Filter Syntax — Agent Skill by .NET (Microsoft)

From the author

Reference-only filter syntax for VSTest and MTP with MSTest, NUnit, xUnit v3, and TUnit. Load only after the platform/framework is known and a consumer needs to create or translate a filter. Do not load for unfiltered runs or platform detection. Used by run-tests and mtp-hot-reload; never invoke directly.

— the description by .NET (Microsoft)

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides a comprehensive reference for test filtering syntax used in various .NET testing frameworks and runners. It covers the standard VSTest filter expressions, MTP-specific flags for xUnit v3, and the path-based filtering used by TUnit. It also includes guidance on translating legacy VSTest filters to the native xUnit v3 MTP syntax, ensuring developers can accurately target specific tests during execution.

What it does

Defines filter operators and combinators for VSTest-compatible frameworks.
Details framework-specific filter flags for xUnit v3 on MTP.
Explains the path-based tree node filtering syntax for TUnit.
Provides a mapping table for translating VSTest filters to xUnit v3 MTP syntax.
Lists supported properties for MSTest, xUnit, and NUnit.
Outlines the use of query filter language for complex xUnit v3 test selection.

When to use it

When you need to construct a filter expression for running a subset of tests.
When migrating existing VSTest-based test suites to xUnit v3 on MTP.
When you need to filter tests by specific traits, categories, or namespaces.
When debugging why a test filter is not selecting the expected tests.

Advantages

Centralizes disparate filtering syntaxes into a single reference.
Simplifies the migration path from VSTest to modern MTP-based test runners.
Provides clear examples for both simple and complex test selection scenarios.
Reduces trial-and-error when configuring test execution pipelines.

Usage examples

“How do I run only integration tests in my MSTest project using VSTest?”: Use the command: dotnet test --filter "TestCategory=Integration"
“What is the equivalent of a VSTest filter for xUnit v3 on MTP?”: xUnit v3 uses specific flags like --filter-class or --filter-trait instead of the generic --filter expression.
“How do I filter TUnit tests by a custom property?”: Use the --treenode-filter flag with the property syntax, for example: --treenode-filter "/*/*/*/*[Category=Smoke]"

Install

Download the skill as a ZIP:
https://autogineer.com/agent-skills/dotnet/filter-syntax/download

Unzip it into the cross-client skills folder of your project:

mkdir -p .agents/skills && unzip filter-syntax.zip -d .agents/skills

Documentation by .NET (Microsoft)

Test Filter Syntax Reference

Filter syntax depends on the platform and test framework.

VSTest filters (MSTest, xUnit v2, NUnit on VSTest)

dotnet test --filter <EXPRESSION>

Expression syntax: <Property><Operator><Value>[|&<Expression>]

Operators:

Operator	Meaning
`=`	Exact match
`!=`	Not exact match
`~`	Contains
`!~`	Does not contain

Combinators: | (OR), & (AND). Parentheses for grouping: (A|B)&C

Supported properties by framework:

Framework	Properties
MSTest	`FullyQualifiedName`, `Name`, `ClassName`, `Priority`, `TestCategory`
xUnit	`FullyQualifiedName`, `DisplayName`, `Traits`
NUnit	`FullyQualifiedName`, `Name`, `Priority`, `TestCategory`

An expression without an operator is treated as FullyQualifiedName~<value>.

Examples (VSTest):

# Run tests whose name contains "LoginTest"
dotnet test --filter "Name~LoginTest"

# Run a specific test class
dotnet test --filter "ClassName=MyNamespace.MyTestClass"

# Run tests in a category
dotnet test --filter "TestCategory=Integration"

# Exclude a category
dotnet test --filter "TestCategory!=Slow"

# Combine: class AND category
dotnet test --filter "ClassName=MyNamespace.MyTestClass&TestCategory=Unit"

# Either of two classes
dotnet test --filter "ClassName=MyNamespace.ClassA|ClassName=MyNamespace.ClassB"

MTP filters — MSTest and NUnit

MSTest and NUnit on MTP use the same --filter syntax as VSTest (same properties, operators, and combinators). The only difference is how the flag is passed:

# .NET SDK 8/9 (after --)
dotnet test -- --filter "Name~LoginTest"

# .NET SDK 10+ (direct)
dotnet test --filter "Name~LoginTest"

MTP filters — xUnit (v3)

xUnit v3 on MTP uses framework-specific filter flags instead of the generic --filter expression:

Flag	Description
`--filter-class "name"`	Run all tests in a given class
`--filter-not-class "name"`	Exclude all tests in a given class
`--filter-method "name"`	Run a specific test method
`--filter-not-method "name"`	Exclude a specific test method
`--filter-namespace "name"`	Run all tests in a namespace
`--filter-not-namespace "name"`	Exclude all tests in a namespace
`--filter-trait "name=value"`	Run tests with a matching trait
`--filter-not-trait "name=value"`	Exclude tests with a matching trait

Multiple values can be specified with a single flag: --filter-class Foo Bar.

# .NET SDK 8/9
dotnet test -- --filter-class "MyNamespace.LoginTests"

# .NET SDK 10+
dotnet test --filter-class "MyNamespace.LoginTests"

# Combine: namespace + trait
dotnet test --filter-namespace "MyApp.Tests.Integration" --filter-trait "Category=Smoke"

xUnit v3 query filter language

For complex expressions, use --filter-query with a path-segment syntax:

/<assemblyFilter>/<namespaceFilter>/<classFilter>/<methodFilter>[traitName=traitValue]

Each segment matches against: assembly name, namespace, class name, method name. Use * for "match all" in any segment. Documentation: https://xunit.net/docs/query-filter-language

# xUnit.net v3 MTP — using query language (assembly/namespace/class/method[trait])
dotnet test -- --filter-query "/*/*/*IntegrationTests*/*[Category=Smoke]"

MTP filters — TUnit

TUnit uses --treenode-filter with a path-based syntax:

--treenode-filter "/<Assembly>/<Namespace>/<ClassName>/<TestName>"

Wildcards (*) are supported in any segment. Filter operators can be appended to test names for property-based filtering.

Operator	Meaning
`*`	Wildcard match
`=`	Exact property match (e.g., `[Category=Unit]`)
`!=`	Exclude property value
`&`	AND (combine conditions)
`\|`	OR (within a segment, requires parentheses)

Examples (TUnit):

# All tests in a class
dotnet run --treenode-filter "/*/*/LoginTests/*"

# A specific test
dotnet run --treenode-filter "/*/*/*/AcceptCookiesTest"

# By namespace prefix (wildcard)
dotnet run --treenode-filter "/*/MyProject.Tests.Api*/*/*"

# By custom property
dotnet run --treenode-filter "/*/*/*/*[Category=Smoke]"

# Exclude by property
dotnet run --treenode-filter "/*/*/*/*[Category!=Slow]"

# OR across classes
dotnet run --treenode-filter "/*/*/(LoginTests)|(SignupTests)/*"

# Combined: namespace + property
dotnet run --treenode-filter "/*/MyProject.Tests.Integration/*/*/*[Priority=Critical]"

VSTest → MTP filter translation (for migration)

MSTest, NUnit, and xUnit.net v2 (with YTest.MTP.XUnit2): The VSTest --filter syntax is identical on both VSTest and MTP. No changes needed.

xUnit.net v3 (native MTP): xUnit.net v3 does NOT support the VSTest --filter syntax on MTP. Translate filters using xUnit.net v3's native options:

VSTest `--filter` syntax	xUnit.net v3 MTP equivalent	Notes
`FullyQualifiedName~ClassName`	`--filter-class ClassName`	Wildcards required for substring match
`FullyQualifiedName=Ns.Class.Method`	`--filter-method Ns.Class.Method`	Exact match on fully qualified method
`Name=MethodName`	`--filter-method MethodName`	Wildcards for substring match
`Category=Value` (trait)	`--filter-trait "Category=Value"`	Filter by trait name/value pair
Complex expressions	`--filter-query "expr"`	Uses xUnit.net query filter language (see above)

Files

ATTRIBUTION.mdAdded by AutoGineer837 B
LICENSELicence file added by AutoGineer1.1 KiB
SKILL.md5.8 KiB

Requirements and compatibility

Written for: Claude Code

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Needs: Claude Code frontmatter

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Download ZIP

The ZIP holds the skill’s files, its licence files and an ATTRIBUTION.md. Download filter-syntax.zip