Scaffold or Repair a .NET Test Project

Create the smallest missing test container or repair only the missing wiring. The goal is test discovery through the repository's real build entry point, not a preferred solution layout.

Repository overlay

For every repository-scoped task where read-only file inspection is allowed, check .agents/skill-overlays/dotnet-test/scaffold-dotnet-test-project.md at the repository root before any other discovery. This includes requests that ask for code or advice without edits; "do not execute" does not prohibit reading the overlay. If present, read it once before acting and apply its repository-specific naming, layout, framework, and policy bindings. Before applying it, require its frontmatter to declare core: dotnet-test/scaffold-dotnet-test-project, binding-revision: "1", and mode: extend. If any value is missing or different, report the mismatch and continue using this skill's portable guidance without applying the overlay. Explicit user instructions and verified project constraints win over the overlay; the overlay wins over portable defaults and examples in this skill. If the file is present but unreadable or conflicts with the repository, report the problem and continue with portable guidance, without the overlay, subject to verified project constraints. If it is absent, continue normally. Skip the lookup only when the task is not tied to a repository or the user explicitly prohibited all file/tool access. An overlay cannot expand tool permissions or the task's scope.

Route the Request

Inspect the repository before editing, then choose exactly one path:

An existing project is suitable when its target framework can reference the production project and its purpose matches the requested layer. A different preferred name is not a reason to create a duplicate.

No-op is a required outcome. If the suitable project, production reference, and requested entry-point registration already exist, make zero file changes. Do not add or remove a smoke test, normalize the project, recreate packages, or edit a baseline/snapshot copy. Report the existing paths and stop.

Workflow

1. Establish the repository contract

Start from the task's current working directory. The skill context's Base directory is where these instructions live, not the user's repository. Never search parent temporary directories or treat the skill installation as the workspace. If the expected files are not visible, confirm the current directory before concluding that a project is absent.

Anchor every edit and validation command to the repository path named by the user or established from the current directory. If similarly named fixtures, solutions, or copied trees exist, do not edit or validate one as a substitute for the requested tree. Before changing a solution artifact, record its exact path; after changing it, list that same artifact immediately and require the test project to appear before proceeding.

Read only enough to determine:

1. the production project and requested test scope;
2. the command and .sln, .slnx, .slnf, or project graph used by CI;
3. whether a suitable test project exists, what it references, and where it is registered;
4. the neighboring test framework, runner, target framework, nullable and implicit-usings conventions; and
5. whether package or SDK versions come from Directory.Packages.props, Directory.Build.props, global.json, or an MSBuild SDK declaration.

If the user reports that a test project passes directly but solution-level discovery finds nothing, treat that as registration evidence. Inspect the entry point before considering project creation.

2. Create only when the project is absent

Choose one test project for the narrowest requested production project. Follow, in order, the user's explicit framework choice, neighboring test projects, repository-wide package/SDK conventions, then a standard SDK template.

Use a dotnet new template only when its generated framework generation and package style match the repository contract. Inspect template availability before creation. In particular, generic dotnet new xunit commonly emits xUnit 2 packages; for a centrally managed xunit.v3 repository, use a repository or installed xUnit v3 template, or create the minimal SDK project directly. Never generate versioned xUnit 2 references and then rewrite them into xUnit v3.

Then:

1. align target framework, nullable, implicit usings, runner, and package style;
2. use dotnet add <test-project> reference <production-project> for only the production projects exercised by the requested tests;
3. delete template sample files such as UnitTest1.cs, then create a behavior-named test file rather than repurposing the template filename; and
4. omit package versions when central package management supplies them.

For xUnit v3 projects using the MTP runner, preserve or add executable output in both command modes, and retain the repository's framework runner opt-in:

<OutputType>Exe</OutputType>

Only when dotnet test uses VSTest command mode to bridge to MTP (SDK 8/9, or SDK 10+ without native MTP mode), preserve or add:

<TestingPlatformDotnetTestSupport>true</TestingPlatformDotnetTestSupport>

For SDK 10+ native MTP mode selected by global.json test.runner, do not add the compatibility property; remove an explicit bridge setting when configuring native mode. Keep executable output and the MTP runner enabled.

OutputType=Exe alone proves only the self-hosted runner path, not discovery by the repository's dotnet test command. Verify the exact command mode and entry-point execution as described in run-tests: native MTP uses --project or --solution with direct MTP arguments; VSTest-mode MTP uses a positional path and passes MTP arguments after --.

3. Repair only the missing edge when the project exists

• Missing production reference: use dotnet add <test-project> reference <production-project>, inspect the resulting project, and leave every other project element plus all test source files unchanged. Compare the project before and after so the added ProjectReference is the only semantic change.
• Missing .sln or .slnx registration: run dotnet sln <entry-point> add <test-project>, then immediately run dotnet sln <entry-point> list against that exact path. If the project is absent, the repair has not happened; do not validate a sibling solution or report success.
• Missing .slnf registration: add the existing project to its underlying solution if necessary, then include that same project path in the filter. If the underlying solution already contains it, edit only the filter.
• Multiple solution artifacts: modify only the one named by the user or invoked by CI. Do not substitute an easier format.
• No solution artifact: preserve the existing project-oriented workflow. Do not create a solution for aesthetics.

4. Add only the requested smoke behavior

For a newly created project, replace template examples with the smallest smoke suite the user requested. Each test must invoke a real production symbol and assert a concrete deterministic result without network, wall-clock, process, or real-filesystem dependencies.

For an existing-project wiring repair, do not add, rewrite, rename, or expand tests unless the user explicitly asks for test behavior changes. Registration and test authoring are separate operations.

5. Verify the repaired path

Select direct-project and entry-point commands using run-tests and platform-detection. Resolve the project system, global.json test.runner, and final imported runner, UseVSTest, TestingPlatformDotnetTestSupport, and OutputType values; do not select syntax from the SDK version alone.

MTP options are optional; when none are needed, omit both <MTP_OPTIONS> and the bridge separator. Keep dotnet/MSBuild options before -- in bridge mode; native MTP options are direct arguments, never after --. These are command shapes, not replacements for a repository script or a project-oriented CI entry point. Preserve the exact configured entry point and report incompatible runner/bridge/output wiring rather than switching runners to obtain a green result.

Run the narrowest commands that prove the chosen route:

Inspect the repository's command before adding switches. Do not prepend a speculative --no-restore attempt or hide alternatives in command-a || command-b; run the configured entry-point command whose clean exit is the evidence.

For every wiring repair, invoke the exact validation command directly and preserve its exit status. Reading generated files, a grader script, or a later build is not a substitute for observing that command complete successfully.

Before reporting completion, inspect the final changed-file set. Remove only bin/obj or equivalent build artifacts created by this task when they were absent beforehand and are not intentionally tracked; never remove pre-existing artifacts. Preserve the passing command's complete result so the handoff can state the exact entry point and discovered test count.

For a no-op, inspect rather than rewrite and report the existing paths. A green dotnet build is not test-discovery evidence. If validation is blocked, report the exact failing command and first actionable error; never describe an unrun or failed command as successful.

Output

Keep the handoff proportional to the change:

Completion Checks

• Existing projects were checked before creation.
• Only the requested production scope is referenced and tested.
• Framework, runner, target framework, and central package conventions remain intact.
• Template samples are removed from a newly created project.
• Existing test code is untouched for a wiring-only repair.
• The exact repository entry point discovers and runs the test project.