Setup test infrastructure

.NET Integration Test Infrastructure Setup

You are configuring container-based infrastructure for a .NET integration test project. Your job is to detect which services the source project depends on, then generate either Testcontainers C# fixture classes or a docker-compose.yml — whichever is appropriate.

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Step 1 — Locate the Source Project

Ask the user for the path to their source project's .csproj file (the project under test, not the test project itself). If the conversation already makes the path obvious (e.g. the user just showed you a file from it), use that path without asking.

Read the .csproj file and extract every <PackageReference Include="..."> entry.

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Step 2 — Detect Required Services

Compare each package name against the lookup table in references/package-service-map.md. Match using contains — a .csproj package name matches a table row if the package name contains the pattern string (case-insensitive).

For each matched package, record:

• The service name (e.g. PostgreSQL, Redis)
• The Docker image to use
• The Testcontainers NuGet package (e.g. Testcontainers.PostgreSql)
• The Testcontainers builder class (e.g. PostgreSqlBuilder)

If no packages match any row in the table, tell the user:

"I didn't detect any known service dependencies in your .csproj. If your project connects to a service not listed here, let me know which one and I'll generate the configuration manually."

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Step 3 — Choose an Approach

Scan the same .csproj for any <PackageReference> whose Include value starts with Testcontainers..

• If one or more Testcontainers.* packages are already referenced — use the Testcontainers approach (Step 4A).
• If no Testcontainers.* packages are referenced — use the docker-compose approach (Step 4B).

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Step 4A — Testcontainers Approach

Generate a C# fixture class for each detected service.

Follow the patterns in references/testcontainers-patterns.md precisely:

• Each fixture implements IAsyncLifetime.
• Containers start in InitializeAsync and are disposed in DisposeAsync.
• When there are multiple services, start them in parallel with Task.WhenAll inside a single combined fixture.
• Expose a GetConnectionString() (or equivalent) property so test classes can consume it without touching the container directly.
• Show the user how to inject the runtime connection string into WebApplicationFactory using the override pattern from the patterns reference.
• Include a IntegrationTestBase base class so individual test fixtures inherit lifecycle management without re-declaring it.

After generating the code, tell the user which NuGet packages to add to their test project:

dotnet add package Testcontainers.<Service> --version <latest>

List one command per detected service.

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Step 4B — Docker Compose Approach

Generate a single docker-compose.yml file containing a service block for each detected dependency.

Use the snippets from references/docker-compose-templates.md:

• Start with the standard compose header from the templates reference.
• Append the service snippet for each detected service.
• Place the file at the root of the test project directory (ask the user for this path if you don't already have it).

After generating the file, also tell the user:

"If you'd prefer programmatic container management instead of docker-compose, add these NuGet packages to your test project and re-run this skill:"

List the Testcontainers NuGet package for each detected service, one per line.

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Step 5 — Confirm Output

After generating files, summarize what was created:

• List each file path written
• List each service detected and the approach used for it
• State any services that were detected but are not in the package map (so the user knows they need manual configuration)

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Notes

• Always use the test project directory as the output location for generated files, not the source project directory.
• Do not modify the source project's .csproj — only read it.
• If the user is running this as part of a larger scaffolding workflow (invoked from scaffold-integration-project), skip asking for paths — they will be provided as arguments in the invocation context.
• Prefer Alpine-based images where available — they are significantly smaller and faster to pull in CI.

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Using This Skill From Other Skills

When another skill needs to set up test infrastructure as part of a larger workflow, add this to the calling skill's SKILL.md:

**REQUIRED SUB-SKILL:** Invoke `setup-test-infrastructure` with args:
`"source csproj: <path-to-source.csproj>, test project dir: <path-to-test-project/>"`

The generated fixture files and/or docker-compose.yml will be available for subsequent steps.