Code Coverage with .Net Core and Cobertura

Already I have some routine activity to provide code coverage report for my .Net Core projects to CI. An issue turned out more complex then I appreciate so I decide to provide here the most important steps from the journey

Prerequisites

So, let’s assume that we have some codebase

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dotnet new classlib -n MyBuisLogic

and two test projects: one with unit and another with integration tests

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dotnet new xunit -n MyBuisLogic.Unit.Tests
dotnet new xunit -n MyBuisLogic.Integration.Tests

Add Coverlet

First of all we should add coverlet.collector to both test projects

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cd MyBuisLogic.Unit.Tests && dotnet add package coverlet.collector && cd ..
cd MyBuisLogic.Integration.Tests && dotnet add package coverlet.collector && cd ..

then you should check that your csproj contains something like this:

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<ItemGroup>
    <PackageReference Include="coverlet.collector" Version="1.3.0"/>
    ...
</ItemGroup>

If you add coverlet package using Visual Studio it will be installed with assets filters and your csproj will contain

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<ItemGroup> <PackageReference Include="coverlet.collector" Version="1.3.0"> <PrivateAssets>all</PrivateAssets> <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets> </PackageReference> ... </ItemGroup>

In this case you should remove this additional elements manualy. Otherwise you will have an error "Could not find data collector 'XPlat Code Coverage'"

If you done this right than you can run

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cd MyBuisLogic.Unit.Tests && dotnet test --collect:"XPlat Code Coverage" && cd ..

and you should find out a file TestResults\9b78f4a3-d61c-48d7-8ad7-d4aefe299768\coverage.cobertura.xml in your MyBuisLogic.Unit.Tests folder

Merge Cobertura reports

If your CI system supports collecting reports from multiple Cobertura files, than you’re done. Otherwise (for example in the case of Azure DevOps) you should merge multiple coverage files in one. We will done this with reportgenerator dotnet global tool.

First of all we should install reportgenerator

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dotnet tool install -g dotnet-reportgenerator-globaltool

And now we can merge all our coverage results into one:

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reportgenerator "-reports:.\**\TestResults\**\coverage.cobertura.xml"
"-targetdir:." -reporttypes:Cobertura