Monday, May 23, 2016

Continuous iOS Code Coverage With Jenkins and Slather

Matej Bukovinski:

Before Xcode 7, we already had code coverage reporting set up with Jenkins. We generated coverage data in the gcov format and used LCOV together with a custom script to integrate the coverage data into Jenkins. It all worked pretty well. However, with the introduction of Xcode 7, Apple dropped support for the legacy gcc coverage file format and introduced a format of its own: profdata. Of course this broke our setup as soon as we migrated our CI servers to Xcode 7. As framework developers, we always have to be early adopters of the latest iOS versions, so we can make sure our code is ready before our clients make the switch. Unfortunately, this means in some cases we need to make a few compromises. In this particular circumstance, it meant dropping code coverage because there were simply no convenient tools around to get the data into Jenkins. Xcode ships with llvm-cov, a command line tool that can convert the coverage data into a more human readable format. However, there is still quite a bit of work needed to get it into a format that Jenkins could handle.


After running llvm-cov Slather parses the output data, processes it a bit and then outputs it into one of the supported formats. In our case an XML file suitable for Cobertura.

To get all that running on Jenkins, we simply added a call to rake coverage_ios right after we run our test suite. We have some extra logic to prevent coverage from running in certain configurations or if the tests fail but that is essentially all that is needed to generate the XML coverage data. After adding the call, we just need to install the Cobertura plugin and configure it so it can find the generated XML.

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