# Build And Test > Build and test dotnet/runtime locally. Covers the mandatory baseline build, per-component build and test commands, Windows/PowerShell equivalents, running individual tests, and troubleshooting. USE FOR: any build or test invocation in this repo, and before making code changes under CCA. DO NOT USE FOR: CI pipeline triage (use ci-pipeline-monitor) or benchmarking (use performance-benchmark). - Skill: `dotnet/build-and-test` (Agent Skill, multi-file: 5 files) - Install (CLI): `npx skillmds@latest add dotnet/build-and-test` - Raw SKILL.md: https://api.skillmd.com/api/skills/dotnet/build-and-test/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Web & Frontend - Author: .NET (Microsoft) (https://skillmd.com/u/dotnet) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/dotnet/build-and-test --- # Building & Testing in dotnet/runtime ## Shell Conventions Commands below are written for bash. On Windows, use the `.cmd` entrypoints and PowerShell equivalents: | bash | Windows (PowerShell) | |------|----------------------| | `./build.sh ` | `.\build.cmd ` | | `src/tests/build.sh ` | `src\tests\build.cmd ` | | `src/tests/run.sh ` | `src\tests\run.cmd ` | | `export FOO=` | `$env:FOO = ''` | | `$CORE_ROOT/corerun .dll` | `& "$env:CORE_ROOT\corerun.exe" .dll` | | `find -name ''` | `Get-ChildItem -Recurse -Filter ''` | | `tail -20 ` | `Get-Content -Tail 20` | | `grep '' ` | `Select-String -Path -Pattern ''` | Some arguments also differ in casing: `-priority1` on bash is `-Priority 1` on Windows. ## Baseline Build A successful baseline build of the affected component is required for incremental builds and tests. Without it you'll hit "missing testhost" and "shared framework" errors that cost 20+ minutes per occurrence. If a baseline build fails, STOP, report the failure, and do not attempt to work around it. ### When a baseline is required - **Under CCA — always, before changing any of the product code in the table below.** ⚠️ The environment is fresh, so there are no pre-existing artifacts and incremental builds fail in ways that waste significant compute. Skipping this step IS a task failure. Changes outside those paths — docs, markdown, workflow and instruction files — don't need one. **Exception:** if you are on a feature branch with commits upstream of main and the baseline build fails, make whatever code changes are needed to fix the build, then resume requiring a baseline. - **Under CLI (interactive) — only when needed.** A usable baseline may already exist from prior work; don't re-run a 40-minute build unnecessarily. Check the component's [baseline sentinel](#baseline-sentinels) and build if it is missing. Otherwise attempt the work, and if it fails with a baseline-missing signature from [Troubleshooting](#troubleshooting), run the baseline once and retry — do not loop. Trust volunteered user signals ("just built", "fresh checkout") over probing. - **Unsure which mode you're in?** Follow the CCA rule. ### Step 1: Build the Baseline (from repo root) Pick the row matching the files you will modify: | Files Changed | Component | Baseline Build | |---------------|-----------|----------------| | `src/coreclr/` | CoreCLR | `./build.sh clr+libs+host` | | `src/mono/` | Mono | `./build.sh mono+libs` | | `src/libraries/` (no Browser/WASM or WASI targets) | Libraries | `./build.sh clr+libs -rc release` | | `src/libraries/` with Browser/WASM or WASI targets in the affected `.csproj` | WASM/WASI Libraries | `./build.sh mono+libs -os browser` | | `src/native/corehost/`, `src/installer/` | Host | `./build.sh clr+libs+host -rc release -lc release` | | `src/tools`, `src/native/managed` | Tools | `./build.sh clr+libs -rc release` | | `src/tasks` | Build Tasks | None — `./build.sh tasks` is self-contained | | `src/tests` | Runtime Tests | `./build.sh clr+libs -lc release -rc checked` | **WASM/WASI Library Detection:** A change under `src/libraries/` is WASM/WASI-relevant if the library's `.csproj` has explicit Browser/WASM or WASI targets (`TargetFrameworks`, `TARGET_BROWSER`, `TARGET_WASI` constants, or `Condition` attributes referencing `browser`/`wasi`), **and** the changed file is not excluded from those targets via `Condition` on `` or ``. For System.Private.CoreLib changes, use `-rc checked` instead of `-rc release` for asserts. Build on the branch you intend to modify — the baseline reflects your working tree at that moment. Baselining up front requires a clean HEAD; baselining after a probe failure means either stashing work-in-progress changes first or accepting that the baseline incorporates them. ⏱️ **This build can take up to 40 minutes.** Do not cancel unless no output for 5+ minutes. Redirect it to a log and poll a bounded view rather than watching the console: ```bash ./build.sh clr+libs -rc release > artifacts/build.log 2>&1; echo "exit=$?" > artifacts/build.status ``` Then check `artifacts/build.status`, `tail -20 artifacts/build.log`, or grep the log for `: error`. `artifacts/log/` holds the per-project binlogs for reporting failures. ### Baseline sentinels A path under `artifacts/` whose absence means the baseline is missing. | Component | Sentinel | |-----------|----------| | Libraries | `artifacts/bin/testhost/` and `artifacts/bin/microsoft.netcore.app.runtime.//`. Building a single library usually works without one; running its tests does not. | | CoreCLR | `artifacts/bin/coreclr/../`, plus `artifacts/tests/coreclr/../Tests/Core_Root/` to run tests | | Mono | `artifacts/bin/mono/../`, plus `artifacts/tests/coreclr/../Tests/Core_Root/` to run tests (Mono reuses the Core_Root layout) | | WASM Libraries | `artifacts/bin/microsoft.netcore.app.runtime.browser-wasm//` | | Host | `artifacts/bin/coreclr/../` and `artifacts/bin/testhost/` | | Tools | `artifacts/bin/coreclr/../` and `artifacts/bin/testhost/` | | Build Tasks | None — `./build.sh tasks` is self-contained | | Runtime Tests | `artifacts/tests/coreclr/../Tests/Core_Root/`, produced by the baseline build plus `src/tests/build.sh -GenerateLayoutOnly` | ### Step 2: Configure Environment ```bash export PATH="$(pwd)/.dotnet:$PATH" dotnet --version # Should match sdk.version in global.json ``` On Windows: `$env:PATH = "$PWD\.dotnet;$env:PATH"` --- ## Component Workflows Read only the file for the component you are working on. All commands must complete with exit code 0, and all tests must pass with zero failures. | Component | Workflow | |-----------|----------| | Libraries, WASM/WASI Libraries | [`components/libraries.md`](components/libraries.md) | | CoreCLR, Mono | [`components/runtime.md`](components/runtime.md) | | Runtime Tests (`src/tests`) | [`components/runtime-tests.md`](components/runtime-tests.md) | | Host, Tools, Build Tasks | [`components/host-and-tools.md`](components/host-and-tools.md) | --- ## Adding new tests When creating a regression test for a bug fix: 1. **Verify the test FAILS without the fix** — build and run against the unfixed code. 2. **Verify the test PASSES with the fix** — apply the fix, rebuild, and run again. 3. If the fix is not yet merged locally, manually apply the minimal changes from the PR/commit to verify. Do not mark a regression test task as complete until both conditions are confirmed. ## Troubleshooting | Error | Solution | |-------|----------| | "shared framework must be built" | Run baseline build: `./build.sh clr+libs -rc release` | | "testhost" missing / FileNotFoundException | Run baseline build first (Step 1 above) | | Build timeout | Wait up to 40 min; only fail if no output for 5 min | | "Target does not exist" | Avoid specifying a target framework; the build will auto-select `$(NetCoreAppCurrent)` | | "0 test projects" after `build.sh -Test` | The test has `` > 0; add `-priority1` to the build command | **When reporting failures:** Include logs from `artifacts/log/` and console output for diagnostics.