Rob Smyth

Monday, 29 October 2007

Using Continous Integration To Raise Code Coverage

I'm constantly amazed by what I learn working in a team, somebody is always coming up with something real useful. This last couple of weeks it was a simple extension to our continuous integration (CI) build box that measures the code coverage of the build and compares it to the highest recorded code coverage. If it is less the build fails, yep fails. If it is higher then the highest recorded is automatically updated with the builds coverage. Being a CI environment any build box failure must be fixed immediately. As a result the code coverage can only go up.

So far this has been amazing successful, but then our team does practice TDD (well mostly).

The implications are that if you are committing new code you are responsible to ensure that your code is covered by unit tests (code coverage is only calculated from unit tests). This is something of a subtle move in responsibility as before it was acceptable to 'think' that the code was covered now we must 'ensure' that it is covered or the build will break within minutes of the check-in.

For this to work developer boxes were set-up so that each developer can run their own code coverage (before check-in) and view the added code for coverage (using NCoverExplorer) quickly and easily. I think that things being easy is really essential.

Like many things I've blogged about I'm really recording great ideas from the team or others. This is no exception (credit here to Nigel Thorne ... a wickedly good idea Nigel).

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