running-unit-tests

# Running MSBuild Unit Tests This repo uses **xUnit v3** with the **Microsoft.Testing.Platform (MTP)** runner. Test projects are built as `OutputType=Exe`, so each test assembly is a self-contained host process — *not* a classic VSTest assembly. There are **two ways to run tests**: | Method | When to use | |--------|-------------| | `dotnet test <project>` | Dev loop — run a single test project, optionally filtered | | `build.cmd -test` / `build.sh --test` | Final validation — builds everything and runs all test projects via the repo's Arcade harness | Use a **fast, scoped** `dotnet test` loop while iterating, and the **full `build.cmd -test`** pass before declaring the change done. ## Repo-specific knobs to know about These are configured in `Directory.Build.props` (repo root), `src/Directory.Build.targets`, and `src/Shared/UnitTests/xunit.runner.json`. They apply to both `dotnet test` and `build.cmd -test` unless noted otherwise: - **Multi-targeting**: test projects target .NETFramework and .NETCoreApp on Windows (.NETCoreApp only on Linux/macOS). `dotnet test` runs the suite **once per TFM**. - **Single-threaded by default**: `xunit.runner.json` sets `maxParallelThreads: 1` and `parallelizeTestCollections: false`. Many tests mutate process-global state (env vars, cwd, SDK resolvers), so this is intentional. - **Auto trait filters**: platform/TFM-inappropriate tests are filtered out via `--filter-not-trait Category=...` (e.g., `nonwindowstests`, `failing`, `nonnetcoreapptests`). Don't try to "fix" tests that appear skipped because of these. - **Coverage on non-Windows**: `--coverage --coverage-settings Coverage.config` is appended unconditionally to `XunitOptions` in `src/Directory.Build.targets`. There is no MSBuild property switch to disable it from `dotnet test` — to skip coverage, run the test exe directly without `--coverage`. - **Test runner**: `TestRunnerName=XUnitV3`, MTP `1.9.1`, xUnit v3 `3.2.2` (set in repo-root `Directory.Build.props`). - **DOTNET_HOST_PATH**: `RunnerUtilities.GetMSBuildEnvironmentVariables` (in `src/UnitTests.Shared/RunnerUtilities.cs`) sets `DOTNET_HOST_PATH` to the bootstrap dotnet when tests launch MSBuild as a child process, so tasks like `RoslynCodeTaskFactory` resolve the right host. Don't override `DOTNET_HOST_PATH` from a test. ## Flags — MTP vs VSTest pitfalls This repo uses MTP with the xUnit v3 MTP runner, **not** VSTest. Many familiar `dotnet test` flags silently do nothing. Key differences: - **Use** `--report-trx` (not `--logger trx`), `--coverage` (not `--collect "XPlat Code Coverage"`), `--filter-method`/`--filter-class`/`--filter-trait` for xUnit v3 native filtering. - **Don't use** `--filter`, `--nologo`, `--blame`, `--settings *.runsettings`, `--diag`, `--collect`, or `-- RunConfiguration.MaxCpuCount=...` — these are VSTest-only and ignored. - **Still works**: `-c`, `-f`, `--no-restore`, `--no-build`, `-v`, `-bl:`, `-p:Property=Value` — these are interpreted by `dotnet test` itself before MTP sees them. For comprehensive MTP vs VSTest flag reference, see the `run-tests` skill from the `dotnet-test` plugin. ## Dev loop: fast and scoped Aim for sub-30s iterations. > Examples below use Windows-style backslashes and PowerShell line continuations. Forward slashes work everywhere with `dotnet` (`src/Tasks.UnitTests/Microsoft.Build.Tasks.UnitTests.csproj`); on Linux/macOS use `/` and shell line continuations (`\`), and the exe path becomes `artifacts/bin/<Proj>/Debug/net11.0/<Proj>` (no `.exe`). 1. **Run via `dotnet test` with a single TFM and filter** (incremental build handles rebuilding automatically): ```powershell dotnet test src\Tasks.UnitTests\Microsoft.Build.Tasks.UnitTests.csproj ` -f net11.0 -- --filter-method "*MyFeature*" ``` 2. **Or run the test exe directly** (fastest — no SDK overhead; build first if source changed): ```powershell dotnet build src\Tasks.UnitTests\Microsoft.Build.Tasks.UnitTests.csproj -c Debug -f net11.0 artifacts\bin\Microsoft.Build.Tasks.UnitTests\Debug\net11.0\Microsoft.Build.Tasks.UnitTests.exe ` --filter-method "*MyFeature*" --no-progress ``` The exe path is TFM-specific: `Debug\net11.0\...exe` for net11.0, `Debug\net472\...exe` for net472. Switching TFM without rebuilding silently runs stale binaries. ### Speeding up the dev loop further These trade safety for speed — use during iteration, **revert before final validation**: -- **Single TFM**: pass `-f net11.0`. Halves runtime on Windows by skipping `net472`. - **Temporarily relax single-threaded execution**: drop a `xunit.runner.json` next to the test project (or override the existing one) with: ```json { "$schema": "https://xunit.net/schema/current/xunit.runner.schema.json", "longRunningTestSeconds": 60, "maxParallelThreads": -1, "parallelizeTestCollections": true } ``` Or pass them as runner args after `--`: `-- xUnit.MaxParallelThreads=-1 xUnit.ParallelizeTestCollections=true`. Expect flakes in tests that touch env vars, cwd, the file system, or the global ProjectCollection — **don't ship a fix that depends on this being on**. - **Skip bootstrap packaging** for non-bootstrap test projects: `dotnet build ... -p:CreateBootstrap=false` (useful when the local bootstrap SDK payload is missing). - **Narrow with traits**: `--filter-trait Category=mytraitduringdev` if you've tagged a focused subset. - **Skip code coverage on Linux/macOS**: run the test exe directly without `--coverage`. This repo does not expose a supported `dotnet test` property switch to disable the auto-added coverage arguments. ## Final validation pass Before saying "done," run the heavy configuration. Don't skip TFMs and don't keep parallel-overrides. 1. **Restore parallelism settings** (revert any local `xunit.runner.json` change). 2. **Run all TFMs for affected projects**: ```powershell dotnet test src\Build.UnitTests\Microsoft.Build.Engine.UnitTests.csproj -c Release dotnet test src\Tasks.UnitTests\Microsoft.Build.Tasks.UnitTests.csproj -c Release # Add other UnitTests projects whose code paths you touched ``` 3. **For broad changes (engine, framework, shared)**, run the full repo test suite (~9 minutes — do not cancel): ```powershell .\build.cmd -test -c Release # Windows ./build.sh --test -c Release # Linux/macOS ``` 4. **Capture a TRX** if reporting results to the user or CI: ```powershell dotnet test <project> -c Release ` --report-trx --report-trx-filename validation.trx ` --results-directory artifacts\TestResults ``` ## Reading the summary line MTP's final summary reports `passed`, `failed`, and `skipped` separately. **Always check the `skipped` count** — platform-conditional attributes (`WindowsOnlyFact`, `UnixOnlyFact`, etc.) and the auto trait filters cause expected skips, but a sudden jump in skipped count can hide a regression where a test became inapplicable on the current platform without you intending it. ## Picking the right project to run Match the source area you changed to its `*.UnitTests` project: | Source area | Test project | |-------------|--------------| | `src/Build/**` (engine, evaluation, backend) | `src/Build.UnitTests/Microsoft.Build.Engine.UnitTests.csproj` | | `src/Framework/**` | `src/Framework.UnitTests/Microsoft.Build.Framework.UnitTests.csproj` | | `src/Tasks/**` | `src/Tasks.UnitTests/Microsoft.Build.Tasks.UnitTests.csproj` | | `src/Utilities/**` | `src/Utilities.UnitTests/Microsoft.Build.Utilities.UnitTests.csproj` | | `src/MSBuild/**` (CLI) | `src/MSBuild.UnitTests/Microsoft.Build.CommandLine.UnitTests.csproj` | | `src/Build/BuildCheck/**` | `src/BuildCheck.UnitTests/Microsoft.Build.BuildCheck.UnitTests.csproj` | | `src/Shared/**` | Run the consumers above (Build, Tasks, Utilities) — shared code is linked into all of them. | ## Quick reference | Scenario | Command | |----------|---------| | Fast scoped dev loop | `dotnet test <proj> -f net11.0 -- --filter-method "*X*"` | | Direct test exe | `artifacts\bin\<Proj>\Debug\net11.0\<Proj>.exe --filter-method "*X*" --no-progress` | | Single test by name | `dotnet test <proj> -- --filter-method "*MyTestMethod*"` | | Final per-project validation | `dotnet test <proj> -c Release` (all TFMs) | | Final full validation | `.\build.cmd -test -c Release` / `./build.sh --test -c Release` | | TRX report | `--report-trx --report-trx-filename out.trx --results-directory artifacts\TestResults` | ## See also - `.github/instructions/tests.instructions.md` — test authoring conventions (xUnit v3, Shouldly, `TestEnvironment`, `MockLogger`). - `src/Shared/UnitTests/xunit.runner.json` — repo-wide xUnit settings. - `src/Directory.Build.targets` — `XunitOptions`, auto trait filters, coverage wiring. - `documentation/wiki/Building-Testing-and-Debugging-on-Full-Framework-MSBuild.md`