Measuring the coverage of unit tests is an important topic because we need to check the design of the tests and the scope in the code of them.

Coverlet is an amazing tool to measure the coverage of unit tests in .NET projects.

Coverlet is completely opensource and free. it supports .NET and .NET Core and you can add it as a NuGet Package.

dotnet add package coverlet.collector

dotnet add package coverlet.msbuild

dotnet tool install --global coverlet.console

dotnet test --collect:"XPlat Code Coverage"

First, we have to add the NuGet within an existing unit test project (MSTest, xUnit, etc..). Coverlet has many ways to use it but I recommend to use MSBuild.

dotnet add package coverlet.msbuild

after that, we can use easily the integration between MSBuild and coverlet to run the test and measure the coverage with the following command:

dotnet test /p:CollectCoverage=true

you will get the following result:

In the first column from left to right we can see the list of modules covered. In the column 'Line', we get the percentage of lines checked after running the tests and it's the same for 'Branch'(statements) and 'Method'(functions inside the classes).

Coverlet generates a file coverage.json that contains the whole information displayed in the console. You can consume this file with your own application.

Try it out!