run-tests

name	run-tests
description	Run, filter, or troubleshoot .NET tests with `dotnet test`. USE FOR: running all tests in a project or solution; running only a subset (a specific test class, category, or trait) via filters; running a single target framework in a multi-TFM project (`--framework`); producing TRX reports; collecting crash or hang dumps; diagnosing why `dotnet test` fails or uses the wrong argument syntax. Detects the test platform (VSTest vs Microsoft.Testing.Platform) and framework (MSTest/xUnit/NUnit/TUnit), then picks the matching command: the `--` separator on .NET SDK 8/9 vs 10+, the right filter flag (--filter, --filter-class, --filter-trait, --filter-query, --treenode-filter), and TRX/blame flags. DO NOT USE FOR: writing test code (use code-testing-agent), iterating on failing tests without rebuilding (use mtp-hot-reload), CI/CD config, or debugging test logic.
license	MIT

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)

Critical Rules — Avoid Cross-Platform Mistakes

These are the most common agent mistakes. Internalize before proceeding:

Rule	Why
Do NOT use --logger trx for MTP projects	MTP uses --report-trx (requires the TrxReport extension package)
Do NOT use --report-trx for VSTest projects	VSTest uses --logger trx
Do NOT use -- --arg on .NET SDK 10+	SDK 10+ passes MTP args directly: dotnet test --project . --report-trx
Do NOT omit -- on .NET SDK 8/9 with MTP	SDK 8/9 requires the separator: dotnet test -- --report-trx
Do NOT use --filter "ClassName=..." with xUnit v3 on MTP	xUnit v3 on MTP uses --filter-class, --filter-method, --filter-trait
Do NOT use bare positional path on SDK 10+	Use --project <path> or --solution <path> instead
Do NOT use --blame for MTP projects	MTP uses --blame-crash and --blame-hang-timeout separately (each requires its extension package)
Do NOT use --collect "Code Coverage" for MTP	MTP uses --coverage (requires the CodeCoverage extension package)

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

If the prompt names a subset of tests (e.g., "integration tests", "smoke tests", a specific class, a specific TFM), plan to apply the matching filter / --framework in Step 3 — do not run the whole suite.

Step 1: Detect the test platform and framework

1. Run dotnet --version in the project directory to determine the SDK version. This accounts for global.json SDK pinning.
2. Read global.json — on .NET SDK 10+, "test": { "runner": "Microsoft.Testing.Platform" } is the authoritative MTP signal. If present, the project uses MTP and SDK 10+ syntax (no -- separator).
3. Read .csproj, Directory.Build.props, and Directory.Packages.props for framework packages and MTP properties. Always check all three files — MTP properties are frequently set in Directory.Build.props rather than individual .csproj files.
4. For full detection logic (SDK 8/9 signals, framework identification), see the platform-detection skill.

What to look for in each file:

File	Look for	Indicates
global.json	"test": { "runner": "Microsoft.Testing.Platform" }	MTP on SDK 10+
global.json	"sdk": { "version": "..." }	SDK version (determines -- separator behavior)
.csproj	<TestingPlatformDotnetTestSupport>true	MTP on SDK 8/9
.csproj	MSTest, xunit.v3, NUnit, TUnit packages	Framework identity
.csproj	Microsoft.NET.Test.Sdk + test adapter	VSTest (unless overridden by MTP signals above)
.csproj	<TargetFrameworks> (plural)	Multi-TFM — may need --framework
Directory.Build.props	<TestingPlatformDotnetTestSupport>true	MTP on SDK 8/9 (often set here, not in .csproj)
Directory.Packages.props	Centrally managed test package versions	Framework identity for CPM repos

Quick detection summary:

Signal	Means
global.json has "test": { "runner": "Microsoft.Testing.Platform" }	MTP on SDK 10+ — pass args directly, no --
<TestingPlatformDotnetTestSupport>true in csproj or Directory.Build.props	MTP on SDK 8/9 — pass args after --
Neither signal present	VSTest

Step 2: Run tests

VSTest (any .NET SDK version)

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)
--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 --:

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 --:

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

Examples:

# 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.

Important: dotnet test/MSBuild flags such as --framework, --no-build, --configuration, and --verbosity are consumed by dotnet test itself (they drive restore/build/host selection) and always go BEFORE --, regardless of platform or SDK. Only MTP test-platform arguments go after -- on SDK 8/9. For example: dotnet test --framework net9.0 -- --report-trx (built-in flag before --, MTP extension flag after).

Built-in flags (always available):

Flag	Description
--results-directory <DIR>	Directory for test result output
--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)
--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:

# 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 the filter-syntax skill 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). For a single combined expression (e.g., a class-name pattern AND a trait), use --filter-query with the xUnit v3 query filter language: path segments /<assembly>/<namespace>/<class>/<method> with * wildcards and a [Trait=Value] qualifier — for example dotnet test -- --filter-query "/*/*/*IntegrationTests*/*[Category=Smoke]". See the filter-syntax skill for the full query language.
• MTP -- TUnit: Uses --treenode-filter with path-based syntax

When the user names a test category, trait, or group

When the prompt names a subset of tests by category (e.g., "integration tests", "unit tests", "smoke tests", "fast tests"), do not run all tests — translate the user's vocabulary into the platform-appropriate filter:

1. Inspect the test source files for filter-attribute annotations that match the named group:

   Framework	Attribute	Filter property
   MSTest	[TestCategory("Integration")]	TestCategory
   NUnit	[Category("Integration")]	TestCategory (mapped)
   xUnit v2	[Trait("Category", "Integration")]	Category
   xUnit v3	[Trait("Category", "Integration")]	Category (use --filter-trait)
   TUnit	[Category("Integration")]	Category

2. Build the filter expression and combine it with the platform-correct invocation. For "run the integration tests" against an MSTest project:

   Platform	SDK	Command
   VSTest (MSTest)	any	dotnet test --filter "TestCategory=Integration"
   MTP (MSTest)	8 or 9	dotnet test -- --filter "TestCategory=Integration"
   MTP (MSTest)	10+	dotnet test --filter "TestCategory=Integration"
   MTP (xUnit v3)	8 or 9	dotnet test -- --filter-trait "Category=Integration"
   MTP (xUnit v3)	10+	dotnet test --filter-trait "Category=Integration"
   MTP (TUnit)	8 or 9	dotnet test -- --treenode-filter "/*/*/*/*[Category=Integration]"

3. If you cannot find a matching attribute, ask the user to confirm the category name or fall back to a name-pattern filter (e.g., --filter "FullyQualifiedName~Integration").

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
• When the user named a test category/trait/group, the appropriate filter was applied (not "run all tests")
• 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 -- --arg separator on .NET SDK 10+	SDK 10+ passes MTP args directly — do NOT use -- separator
Using --logger trx for MTP or --report-trx for VSTest	Each platform has its own TRX flag — check the Critical Rules table
Only checking .csproj for MTP signals	Always check Directory.Build.props and Directory.Packages.props too — MTP properties are frequently set there
Using bare positional path argument on SDK 10+	SDK 10+ requires named flags: --project <path> or --solution <path>

Troubleshooting

Common error messages and how to resolve them:

Error	Cause	Fix
No test is available or No test matches the given testcase filter	Wrong filter syntax for the platform/framework, or tests not discovered	Verify filter syntax matches the platform (see filter-syntax skill). For discovery issues, check that the test SDK and adapter packages are installed
The --report-trx option is unrecognized	MTP extension package not referenced, or using MTP flag on a VSTest project	Add <PackageReference Include="Microsoft.Testing.Extensions.TrxReport" /> for MTP, or use --logger trx for VSTest
The --blame-hang-timeout option is unrecognized	Missing HangDump extension on MTP	Add <PackageReference Include="Microsoft.Testing.Extensions.HangDump" />
error NETSDK1045: The current .NET SDK does not support targeting .NET X.0	SDK version in global.json doesn't match the project's target framework	Update global.json SDK version or install the required SDK
The test runner process exited with non-zero exit code	MTP test host crashed or test failure	Run with --blame-crash (MTP) or --blame (VSTest) to collect a crash dump for diagnosis
No test source files were found / No test project found	dotnet test can't find a test project in the given path	Specify the path explicitly: dotnet test <path/to/project.csproj> (VSTest) or dotnet test --project <path> (SDK 10+)
Tests discovered but 0 executed	Filter expression matches no tests	Double-check filter property names and values. Common typo: TestCategory (MSTest) vs Category (NUnit) vs trait syntax (xUnit)
Using -- for MTP args on .NET SDK 10+	On .NET 10+, MTP args are passed directly: dotnet test --project . --blame-hang-timeout 5min — do NOT use -- --blame-hang-timeout
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. On .NET SDK 10+ use dotnet test; on older SDKs use dotnet run since VSTest-mode dotnet test does not support TUnit