java - Mockito UnfinishedStubbingException

Question

I am new to Mockito, I have tried looking into this Exception but I haven′t found a concrete answer. It happens in my code when I use two mocks together, meaning that I give through the constructor of a mock, another mock. Like so:

...
OperationNode child = getNode(Operation.ADD);
child.insertNode(getConstantNode(getIntegerValue(2));
...

 private ConstantNode getConstantNode(NumericalValue value){
    ConstantNode node = Mockito.mock(ConstantNode.class);
    Mockito.when(node.evaluate()).thenReturn(value);
    Mockito.when(node.toString()).thenReturn(value.toString());
    return node;
}

private IntegerValue getIntegerValue(int number) {
   IntegerValue integerValue = Mockito.mock(IntegerValue.class);
   Mockito.when(integerValue.getValue()).thenReturn(number);
   Mockito.when(integerValue.toString()).thenReturn(Integer.toString(number));
   return integerValue;
}

In one of the forums I read about not sending a mock through a constructor of another mock, since Mockito might get confused with the mock calls, so I tried the following:

NumericalValue value = getIntegerValue(2);
child.insertNode(getConstantNode(value));

But to no avail. I make sure that only the methods toString() and getValue() are called, because those are the only methods the class has. I don′t understand what′s going on.

I have also tried using the mocks separately, to see if I have done something wrong:

child.insertNode(new ConstantNode(getIntegerValue(2)));

That works perfectly.

child.insertNode(getConstantNode(new IntegerValue(2)));

That works fine too.

Answer 1

From what I read on "Issue 53" of mockito (https://code.google.com/p/mockito/issues/detail?id=53) , my code was experiencing a problem due to the validation framework involved in Mockito. Precisely the following code was causing the exception per se.

private ConstantNode getConstantNode(NumericalValue value){
    ConstantNode node = Mockito.mock(ConstantNode.class);
    Mockito.when(node.evaluate()).thenReturn(value);
    Mockito.when(node.toString()).thenReturn(value.toString());
    return node;
}

If you remember from my code, the parameter value is ALSO A MOCK, so that when value.toString() is called on the thenReturn(), I believe (and someone please correct me if I am wrong) that the validation framework is triggered and makes sure that every "when" has had its thenReturn() called/validated/etc. So that if this happenes, the Mockito.when(node.toString()).thenReturn(value.toString() will not be validated because it hasn′t returned from the valute.toString(), which started the whole "validate everything" chain.

How I fixed it:

private ConstantNode getConstantNode(NumericalValue value){
    ConstantNode node = Mockito.mock(ConstantNode.class);
    Mockito.when(node.evaluate()).thenReturn(value);

    String numberToString = value.toString();

    Mockito.when(node.toString()).thenReturn(numberToString);
    return node;
}

This way, it can be validated. I find this a complete code smell because I will literally have to leave a comment that explains why I am using a seemingly useless intermediate variable in the code.

Thanks for the help.