# Run Tests

> Runs .NET tests with dotnet test. Use when user says "run tests", "execute tests", "dotnet test", "test filter", "tests not running", or needs to detect the test platform (VSTest or Microsoft.Testing.Platform), identify the test framework, apply test filters, or troubleshoot test execution failures. Covers MSTest, xUnit, NUnit, and TUnit across both VSTest and MTP platforms. DO NOT USE FOR: writing or generating test code, CI/CD pipeline configuration, or debugging failing test logic.

- Skill: `majiayu000/run-tests-4` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds add majiayu000/run-tests-4`
- Raw SKILL.md: https://api.skillmd.com/api/skills/majiayu000/run-tests-4/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: DevOps & Infra
- Author: majiayu000 (https://skillmd.com/u/majiayu000)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/majiayu000/run-tests-4

---


# Run .NET Tests

Detect the test platform and framework, run tests, and apply filters using `dotnet test`.

## When to Use

- User wants to run tests in a .NET project
- User needs to run a subset of tests using filters
- User needs help detecting which test platform (VSTest vs MTP) or framework is in use
- User wants to understand the correct filter syntax for their setup

## When Not to Use

- User needs to write or generate test code (use `writing-mstest-tests` for MSTest, or general coding assistance for other frameworks)
- User needs to migrate from VSTest to MTP (use `migrate-vstest-to-mtp`)
- User wants to iterate on failing tests without rebuilding (use `mtp-hot-reload`)
- User needs CI/CD pipeline configuration (use CI-specific skills)
- User needs to debug a test (use debugging skills)

## Inputs

| Input | Required | Description |
|-------|----------|-------------|
| Project or solution path | No | Path to the test project (.csproj) or solution (.sln). Defaults to current directory. |
| Filter expression | No | Filter expression to select specific tests |
| Target framework | No | Target framework moniker to run against (e.g., `net8.0`) |

## Workflow

### Quick Reference

| Platform | SDK | Command pattern |
|----------|-----|----------------|
| VSTest | Any | `dotnet test [<path>] [--filter <expr>] [--logger trx]` |
| MTP | 8 or 9 | `dotnet test [<path>] -- <MTP_ARGS>` |
| MTP | 10+ | `dotnet test --project <path> <MTP_ARGS>` |

**Detection files to always check** (in order): `global.json` → `.csproj` → `Directory.Build.props` → `Directory.Packages.props`

### Step 1: Detect the test platform and framework

1. Run `dotnet --version` to determine the .NET SDK version
2. Read `global.json`, `.csproj`, `Directory.Build.props`, and `Directory.Packages.props`
3. Follow the detection procedure in [references/platform-detection.md](references/platform-detection.md) to determine:
   - **Test framework**: MSTest, xUnit, NUnit, or TUnit
   - **Test platform**: VSTest or Microsoft.Testing.Platform (MTP)

### Step 2: Run tests

#### VSTest (any .NET SDK version)

```bash
dotnet test [<PROJECT> | <SOLUTION> | <DIRECTORY> | <DLL> | <EXE>]
```

Common flags:

| Flag | Description |
|------|-------------|
| `--framework <TFM>` | Target a specific framework in multi-TFM projects (e.g., `net8.0`) |
| `--no-build` | Skip build, use previously built output |
| `--filter <EXPRESSION>` | Run selected tests (see [Step 3](#step-3-run-filtered-tests)) |
| `--logger trx` | Generate TRX results file |
| `--collect "Code Coverage"` | Collect code coverage using Microsoft Code Coverage (built-in, always available) |
| `--blame` | Enable blame mode to detect tests that crash the host |
| `--blame-crash` | Collect a crash dump when the test host crashes |
| `--blame-hang-timeout <duration>` | Abort test if it hangs longer than duration (e.g., `5min`) |
| `-v <level>` | Verbosity: `quiet`, `minimal`, `normal`, `detailed`, `diagnostic` |

#### MTP with .NET SDK 8 or 9

With `<TestingPlatformDotnetTestSupport>true</TestingPlatformDotnetTestSupport>`, `dotnet test` bridges to MTP but uses VSTest-style argument parsing. MTP-specific arguments must be passed after `--`:

```bash
dotnet test [<PROJECT> | <SOLUTION> | <DIRECTORY> | <DLL> | <EXE>] -- <MTP_ARGUMENTS>
```

#### MTP with .NET SDK 10+

With the `global.json` runner set to `Microsoft.Testing.Platform`, `dotnet test` natively understands MTP arguments without `--`:

```bash
dotnet test
    [--project <PROJECT_OR_DIRECTORY>]
    [--solution <SOLUTION_OR_DIRECTORY>]
    [--test-modules <EXPRESSION>]
    [<MTP_ARGUMENTS>]
```

Examples:

```bash
# Run all tests in a project
dotnet test --project path/to/MyTests.csproj

# Run all tests in a directory containing a project
dotnet test --project path/to/

# Run all tests in a solution (sln, slnf, slnx)
dotnet test --solution path/to/MySolution.sln

# Run all tests in a directory containing a solution
dotnet test --solution path/to/

# Run with MTP flags
dotnet test --project path/to/MyTests.csproj --report-trx --blame-hang-timeout 5min
```

> **Note**: The .NET 10+ `dotnet test` syntax does **not** accept a bare positional argument like the VSTest syntax. Use `--project`, `--solution`, or `--test-modules` to specify the target.

#### Common MTP flags

These flags apply to MTP on both SDK versions. On SDK 8/9, pass after `--`; on SDK 10+, pass directly.

**Built-in flags (always available):**

| Flag | Description |
|------|-------------|
| `--no-build` | Skip build, use previously built output |
| `--framework <TFM>` | Target a specific framework in multi-TFM projects |
| `--diagnostic` | Enable diagnostic logging for the test platform |
| `--diagnostic-output-directory <DIR>` | Directory for diagnostic log output |

**Extension-dependent flags (require the corresponding extension package to be registered):**

| Flag | Requires | Description |
|------|----------|-------------|
| `--filter <EXPRESSION>` | Framework-specific (not all frameworks support this) | Run selected tests (see [Step 3](#step-3-run-filtered-tests)) |
| `--report-trx` | `Microsoft.Testing.Extensions.TrxReport` | Generate TRX results file |
| `--report-trx-filename <FILE>` | `Microsoft.Testing.Extensions.TrxReport` | Set TRX output filename |
| `--blame-hang-timeout <duration>` | `Microsoft.Testing.Extensions.HangDump` | Abort test if it hangs longer than duration (e.g., `5min`) |
| `--blame-crash` | `Microsoft.Testing.Extensions.CrashDump` | Collect a crash dump when the test host crashes |
| `--coverage` | `Microsoft.Testing.Extensions.CodeCoverage` | Collect code coverage using Microsoft Code Coverage |

> Some frameworks (e.g., MSTest) bundle common extensions by default. Others may require explicit package references. If a flag is not recognized, check that the corresponding extension package is referenced in the project.

#### Alternative MTP invocations

MTP test projects are standalone executables. Beyond `dotnet test`, they can be run directly:

```bash
# Build and run
dotnet run --project <PROJECT_PATH>

# Run a previously built DLL
dotnet exec <PATH_TO_DLL>

# Run the executable directly (Windows)
<PATH_TO_EXE>
```

These alternative invocations accept MTP command line arguments directly (no `--` separator needed).

### Step 3: Run filtered tests

See [references/filter-syntax.md](references/filter-syntax.md) for the complete filter syntax for each platform and framework combination. Key points:

- **VSTest** (MSTest, xUnit v2, NUnit): `dotnet test --filter <EXPRESSION>` with `=`, `!=`, `~`, `!~` operators
- **MTP — MSTest and NUnit**: Same `--filter` syntax as VSTest; pass after `--` on SDK 8/9, directly on SDK 10+
- **MTP — xUnit v3**: Uses `--filter-class`, `--filter-method`, `--filter-trait` (not VSTest expression syntax)
- **MTP — TUnit**: Uses `--treenode-filter` with path-based syntax

## Validation

- [ ] Test platform (VSTest or MTP) was correctly identified
- [ ] Test framework (MSTest, xUnit, NUnit, TUnit) was correctly identified
- [ ] Correct `dotnet test` invocation was used for the detected platform and SDK version
- [ ] Filter expressions used the syntax appropriate for the platform and framework
- [ ] Test results were clearly reported to the user

## Common Pitfalls

| Pitfall | Solution |
|---------|----------|
| Missing `Microsoft.NET.Test.Sdk` in a VSTest project | Tests won't be discovered. Add `<PackageReference Include="Microsoft.NET.Test.Sdk" />` |
| Using VSTest `--filter` syntax with xUnit v3 on MTP | xUnit v3 on MTP uses `--filter-class`, `--filter-method`, etc. — not the VSTest expression syntax |
| Passing MTP args without `--` on .NET SDK 8/9 | Before .NET 10, MTP args must go after `--`: `dotnet test -- --report-trx` |
| Using `--` for MTP args on .NET SDK 10+ | On .NET 10+, MTP args are passed directly: `dotnet test --report-trx` (using `--` still works but is unnecessary) |
| Multi-TFM project runs tests for all frameworks | Use `--framework <TFM>` to target a specific framework |
| `global.json` runner setting ignored | Requires .NET 10+ SDK. On older SDKs, use `<TestingPlatformDotnetTestSupport>` MSBuild property instead |
| TUnit `--treenode-filter` not recognized | TUnit is MTP-only and requires `dotnet run`, not `dotnet test` with VSTest |