PHPUnit is one of the most widely used unit testing tools for PHP applications. It comes packed with features, some that are commonly used and some not so much. In a new post to his blog today Volker Dusch looks at one specific feature - the "@covers" annotation you can use in your tests' comments to specify which functionality you're actually testing.

One of the goals of your test suite and the coverage report is to make you trust in your code base and to remove the fear of changing something that needs to be changed. [...] You shouldn't think "Well yes that a 100% but a lot of that just comes from that big integration test and I don't know if the class is really tested!". [...] Thankfully PHPUnit offers a way to drastically increase your confidence in what you actually have tested.

Using the "@covers" annotation on your test method docblocks gives you one more level of confidence in what's being tested and can help make for clearer updating down the road. He also mentions using them to provide extra insight into protected methods in your code and where the test coverage for them really lies.