Unfinished stubbing detected here: -> at org.apache.pulsar.broker.admin.PersistentTopicsTest.setup(PersistentTopicsTest.java:179) E.g. thenReturn() may be missing. Examples of correct stubbing: when(mock.isOk()).thenReturn(true); when(mock.isOk()).thenThrow(exception); doThrow(exception).when(mock).someVoidMethod(); Hints: 1. missing thenReturn() 2. you are trying to stub a final method, which is not supported 3. you are stubbing the behaviour of another mock inside before 'thenReturn' instruction is completed