---
name: tunit
description: Write or troubleshoot tests using TUnit, TUnit.Assertions, or TUnit.Mocks, or migrate tests to TUnit. Routes to task-specific official documentation. Use only for tasks involving these packages or migration to TUnit.
license: MIT
---

# TUnit

Use this skill to find the TUnit guidance needed for the current task. Fetch documentation with an available web tool or HTTP client; network access is required. The documentation contains the API details and examples; do not load the whole site.

## Load only what the task needs

1. Check the relevant project files for TUnit package versions, target frameworks, and the SDK/test runner in `global.json`. Include centrally managed package versions when present. Preserve the project's versions unless an upgrade is requested or necessary and explained.
2. Choose the closest topic below and fetch that Markdown page before choosing APIs or commands. Start with one page; fetch another only when the task needs it. Skip pages already available in the conversation unless they need refreshing.
3. For an unlisted topic or a broken route, fetch [the documentation index](https://tunit.dev/llms.txt), search it for the feature or diagnostic, then fetch only the matching page. Do not fetch `llms-full.txt` or crawl every link.
4. Follow related links only to resolve a specific gap. Prefer the `.md` version: remove a trailing slash and append `.md` to an HTML documentation path, before any fragment. Keep existing `.md` paths unchanged. Resolve relative links against the fetched page's URL.
5. Apply the relevant example to the existing project and run a focused build or test when making code changes. Cite the documentation used. If current documentation differs from the installed API, check version-matched source or local API evidence before proposing an upgrade. If fetching fails, use available local documentation and state what could not be verified; do not guess APIs.

## Topic routes

Choose the link that matches the task; these are alternatives, not a reading checklist.

| Task | Documentation |
| --- | --- |
| Create or configure a project | [Installation](https://tunit.dev/docs/getting-started/installation.md) |
| Write a basic test | [First test](https://tunit.dev/docs/getting-started/writing-your-first-test.md) |
| Assertions, exceptions, or assertion composition | [Assertions](https://tunit.dev/docs/assertions/getting-started.md) |
| Parameterized tests | [Arguments](https://tunit.dev/docs/writing-tests/arguments.md), [method data](https://tunit.dev/docs/writing-tests/method-data-source.md), or [matrix data](https://tunit.dev/docs/writing-tests/matrix-tests.md) |
| Setup, teardown, or hooks | [Lifecycle](https://tunit.dev/docs/writing-tests/lifecycle.md) |
| Fixtures, shared resources, or dependency injection | [Class data sources](https://tunit.dev/docs/writing-tests/class-data-source.md) or [dependency injection](https://tunit.dev/docs/writing-tests/dependency-injection.md) |
| Concurrency or dependencies between tests | [Parallelism](https://tunit.dev/docs/execution/parallelism.md) or [ordering](https://tunit.dev/docs/writing-tests/ordering.md) |
| Run tests or select tests | [Running tests](https://tunit.dev/docs/getting-started/running-your-tests.md) or [filters](https://tunit.dev/docs/execution/test-filters.md) |
| Migrate an existing suite | [xUnit](https://tunit.dev/docs/migration/xunit.md), [NUnit](https://tunit.dev/docs/migration/nunit.md), or [MSTest](https://tunit.dev/docs/migration/mstest.md), matching the source framework |
| Mocking | [TUnit.Mocks](https://tunit.dev/docs/writing-tests/mocking.md) |
| Aspire integration testing | [Aspire](https://tunit.dev/docs/examples/aspire.md) |
| ASP.NET Core integration testing | [ASP.NET Core](https://tunit.dev/docs/examples/aspnet.md) |
| Playwright browser testing | [Playwright](https://tunit.dev/docs/examples/playwright.md) |
| Testcontainers and container fixtures | [ASP.NET Core integration examples](https://tunit.dev/docs/examples/aspnet.md) (see "With Testcontainers") |
| Native AOT, trimming, or reflection mode | [AOT compatibility](https://tunit.dev/docs/writing-tests/aot.md) or [engine modes](https://tunit.dev/docs/execution/engine-modes.md) |
| Custom assertions | [Assertion source generators](https://tunit.dev/docs/assertions/extensibility/source-generator-assertions.md) or [custom assertion implementations](https://tunit.dev/docs/assertions/extensibility/custom-assertions.md) |
| Custom data sources | [Data source generators](https://tunit.dev/docs/extending/data-source-generators.md) |
| Event receivers | [Event subscribing](https://tunit.dev/docs/writing-tests/event-subscribing.md) |
| TestContext and test metadata | [Test context](https://tunit.dev/docs/writing-tests/test-context.md) |
| Diagnostics, output, or tracing | [Logging](https://tunit.dev/docs/extending/logging.md), [test artifacts](https://tunit.dev/docs/writing-tests/artifacts.md), or [OpenTelemetry](https://tunit.dev/docs/examples/opentelemetry.md) |
| Cancellation | [Cancelling a test](https://tunit.dev/docs/execution/cancellation.md) |
| Discovery, build, or execution failures | [Troubleshooting](https://tunit.dev/docs/troubleshooting.md) |

For other topics, such as analyzers or framework-specific integrations, use the index selectively.

## Essential distinctions

- Await TUnit assertions, for example `await Assert.That(actual).IsEqualTo(expected);`.
- Tests run in parallel by default. Account for shared mutable state and resource lifetimes.
- TUnit uses Microsoft.Testing.Platform and `--treenode-filter`. Match command syntax to the project's SDK and runner mode; do not substitute VSTest `--filter` or assume every `dotnet test` invocation needs a `--` separator.
- Source-generated discovery is the default; reflection mode also exists. Check the relevant documentation when changing discovery or Native AOT behavior.
- TUnit.Assertions and TUnit.Mocks also work with other test frameworks. Using them alone does not require changing the project's test runner.