Generating code coverage from integration tests with dotCover

#csharp #dotnet #testing #tutorial

Sometimes your integration tests aren't written in the same language as your application (especially e2e tests) and it gets hard to collect code coverage for the main application. I currently have this exact issue where I have an application written in C# using dotnet core 3.1, and I have my integration tests written in JavaScript. It's really easy to get the code coverage for unit tests in C#, but it becomes a little harder when my tests aren't written in C#.

That's where dotCover comes in.

NOTE: dotCover is not free to use. They do have a trial, but otherwise you need a ReSharper Ultimate subscription for personal or commercial use. I'm personally a huge fan of JetBrains and already subscribe to their full suite of products.

First we'll download dotCover, and place it in our path. It will work in both Windows and Unix environments, and all the commands I will write here are for Windows. After extracting the file, I'm going to add to my path using the Edit System Environment Variables. If you set it up successfully, you should be able to run dotcover in PowerShell and see this output. If you're running on Unix, you might have to add +x to the dotCover.sh and you might need to call it from the terminal as dotCover.sh instead of just dotCover

Now that we have access to run dotcover, we can start our application with it and test against or (or just run against it to potentially see where we have dead code).

All the console commands can be found here.

First off we're going to start our set our application up to get ready to start with this command.

dotcover cover --targetExecutable="bin\Debug\netcoreapp3.1\win-x64\YourApplicationName.exe" --output="report.html" --reportType="HTML" --startInstance="1"

Let's go over the args one at a time.

--targetExecutable is the executable you want to test against. For me this is my Web Api.

--output is just that, it's the name of the file to open the coverage report. For now, report.html will suffice.

--reportType is also pretty simple. For me I like the pretty HTML it outputs so that's what I use. Here's the rest you can use HTML|JSON|XML|DetailedXML|NDependXML.

--startInstance="1" is going to set our application to be run by dotcover with the identifier 1. This is so that if we need to something before we start our application, we can. For me, I need to set up my JavaScript tests, so that's what I do here, but you can do whatever you need.

Now that our instance is prime and ready, we're ready to start our application via dotcover. This is done by the send command.

So we'll run dotcover send --Instance="1" --Command="Cover" which will start our app.

--Instance="1" is denote which instance we're sending it to

--Command="Cover" is to tell it to start

Next we can start our tests that run against our app. For me this would be a simple yarn start

After that's over we need to tell the runner that it's done and to output the files. All we have to do is send another command to our instance with dotcover send --Instance="1" --Command='GetSnapshotAndKillChildren"

It should say that it send the command successfully, and you should have your outputs!