Simplifying Mock Object Testing

Facilitated by Tom Adams

Overview

• Tom walked through setting up a unit test using mocks (using JMock 1).
• He demonstrated how hard it can be to read even the most simple interactions due to the amount of scaffolding required
• The group contributed to DRYing up the scaffolding
• A superclass for mock object testing was created to house the simplified scaffolding
• The unit tests became so simple that they appeared to simply be duplicating production code

Tools people mentioned

• JMock 1
• JMock2 wraps “mock” and “controller” in one
  • Side effect: need to have some way of explicitly moving from expectation-setting mode and replay mode. JMock2 is closer to the EasyMock style of explicit value seeding and method replay.
• EasyMock
• RMock
• PicoUnit

Summary / comments

• DRY up your mock setup
• Create methods that express intent, e.g. Stack stack = makeMock(Stack.class);
• Put these methods into an abstract testing class (e.g. MockObjecTestCase) for reuse
• Use annotations to further reduce scaffolding and make roles more explicit (auto mocking)
• At some point, the behavioural tests mirror production code and perhaps for non-state-based testing at some point the value is reduced