dotnet core code coverage using AltCover and ReportGenerator

AltCover is awesome!!

Code coverage for dotnet core

Some of the traditional code coverage tools for .Net have still not yet been ported for dotnetcore.

A while back, I was tasked in finding a code coverage tool to integrate into our build process. I found that with altcover, rather than hooking into the .net profiling API at run-time, it works by weaving the same sort of extra IL into the assemblies of interest ahead of execution.

AltCover can be included as a NuGet package, or you can install it as a global tool, which is handy for say build agents.

How to install

Globally

dotnet tool install --global altcover.global

Project

dotnet add package AltCover

How to run

dotnet test /p:AltCover=true

This will output a coverage.xml file in opencover format.

You can then run ReportGenerator on the coverage file to genetate a UI to visualise the data.

Here is a full example of the command we use, which we then include as a coverage report inside our build process.

dotnet test /p:AltCover=true /p:AltCoverXmlreport=".\coverage.xml" /p:AltCoverAssemblyFilter="NUnit" /p:AltCoverThreshold=80 /p:AltCoverAttributeFilter="ExcludeFromCodeCoverage"
reportgenerator -reports:src/SalesImportApi.Tests/coverage.xml -targetdir:./coverage