Incremental Test (.NET)

---
name: incremental-test
description: >-
  Run dotnet.Tests incrementally without a full build.cmd rebuild. Use after
  modifying source code in SDK projects to quickly build only changed projects,
  deploy their outputs into the redist SDK layout, and run tests against them.
metadata:
  origin: .NET
---

# Incremental Test Runner for dotnet.Tests

## Prerequisites

- A full build must have been completed at least once (via `build.cmd` or `build.sh`) so that the redist SDK layout exists at `artifacts\bin\redist\Debug\dotnet\sdk\<version>\`.
- The repo-local `.dotnet` SDK must match the version expected by the test projects. If the runtime or SDK version is out of date (e.g., test build fails with a missing framework error), run `.\restore.cmd` (or `./restore.sh` on macOS/Linux) to download the correct SDK into `.dotnet`.
- This workflow uses Windows/PowerShell commands and paths. On macOS/Linux, substitute forward slashes and use `cp` instead of `Copy-Item`.

## Workflow

### Step 1: Identify modified projects

Determine which projects have been modified. Use context from:
- The files you just edited in this session.
- Or `git status`/`git diff` to find changed `.cs` files and map them to their `.csproj` projects.

### Step 2: Build modified projects

Build each modified project individually using the repo-local dotnet:

```
.\.dotnet\dotnet build <path-to-project.csproj> -c Debug
```

For example:
```
.\.dotnet\dotnet build src\Cli\Microsoft.DotNet.Cli.Utils\Microsoft.DotNet.Cli.Utils.csproj -c Debug
```

If the `dotnet` CLI project itself was modified, build it:
```
.\.dotnet\dotnet build src\Cli\dotnet\dotnet.csproj -c Debug
```

### Step 3: Copy output DLLs to the redist SDK layout

Discover the SDK version directory name:
```powershell
$sdkVersion = (Get-ChildItem artifacts\bin\redist\Debug\dotnet\sdk -Directory | Sort-Object LastWriteTime -Descending | Select-Object -First 1).Name
```

For each modified project, copy its output DLL (and any satellite assemblies) from the project's build output to the redist SDK directory:

```
Source: artifacts\bin\<ProjectName>\Debug\net10.0\<AssemblyName>.dll
Target: artifacts\bin\redist\Debug\dotnet\sdk\<version>\
```

For example:
```powershell
Copy-Item artifacts\bin\Microsoft.DotNet.ProjectTools\Debug\net10.0\Microsoft.DotNet.ProjectTools.dll artifacts\bin\redist\Debug\dotnet\sdk\$sdkVersion\
Copy-Item artifacts\bin\Microsoft.DotNet.Cli.Utils\Debug\net10.0\Microsoft.DotNet.Cli.Utils.dll artifacts\bin\redist\Debug\dotnet\sdk\$sdkVersion\
```

The `dotnet` project is special — it builds into `artifacts\bin\dotnet\Debug\net10.0\` and its `dotnet.dll` must be copied to the SDK directory:
```powershell
Copy-Item artifacts\bin\dotnet\Debug\net10.0\dotnet.dll artifacts\bin\redist\Debug\dotnet\sdk\$sdkVersion\
```

**Important notes:**
- For typical incremental edits, only copy DLLs that are **already present** in the target directory. If your change introduces a new shipped assembly or moves assemblies, you will need a full `build.cmd`/`build.sh` to update the layout correctly.
- Some projects multi-target (e.g., `net10.0` and `net472`). Always use the `net10.0` output.
- If localization resource DLLs were changed (in subdirectories like `cs\`, `de\`, etc.), copy those too.

### Step 4: Run the tests

Invoke the [`run-tests`](../run-tests/SKILL.md) skill for `test/dotnet.Tests/dotnet.Tests.csproj` with a filter for
the affected tests. It builds the test project incrementally and retains detailed output,
a TRX, and a binlog.

## Common project paths

| Assembly | Project Path |
|---|---|
| `dotnet.dll` | `src\Cli\dotnet\dotnet.csproj` |
| `Microsoft.DotNet.Cli.Utils.dll` | `src\Cli\Microsoft.DotNet.Cli.Utils\Microsoft.DotNet.Cli.Utils.csproj` |
| `Microsoft.DotNet.Cli.Definitions.dll` | `src\Cli\Microsoft.DotNet.Cli.Definitions\Microsoft.DotNet.Cli.Definitions.csproj` |
| `Microsoft.DotNet.Cli.CoreUtils.dll` | `src\Cli\Microsoft.DotNet.Cli.CoreUtils\Microsoft.DotNet.Cli.CoreUtils.csproj` |
| `Microsoft.DotNet.Configurer.dll` | `src\Cli\Microsoft.DotNet.Configurer\Microsoft.DotNet.Configurer.csproj` |
| `Microsoft.DotNet.ProjectTools.dll` | `src\Microsoft.DotNet.ProjectTools\Microsoft.DotNet.ProjectTools.csproj` |
| `Microsoft.DotNet.NativeWrapper.dll` | `src\Resolvers\Microsoft.DotNet.NativeWrapper\Microsoft.DotNet.NativeWrapper.csproj` |
| `Microsoft.DotNet.TemplateLocator.dll` | `src\Microsoft.DotNet.TemplateLocator\Microsoft.DotNet.TemplateLocator.csproj` |
| `Microsoft.DotNet.InternalAbstractions.dll` | `src\Cli\Microsoft.DotNet.InternalAbstractions\Microsoft.DotNet.InternalAbstractions.csproj` |
| `dotnet.Tests.dll` | `test\dotnet.Tests\dotnet.Tests.csproj` |