Mockito - 0 Matchers Expected, 1 Recorded (InvalidUseOfMatchersException)

Question

I'm trying to mock up some mongo classes so that I don't need a connection (fairly standard stuff) but the following code gives me problems:

when(dbCollection.find(isA(DBObject.class))).thenReturn(dbCursor);

Running this get's me:

org.mockito.exceptions.misusing.InvalidUseOfMatchersException:
Invalid use of argument matchers!
0 matchers expected, 1 recorded:
at ...GridFileManagerTest.beforeClass(GridFileManagerTest.java:67)

This exception may occur if matchers are combined with raw values:
//incorrect: someMethod(anyObject(), "raw String");

When using matchers, all arguments have to be provided by matchers.
For example:
//correct:
someMethod(anyObject(), eq("String by matcher"));

For more info see javadoc for Matchers class.

If I were to do this though:

when(dbCollection.find(mock(DBObject.class))).thenReturn(dbCursor);

it no longer has that problem. This doesn't seem to accomplish what I want though - I want to return the value when the method is called with an object of type DBObject.

Thoughts?

Answer 1

I think your results are compatible with the result that would happen if dbCollection is not a Mockito-mock (or your method is static or final). That would mean that a matcher is being used where none can be used; hence the "0 matchers expected, 1 recorded".

Answer 2

This same issue can be reproduced in Scala if you have default arguments. It may look like you're providing any() for every argument, but you should verify that the method definition doesn't have any default parameters which might be messing things up.