Clarify ClassDataSource constructor requirements

[thomhurst]

Summary

• Document the accessible parameterless constructor requirement for ClassDataSource<T> types.
• Distinguish supported test-class constructor injection from unsupported constructor injection inside data source types.
• Add a nested property-injection example and cross-reference the detailed guide.

Validation

• yarn build from docs

Refs #6694

Summary by CodeRabbit

• Documentation
  • Clarified that ClassDataSource<T> types require a public parameterless constructor.
  • Recommended property injection for nested dependencies within data sources.
  • Added guidance and an example for asynchronously initializing dependent fixtures.
  • Documented that constructor-injected dependencies inside data source types are not currently supported.
  • Updated shared-fixture guidance to clarify test-class constructor parameter usage.

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Greptile Summary

The PR clarifies the construction rules for ClassDataSource<T> and distinguishes test-class constructor injection from nested data-source dependency injection.

• States consistently that data-source types require a public parameterless constructor.
• Recommends property injection for nested dependencies.
• Adds an initialization-order example and links to the detailed nested-property-injection guide.

Confidence Score: 5/5

The documentation-only PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
README.md	Clarifies that constructor parameters are supported on test classes while data-source types require public parameterless constructors.
docs/docs/writing-tests/class-data-source.md	Documents the public-constructor requirement and adds a nested property-injection example with lifecycle guidance.
docs/docs/writing-tests/nested-data-sources.md	Explicitly directs nested data-source dependencies to property injection and accurately states the public-constructor requirement.

_{Reviews (2): Last reviewed commit: "docs: require public ClassDataSource con..." | Re-trigger Greptile}

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Team

Run ID: 01526aa2-a1be-41e1-8633-e342a6a85327

📥 Commits

Reviewing files that changed from the base of the PR and between 8685475 and 2d22632.

📒 Files selected for processing (3)

• README.md
• docs/docs/writing-tests/class-data-source.md
• docs/docs/writing-tests/nested-data-sources.md

🚧 Files skipped from review as they are similar to previous changes (3)

• README.md
• docs/docs/writing-tests/nested-data-sources.md
• docs/docs/writing-tests/class-data-source.md

Included review availability: Your plan provides up to 8 included reviews per hour; 2 remain after this review.

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📝 Walkthrough

Walkthrough

The documentation states that ClassDataSource<T> requires a public parameterless constructor. It recommends property injection for nested dependencies and documents constructor injection on the receiving test class.

Changes

ClassDataSource documentation

Layer / File(s)	Summary
Constructor and nested dependency guidance docs/docs/writing-tests/class-data-source.md, docs/docs/writing-tests/nested-data-sources.md, README.md	The documentation explains ClassDataSource<T> constructor requirements, distinguishes test-class constructor injection from data-source construction, and provides an IAsyncInitializer example using property injection for nested dependencies.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Merge Risk: ⚪ Minimal · up to 2d226

This documentation update clarifies supported dependency injection patterns for ClassDataSource types, with no identified merge-readiness risk.

Poem

A rabbit reads the fixture guide,
With nested properties safe inside.
A public constructor marks the way,
While async fixtures start the day.
Clear documentation leads the way.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: documenting the constructor requirements for ClassDataSource types.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (3 skipped: 3 unsupported.)

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch docs/class-data-source-constructor-requirements

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Code review

Reviewed the diff (README.md, docs/docs/writing-tests/class-data-source.md, docs/docs/writing-tests/nested-data-sources.md) — this is a documentation-only change with no source-gen or reflection-engine code touched, so the dual-mode requirement in CLAUDE.md doesn't apply here.

Technical accuracy check: I verified the core claim against the implementation rather than taking it on faith. ClassDataSources.Create (src/TUnit.Core/Attributes/TestData/ClassDataSources.cs:92) instantiates data-source types via Activator.CreateInstance(type) with no constructor arguments — which does require a public parameterless constructor. The new docs and example (nested ApplicationFixture/DatabaseFixture using property injection + IAsyncInitializer) accurately reflect this behavior and the initialization order described in nested-data-sources.md.

No issues found. The added example is clear, the distinction between test-class constructor injection (supported) and data-source constructor injection (unsupported) is well explained, and no CLAUDE.md rules are implicated by a docs-only change. Nothing to flag architecturally — this is straightforward prose/example documentation, not a case where alternative designs apply.

🤖 Generated with automated code review