Testing multi-threaded code can become arbitrarily complex. However, in most cases, it doesn’t need to. The following formula should cover the majority of cases:
- Unit test the “work” performed by each thread in isolation. (If you absolutely need to, write some integration tests.)
- Unit test the multi-threaded code, focusing on the concurrent parts, i.e., verify that the correct sequence of operations is happening using mocks or spies.
- If the above takes too long. Move the test out of the unit test suite into a suite that runs slower tests.
- Alternatively, write a slower test that aims for eventual consistency, i.e., lets the threads do whatever they want and they verifies the expected end state.
Book References
Read more about this topic in Developer Testing: Building Quality into Software:
Read more about this topic in Developer Testing: Building Quality into Software:
- Chapter 12: Test Doubles, pages 164-171
