Myth: Acceptance tests should be functional (end to end) tests

Did you hear the one about the gynaecologist who decorated his hallway through the letterbox?

Given sufficient tools, enough effort, and considerable skill it might be possible to paper your hall from outside your front door. It’d be a damn site easier to do it close-up, though.

The purpose of XP Acceptance Tests is to communicate how the system works. Functional tests typically need lots of supporting set-up data and can be easily broken by changes to unrelated parts of the system. Get up close: plug the test into the code that expresses the rule under test. If you can’t find an isolated bit of code that expresses the rule, it may be time to reconsider your design. If your test is covering many different concepts, it may be time to reconsider the clarity of your test.

In his Art of Agile book, Jim Shore underlines this point by calling acceptance-style tests Customer Unit Tests.

Wednesday, August 22, 2007 | Permalink | 0 Comments