Mockito Stubbing callbacks - callback

Question

I am new to Mockito. I am using mockito 1.9.5. and junit 4 that comes with eclipse kepler.
When I ran this test in my junit below.
<pre><code>
#SuppressWarnings("rawtypes")
#Test
public void stubbingCallbacks(){
when(mockedList.add(anyString())).thenAnswer(new Answer() {
public Object answer(InvocationOnMock invocation) {
Object[] args = invocation.getArguments();
//Object mock = invocation.getMock();
return "called with arguments: " + args;
}
});
System.out.println(mockedList.add("a"));
}
</code></pre>
Then it throws me this exception
java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Boolean
at $java.util.LinkedList$$EnhancerByMockitoWithCGLIB$$2744633c.add()
at com.mock.Verifying.stubbingCallbacks(Verifying.java:185)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Does anyone know why is it throwing ClassCastException? And
How do I solve this problem?
Thank you so much for your help
Sura

Answer 1

Yes of course : List.add(item) returns a boolean and your answer returns a String.

Answer 2

It's not possible to violate the return type of the method you are mocking. The return value of mockedList.add() is boolean so your mock should also be boolean other than "called with arguments: " + args