1. Introduction.
I’ve been struggling for some time to make OpenCover work with .NET Core projects, so I’ve decided to document a working example. This is basically an aggregation of hints and answers I found on the Web (especially in here)
2. Working example.
If you run an OpenCover with the same arguments you were running it for a classic framework, you will end up with something like this
As you can see the coverage was not calculated and OpenCover is complaining about a missing PDBs. In order to fix that we have to do two things. First of all, we have to build the project with a full PDBs
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dotnet build "PathToYourSolution.sln" /p:DebugType=Full |
And then run OpenCover with and -oldStyle switch
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OpenCover.Console.exe -target:"C:/Program Files/dotnet/dotnet.exe" -targetargs:"test \"PathToTestProject.csproj\" --configuration Debug --no-build" -filter:"+[*]* -[*.Tests*]*" -oldStyle -register:user -output:"OpenCover.xml" |
From now on, OpenCover recognizes PDB files and the code coverage is calculated correctly
3. Cake script.
As we use a Cake as our build automation tool I’ve also prepared a sample script for generating a code coverage. The core part of the script looks as follows
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// rest of the code omitted for brevity Task("Build") .IsDependentOn("Restore-NuGet-Packages") .Does(() => { DotNetCoreBuild(paths.Files.Solution.ToString(), new DotNetCoreBuildSettings { Configuration = parameters.Configuration, ArgumentCustomization = arg => arg.AppendSwitch("/p:DebugType","=","Full") }); }); Task("Run-Tests") .IsDependentOn("Build") .Does(() => { var success = true; var openCoverSettings = new OpenCoverSettings { OldStyle = true, MergeOutput = true } .WithFilter("+[*]* -[*.Tests*]*"); foreach(var project in paths.Files.TestProjects) { try { var projectFile = MakeAbsolute(project).ToString(); var dotNetTestSettings = new DotNetCoreTestSettings { Configuration = parameters.Configuration, NoBuild = true }; OpenCover(context => context.DotNetCoreTest(projectFile, dotNetTestSettings), paths.Files.TestCoverageOutput, openCoverSettings); } catch(Exception ex) { success = false; Error("There was an error while running the tests", ex); } } ReportGenerator(paths.Files.TestCoverageOutput, paths.Directories.TestResults); if(success == false) { throw new CakeException("There was an error while running the tests"); } }); |
Notice that script is able to merge code coverage results from multiple test projects thanks to MergeOutput flag passed to OpenCover.
Full sources of that script (along with a dotnet vstest alternative approach) can be found here.