org.mockito.exceptions.misusing.MissingMethodInvocationException: when() requires an argument which has to be 'a method call on a mock'.
Also, this error might show up because:
1. you stub either of: final/private/equals()/hashCode() methods.
Those methods *cannot* be stubbed/verified.
Mocking methods declared on non-public parent classes is not supported.
2. inside when() you don't call method on mock but on some other object.