# The MSTest Framework

MSTest is Microsoft's testing framework for .NET. A test runner finds and runs your tests; a test class holds the tests for one class, in a test project of its own.

Apprentice · Unit Testing · C# · Updated November 3, 2026

## After this lesson you can

- Explain what a testing framework, a test runner, a test project and a test class are

## Key takeaways

- A testing framework such as MSTest comes with a test runner: it finds every test, runs each one and reports which passed and which failed.
- Start the runner with Test > Run All Tests in Visual Studio, or `dotnet test` in the terminal.
- Tests live in a test project of their own, named after the app with `.Tests` on the end, so they never ship with your app.
- Each class you test gets its own test class, named after it with `Tests` on the end: `TelevisionTests` tests `Television`.

To test a class, something has to create its objects, call their methods and check the results. You could write a console program for each class you want to test, but you'd be writing the same kind of program over and over. A **testing framework** writes that program once, for everyone.

**MSTest** is Microsoft's testing framework for .NET, and the one this course uses. (You may also meet **xUnit** and **NUnit**: they do the same job, with slightly different names for things.)

## The test runner

MSTest comes with a **test runner**: a ready-made program that finds every test in your project, runs each one, and reports which passed and which failed. You never write it; you start it:

- In Visual Studio: **Test > Run All Tests**, and the results appear in **Test Explorer**.
- In the terminal: `dotnet test`.

```text
Passed!  - Failed:     0, Passed:    14, Skipped:     0, Total:    14, Duration: 52 ms - TvRemote.Tests.dll (net10.0)
```

## Test projects and test classes

Tests live in a **test project** of their own, beside the project they test, so the tests never ship with your app. Name it after the project, with `.Tests` on the end:

```text
TvRemote/              the app: Television.cs, Program.cs
TvRemote.Tests/        the tests: TelevisionTests.cs
TvRemote.slnx          one solution holds both
```

Inside it, each class you test gets its own **test class**, named after it with `Tests` on the end. `TelevisionTests` holds every test for `Television`:

![TelevisionTests verifies the logic of Television](https://fsdtrainingmedia.blob.core.windows.net/public/images/2026/09/7032ae4fc65f4686bd00dedfb0c73012.png "TelevisionTests verifies the logic of Television")

| Part | Who writes it | What it does |
|---|---|---|
| Test runner | MSTest | Finds and runs every test, and reports the results |
| Test project | You, once | Holds the tests, apart from the app |
| Test class | You, one per class | Holds the tests for one class |
| Test method | You, one per scenario | Tests one thing |

## Check yourself

1 question to try on the lesson page.

## So what

The runner does the running and reporting; your job is only the tests. With one test class per class, every class in your app gets its own safety net.

## Key terms

- [MSTest](https://www.ask-codey.com/glossary/mstest)
- [Test Runner](https://www.ask-codey.com/glossary/test-runner)
- [Test Project](https://www.ask-codey.com/glossary/test-project)

## Cheat sheets

- [The MSTest Framework](https://www.ask-codey.com/cheat-sheets/unit-testing-with-mstest-the-mstest-framework-cheat-sheet)

Source: https://www.ask-codey.com/lessons/unit-testing-with-mstest-the-mstest-framework