Visual Studio Code Coverage reports with MSBuild

Recently I had a project where I was using Microsoft Visual Studio 2008 Team System for development and CruiseControl.NET for doing continuous integration. I usually care about code coverage when running unit tests, so I decided to integrate the code profiling tool included in Visual Studio Team System as part of my build process, in order to produce a code coverage report with each build.

I figured that wouldn’t be too hard, all I had to do in my build script was to invoke Visual Studio’s test runner’s executable (usually found in C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE\MSTest.exe) passing an option to enable code coverage profiling, and grab the output in a file that CruiseControl.NET would later use to produce the build report.

However, I quickly found out that Visual Studio’s test runner produces code coverage output in a binary proprietary format while CruiseControl.NET uses XML in order to generate its reports. Ouch!

Luckily, Microsoft distributes a .NET API that can be used to convert the content of code coverage files produced by Visual Studio into XML. Pheeew!

The library is contained in the Microsoft.VisualStudio.Coverage.Analysis.dll assembly, which can be found in the Visual Studio 2008 Team System installation folder (usually in C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE\PrivateAssemblies). So all I had to do was to add an extra step in the build process to invoke that library and do the conversion.

Since I am using MSBuild to run the build, I encapsulated the code in an MSBuild task which you can find over here at the MSDN Code Gallery. There isn’t really much to it, the actual conversion is easily done in a couple of lines of code:

// You need to specify the directory containing
// the binaries that have been profiled by MSTest
CoverageInfoManager.SymPath = symbolsDirPath;
CoverageInfoManager.ExePath = symbolsDirPath;

// The input file is the binary output produced by MSTest
CoverageInfo info = CoverageInfoManager.CreateInfoFromFile(inputFilePath);
CoverageDS dataSet = info.BuildDataSet(null);
dataSet.WriteXml(outputFilePath);

Then, the task can be invoked from the MSBuild script with:

<!-- Imports the task from the assembly -->
<UsingTask TaskName="ConvertVSCoverageToXml" AssemblyFile="CI.MSBuild.Tasks.dll" />

<!-- The values of the 'OutputPath' and 'TestConfigName' variables
     must be the same as the arguments passed to MSTest.exe
     with the /resultsfile and /runconfig options -->
<ConvertVSCoverageToXml 

    CoverageFiles="$(OutputPath)\$(TestConfigName)\In\$(ComputerName)\data.coverage"

    SymbolsDirectory="$(OutputPath)\$(TestConfigName)\Out"
    OutputDirectory="$(OutputPath)" />

This could easily be achieved in much the same way with an NAnt task, if that’s your build tool of choice.

Download VSCoverageToXml MSBuild Task

/Enrico