Differences from Mock

If you’ve previously used the Mock package, you may be wondering how dobles is different and why you might want to use it. There are a few main differences:

• Mock follows what it describes as the “action –> assertion” pattern, meaning that you make calls to test dobles and then make assertions afterwards about how they are used. dobles takes the reverse approach: you declare explicitly how your test dobles should behave, and any expectations you’ve made will be verified automatically at the end of the test.

• Mock has one primary class, also called Mock, which can serve the purpose of different types of test dobles depending on how it’s used. dobles uses explicit terminology to help your tests better convey their intent. In particulary, there is a clear distinction between a stub and a mock, with separate syntax for each.

• dobles ensures that all test dobles adhere to the interface of the real objects they double. This is akin to Mock’s “spec” feature, but is not optional. This prevents drift between test double usage and real implementation. Without this feature, it’s very easy to have a passing test but broken behavior in production.

• dobles has a fluid interface, using method chains to build up a specification about how a test double should be used which matches closely with how you might describe it in words.