How to run Expecto with dotnet test

Expecto is a fantastic test framework and test runner for FSharp. But contrary to the name, the thing I like most about Expecto is that it contains so little magic. Your test project is a simple Console applications and to run you tests you just run the app. No Visual Studio plugins required.

dotnet run

However, recently I wanted to also run my tests using dotnet test to fit into a existing test suit and build script. By default Expecto tests won't be discovered by dotnet test but the good news is it's only two packages and an attribute away from working with both run and test.

I started with an application that used no auto test discovery opting for explicit test registration like the following.

let allTests =
    testList "all-tests" [
        BuilderTests.tests
        Convention.test
        Domain.tests
    ]
    
[<EntryPoint>]
let main argv =
    printfn "Running tests!"   
    runTestsWithArgs config argv allTests

We'll come back to this later, first we need to install some packages.

In order to set up tests with dotnet core we need to add the Test SDK to the project file.

<PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.3.0" />

However this will generate an entry point for your application and because we already have one we'll need to disable that by setting GenerateProgramFile to false in the project file.

<PropertyGroup>
    <GenerateProgramFile>false</GenerateProgramFile>
</PropertyGroup>

After that we'll need to add the package YoloDev.Expecto.TestSdk in order dotnet test to discover Expecto tests.

<PackageReference Include="YoloDev.Expecto.TestSdk" Version="0.8.0" />

This package exposes Expecto Test Attributes for discovery via the Microsoft Test SDK.

Finally, we need to make one change to the Program.fs file, adding the Tests attribute to the tests so they can be discovered.

[<Tests>]
let allTests =
    testList "all-tests" [
        BuilderTests.tests
        Convention.test
        Domain.tests
    ]
    
[<EntryPoint>]
let main argv =
    printfn "Running tests!"   
    runTestsWithArgs config argv allTests

Now when we run dotnet test we see the following:

> dotnet test
Test run for App.Tests.dll(.NETCoreApp,Version=v2.2)
Microsoft (R) Test Execution Command Line Tool Version 16.3.0
Copyright (c) Microsoft Corporation.  All rights reserved.

Starting test execution, please wait...

A total of 1 test files matched the specified pattern.

Test Run Successful.
Total tests: 31
     Passed: 31
 Total time: 1.3619 Seconds

Success!

How to run Expecto with dotnet test

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