sender.send(Matchers.any(A.class))).thenReturn(value1);

Mockito will try to mock a method with signature send(A param), not send(Object param).

What you need is to return a different value base on the class of you parameter. You need to use Answers for this.

Mockito.doAnswer(invocationOnMock -> { if(invocationOnMock.getArguments()[0].getClass() instanceof A) { return value1; } if(invocationOnMock.getArguments()[0].getClass() instanceof B) { return value2; } else { throw new IllegalArgumentException("unexpected type"); } }).when(mock).send(Mockito.anyObject());

@noscreenname Ahh! Can you convert this to not using the lambda expression please? I understand the intent but unable to replicate it.
@Sherlock123 I could, but so could you if you look up Mockito.doAnswer() documentation ;)

Christopher Schneider · Accepted Answer · 2016-07-22 16:00:57Z

A couple options:

Don't use any. Use the instance of A or B you're using in the test.
Use an Answer object, which would allow you to specify what to return.

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