In a new post to his site Matthias Noback has a post showing you how to, when using the Behat functional testing framework, to create local and remote code coverage metrics.
PHPUnit has built-in several options for generating code coverage data and reports. Behat doesn't. As Konstantin Kudryashov (@everzet) points out in an issue asking for code coverage options in Behat: "Code coverage is controversial idea and code coverage for StoryBDD framework is just nonsense. If you're doing code testing with StoryBDD - you're doing it wrong."
He starts off by talking about code coverage and why you might want it for the tests created through Behat. Code coverage metrics are usually associated with unit tests but having those numbers for the functional tests can be helpful too. He then covers the two pieces of the puzzle needed to gather the coverage numbers: an extension for the local coverage and one for the remote coverage. He shows how to get both of these installed, configured and used in the code to gather the results. Finally he shows how to use the phpcov tool to merge these results with the PHPUnit results to get a better overall view of coverage numbers.