TUnit

Trigger On

• the repo uses TUnit
• you need to add, run, debug, or repair TUnit tests
• the repo uses Microsoft.Testing.Platform-based test execution
• the repo uses ClassDataSource<...>(Shared = SharedType.PerTestSession), ParallelLimiter, TUnit.Playwright, or --treenode-filter

Value

• produce a concrete project delta: code, docs, config, tests, CI, or review artifact
• reduce ambiguity through explicit planning, verification, and final validation skills
• leave reusable project context so future tasks are faster and safer

Do Not Use For

• xUnit projects
• MSTest projects
• generic test strategy with no TUnit-specific mechanics

Inputs

• the nearest AGENTS.md
• the test project file and package references
• the repo's current TUnit execution command

Quick Start

1. Read the nearest AGENTS.md and confirm scope and constraints.
2. Run this skill's Workflow through the Ralph Loop until outcomes are acceptable.
3. Return the Required Result Format with concrete artifacts and verification evidence.

Workflow

1. Confirm the project really uses TUnit and not a different MTP-based framework.
2. Read the repo's real test command from AGENTS.md. If the repo has no explicit command yet, start with dotnet test PROJECT_OR_SOLUTION.
3. Keep the TUnit execution model intact:

• tests are source-generated at build time
• tests run in parallel by default
• built-in analyzers should remain enabled

1. Choose the fixture level deliberately:

• plain TUnit tests for isolated logic
• shared AppHost/Aspire fixtures for HTTP, SignalR, SSE, or UI flows
• WebApplicationFactory layered over shared Aspire infra when tests need Host DI services, IGrainFactory, or other runtime internals

1. Reuse expensive fixtures with ClassDataSource<Fixture>(Shared = SharedType.PerTestSession) instead of booting distributed infrastructure per test.
2. Fix isolation bugs instead of globally serializing the suite unless the repo already documented a justified exception.
3. Run the narrowest useful scope first with dotnet test ... -- --treenode-filter "...". Keep TUnit arguments after --.
4. Capture useful failure evidence: host log dumps, focused console output, coverage files, and Playwright screenshots/HTML for UI tests.
5. Use [Test], [Arguments], hooks, and dependencies only when they make the scenario clearer, not because the framework allows it.

Bootstrap When Missing

If TUnit is requested but not configured yet:

1. Detect current state:

• rg -n "TUnit|Microsoft\\.Testing\\.Platform" -g '*.csproj' -g 'Directory.Build.*' .

1. Add the minimal package set to the test project:

• dotnet add TEST_PROJECT.csproj package TUnit
• add Microsoft.NET.Test.Sdk only when the repo's chosen TUnit project shape requires it; do not blindly duplicate runner packages

1. Keep the runner model explicit in AGENTS.md and CI:

• record that the repo uses Microsoft.Testing.Platform-compatible execution for this test project
• record the exact dotnet test TEST_PROJECT.csproj command the repo will use

1. Add one small executable test using [Test].
2. Run dotnet test TEST_PROJECT.csproj and return status: configured or status: improved.
3. If the repo intentionally standardizes on xUnit or MSTest, return status: not_applicable unless migration is explicitly requested.

Deliver

• TUnit tests that respect source generation and parallel execution
• commands that work in local and CI runs
• framework-specific verification guidance for the repo
• a fixture strategy that matches the actual test scope: logic-only, AppHost/API, Host DI/grains, or Playwright UI

Validate

• the command matches the repo's TUnit runner style
• focused runs use --treenode-filter rather than VSTest-style --filter
• shared distributed fixtures use SharedType.PerTestSession or an equivalent reuse pattern
• shared state is isolated or explicitly controlled
• built-in TUnit analyzers remain active
• coverage tooling matches Microsoft.Testing.Platform if coverage is enabled
• UI failures capture artifacts and server-side failures expose enough logs to avoid blind reruns

Test Harness

mermaid
flowchart LR
  A["TUnit task"] --> B{"What does the test need?"}
  B -->|"Single component only"| C["Plain TUnit test"]
  B -->|"HTTP / SignalR / resource graph"| D["Shared Aspire/AppHost fixture"]
  B -->|"Host DI / grains / runtime services"| E["Shared Aspire/AppHost fixture + WebApplicationFactory"]
  B -->|"Browser automation"| F["Shared Aspire/AppHost fixture + Playwright"]
  C & D & E & F --> G["Run focused with --treenode-filter"]
  G --> H["Capture logs, artifacts, and coverage"]

Ralph Loop

Use the Ralph Loop for every task, including docs, architecture, testing, and tooling work.

1. Plan first (mandatory):

• analyze current state
• define target outcome, constraints, and risks
• write a detailed execution plan
• list final validation skills to run at the end, with order and reason

1. Execute one planned step and produce a concrete delta.
2. Review the result and capture findings with actionable next fixes.
3. Apply fixes in small batches and rerun the relevant checks or review steps.
4. Update the plan after each iteration.
5. Repeat until outcomes are acceptable or only explicit exceptions remain.
6. If a dependency is missing, bootstrap it or return status: not_applicable with explicit reason and fallback path.

Required Result Format

• status: complete | clean | improved | configured | not_applicable | blocked
• plan: concise plan and current iteration step
• actions_taken: concrete changes made
• validation_skills: final skills run, or skipped with reasons
• verification: commands, checks, or review evidence summary
• remaining: top unresolved items or none

For setup-only requests with no execution, return status: configured and exact next commands.

Load References

• references/patterns.md
• references/migration.md
• references/tunit.md
• references/integration-testing.md

Running Tests

TUnit uses Microsoft.Testing.Platform. Use --treenode-filter for filtering (not --filter), and keep runner switches after --.

bash
# Run all tests
dotnet test MySolution.sln

# Run one test project
dotnet test tests/MyProject.Tests/MyProject.Tests.csproj

# Filter by class
dotnet test tests/MyProject.Tests/MyProject.Tests.csproj -- --treenode-filter "/*/*/CalculatorTests/*"

# Filter by category
dotnet test tests/MyProject.Tests/MyProject.Tests.csproj -- --treenode-filter "/*/*/*/*[Category=Integration]"

# Coverage on Microsoft.Testing.Platform
dotnet test MySolution.sln -- --coverage --coverage-output coverage.cobertura.xml --coverage-output-format cobertura

# Raw runner help when the repo needs direct TUnit app switches
dotnet run --project tests/MyProject.Tests/MyProject.Tests.csproj -- --help

Filter syntax: /<Assembly>/<Namespace>/<Class>/<Test> with * wildcards. See references/patterns.md for full examples.

Example Requests

• "Run this TUnit project correctly."
• "Fix our TUnit CI command."
• "Add a regression test in TUnit without breaking parallelism."