Mockito - NullpointerException when stubbing Method

Question

So I started writing tests for our Java-Spring-project.

What I use is JUnit and Mockito. It\'s said, that when I use the when()...thenReturn() option I can mock ser

Answer 1

Another common gotcha is that the method signature is accidentally declared as 'final'.

This one catches out a lot of people who work on codebases which are subjected to Checkstyle and have internalised the need to mark members as final.

i.e. in the OP's example:

object.method()

Make sure that method() is not declared as final:

public final Object method() {
}

Mockito cannot mock a final method and this will come up as a wrapped NPE:

Suppressed: org.mockito.exceptions.misusing.InvalidUseOfMatchersException:

Buried deep in the error message is the following:

Also, this error might show up because you use argument matchers with methods that cannot be mocked.
Following methods *cannot* be stubbed/verified: final/private/equals()/hashCode().
Mocking methods declared on non-public parent classes is not supported.