feat(aspnetcore): add PerTestWebApplicationTest with per-test CreateFactoryAsync

[thomhurst]

Summary

Addresses the per-test configuration request in discussion #7006.

WebApplicationTest<TFactory, TEntryPoint> configures the application through class-level overrides, so every test in a class gets the same configuration. Tests that need configuration only known in the test body (for example a fake that the test creates and asserts on afterwards) had to use one class per configuration, branch on TestContext inside the overrides, or build their own factory and lose TUnit's wiring.

• New PerTestWebApplicationTest<TFactory, TEntryPoint> holds the shared wiring (GlobalFactory, override methods, SetupAsync, ConfigureTestOptions, hooks) and adds protected CreateFactoryAsync(Action<IWebHostBuilder>? configure = null).
  • The delegate runs after ConfigureWebHostBuilder, ConfigureTestServices and ConfigureTestConfiguration, so it can replace anything the class configures.
  • Returned factories get the same isolation, logging, tracing and test context wiring as Factory, are built under the shared init semaphore, and are disposed after the test.
  • No application is built before the test; it has no Factory or Services property, so there is no member that throws when unused.
• WebApplicationTest<TFactory, TEntryPoint> now derives from it and keeps its eager Factory, Services and HttpCapture. Its tests can also call CreateFactoryAsync to build an extra application without replacing Factory.
• Docs: new "Per-Test Application Configuration" section and API reference row in docs/docs/examples/aspnet.md.

Existing users see no behaviour change. The analyzer walks base types up to the non-generic WebApplicationTest, so its diagnostics still apply. TUnit.PublicAPI does not cover TUnit.AspNetCore.

public class CheckoutTests : PerTestWebApplicationTest<WebApplicationFactory, Program>
{
    [Test]
    public async Task Checkout_Fails_When_Payment_Is_Declined()
    {
        var payments = new FakePaymentGateway(succeed: false);

        var factory = await CreateFactoryAsync(builder =>
            builder.ConfigureTestServices(services =>
                services.ReplaceService<IPaymentGateway>(payments)));

        using var client = factory.CreateClient();
        // ...
    }
}

Test plan

• New CreateFactoryAsyncTests.cs (8 tests): no app built before the test in on-demand mode, service and configuration layering, test context and X-TUnit-TestId wiring kept, separate apps per call, disposal of all factories, eager Factory untouched by CreateFactoryAsync. Passing on net8.0 and net10.0.
• Full TUnit.AspNetCore.Tests on net10.0: 116 passed.
• TUnit.AspNetCore.Analyzers.Tests: 90 passed.
• New docs snippet compiled locally with warnings as errors (full package-based snippet verification left to CI).

Summary by CodeRabbit

• New Features
  • Added on-demand web application setup for tests, allowing applications to be created only when needed.
  • Tests can create multiple independently configured applications, with each instance isolated and automatically disposed after the test.
  • Per-application configuration is applied after class-level configuration, while existing test setup and context wiring remain available.
  • Class-level fixtures can create additional applications without replacing their default, and cleanup continues even if one application fails to dispose.
• Documentation
  • Added guidance and examples for configuring multiple applications within a test and choosing per-test settings when they differ across tests.

[chatgpt-codex-connector]

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📝 Code Review	✅ Completed 2026-10-13T15:46:57.260568Z	fb5fa5e	New commits

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• docs/docs/examples/aspnet.md
• src/TUnit.AspNetCore.Core/WebApplicationTest.cs
• tests/TUnit.AspNetCore.Tests/CreateFactoryAsyncTests.cs

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📝 Walkthrough

Adds PerTestWebApplicationTest<TFactory, TEntryPoint> and CreateFactoryAsync for creating and tracking separately configured factories during a test. Updates WebApplicationTest<TFactory, TEntryPoint> to use the shared lifecycle while retaining its default Factory and Services properties.

Changes: ASP.NET test factory creation

Layer / File(s)	Summary
Per-test factory lifecycle src/TUnit.AspNetCore.Core/WebApplicationTest.cs, tests/TUnit.AspNetCore.Tests/CreateFactoryAsyncTests.cs, docs/docs/examples/aspnet.md	The new base runs setup before factory creation, applies class-level and optional per-call configuration, initializes services, and tracks each factory. Tests cover setup timing, configuration, test-context wiring, and separate factories. Documentation describes the API and its configuration behavior.
Tracked factory disposal src/TUnit.AspNetCore.Core/WebApplicationTest.cs, tests/TUnit.AspNetCore.Tests/CreateFactoryAsyncTests.cs	Disposal attempts every tracked factory. A single exception is rethrown with its original stack, and multiple exceptions are aggregated. Tests cover concurrent creation and continued disposal after a failure.
Existing test base integration src/TUnit.AspNetCore.Core/WebApplicationTest.cs, tests/TUnit.AspNetCore.Tests/CreateFactoryAsyncTests.cs	WebApplicationTest now derives from the per-test base and creates its default factory through the shared setup hook. Tests verify that an additional factory does not replace the default and that disposal covers both factories. HTTP capture uses ConfiguredOptions.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant Test
  participant PerTestWebApplicationTest
  participant TUnitTestContext
  participant TracedWebApplicationFactory
  Test->>PerTestWebApplicationTest: Call CreateFactoryAsync
  PerTestWebApplicationTest->>TUnitTestContext: Require running test context
  PerTestWebApplicationTest->>TracedWebApplicationFactory: Create and track configured factory
  PerTestWebApplicationTest->>TracedWebApplicationFactory: Initialize services
  TracedWebApplicationFactory-->>Test: Return factory
  PerTestWebApplicationTest->>TracedWebApplicationFactory: Dispose tracked factories after test

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Merge Risk: 🔵 Low · up to fb5fa

Concurrent factory creation is tracked correctly. A timed-out test can still leave a host running after cleanup; this is a bounded lifecycle risk to accept or address before merging.

Pre-merge checks · 4 · 1

Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 12.50% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 24 functions across 2 files. (1 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks (4 passed)

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: adding PerTestWebApplicationTest with per-test CreateFactoryAsync support.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 12.50% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 24 functions across 2 files. (1 skipped: 1 unsupported.)

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[github-actions]

Review of #7047

Overall this is a clean, well-scoped change. Extracting the shared wiring into OnDemandWebApplicationTest and layering WebApplicationTest on top avoids a throwing Factory property. It keeps existing users source-compatible, and the tests cover the main behaviours (nothing built before the test, layering order, wiring, disposal).

Two robustness points worth considering:

1. Disposal isn't failure-isolated. DisposeFactoryAsync awaits each factory in a loop. If one DisposeAsync throws, the remaining factories are never disposed, and _factories is never reset. With several factories per test, hosts (and anything like containers they hold) can leak. Wrap each disposal in try/catch, collect the exceptions, and throw an AggregateException at the end. Alternatively, null out _factories first and dispose from a local copy.

2. _factories is a plain List mutated from CreateFactoryAsync. A test that builds several apps concurrently, for example Task.WhenAll(CreateFactoryAsync(..), CreateFactoryAsync(..)), would race on Add. The init semaphore doesn't cover this, because the add happens before it. A lock around the add, or a ConcurrentBag, is cheap insurance. It would also be good to note in the docs whether concurrent calls are supported.

Minor: the CreateFactoryAsync XML docs say it throws when called outside a running test. That check uses TestContext.Current, which is fine. A test for that path is missing, but it isn't essential.

No blocking issues. Nice work.

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Reviewed commit: 6406c847c7

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Actionable comments posted: 1

---

• 🪄 Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @src/TUnit.AspNetCore.Core/WebApplicationTest.cs:
- Around line 196-201: Update the cleanup loop in WebApplicationTest to attempt
DisposeAsync on every tracked factory even when an earlier call throws. Clear
_factories before disposal so cleanup state is reset on failure, collect
disposal exceptions, and throw them together as an AggregateException after all
factories have been processed.

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[github-actions]

Review of PR 7047. I read the diff and did not build or run the tests. The skill run failed, so this was a manual review. The design is clean. Splitting the shared wiring into PerTestWebApplicationTest leaves WebApplicationTest behaving as before and avoids a Factory property that throws when it isn't set up. Failures during host build are tracked before the build, so the factory is still disposed. The tests cover layering, wiring, separate instances and disposal.

Concerns

1. _factories is not thread-safe. The code does '(_factories ??= []).Add(factory)' with no synchronisation, and DisposeFactoryAsync iterates the list. A test that builds two applications in parallel (await Task.WhenAll(CreateFactoryAsync(a), CreateFactoryAsync(b))) is a plausible use. The await on the semaphore lets continuations run on different threads. The ??= and Add calls can race, losing a factory (it is never disposed) or throwing. Guard the list with a lock, or use a ConcurrentQueue. The registration is cheap and happens once per factory, so this costs little.

2. Dispose failures can leak the remaining factories. If one factory.DisposeAsync() throws, the loop exits and the other factories are not disposed. Dispose every factory, collect the exceptions, and rethrow an AggregateException at the end. This matters more now that a test can own several factories.

3. Hook discovery in both modes. InitializeFactoryAsync now calls the private protected virtual OnSetupCompletedAsync, which keeps the same order as before: options, then SetupAsync, then the default factory. Please confirm that the Before/After hooks declared on the generic base are still discovered for PerTestWebApplicationTest in both source-generated and reflection modes. AGENTS.md requires both modes for metadata changes.

4. Smaller points.

   • CreateFactoryAsync is documented as throwing outside a running test, but there is no test for the TestContext.Current == null path.
   • The PR description says the analyzer still applies because it walks base types up to the non-generic WebApplicationTest. I did not verify that. An analyzer test with a PerTestWebApplicationTest subclass would back the claim.

Nothing blocking beyond items 1 and 2, which are both easy to fix.

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⚠️ Outside diff range comments (1)

🟡 Minor · Synchronize factory tracking for concurrent calls. · WebApplicationTest.cs:177

src/TUnit.AspNetCore.Core/WebApplicationTest.cs:177
🩺 Stability & Availability | 🟡 Minor | ⚡ Quick win

Synchronize factory tracking for concurrent calls.

If a test starts multiple CreateFactoryAsync calls concurrently, the calls can create or modify _factories at the same time. A factory can be lost from the list and remain undisposed after the test. Protect list initialization and insertion with one lock, or use a thread-safe collection.

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Review comment at @src/TUnit.AspNetCore.Core/WebApplicationTest.cs at line 177:
Synchronize `_factories` initialization and insertion in the
`CreateFactoryAsync` flow so concurrent calls cannot lose a factory; use one
lock for both operations or a thread-safe collection, while preserving the
existing factory tracking behavior.

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Outside diff comments:
Review comments at @src/TUnit.AspNetCore.Core/WebApplicationTest.cs:
- Line 177: Synchronize `_factories` initialization and insertion in the
`CreateFactoryAsync` flow so concurrent calls cannot lose a factory; use one
lock for both operations or a thread-safe collection, while preserving the
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[greptile-apps]

Confidence Score: 5/5

[Medium impact] The PR appears safe to merge; all three previous findings are addressed.

Summary

Adds PerTestWebApplicationTest for applications created inside individual tests.

• Tests can build an app with settings chosen inside the test.
• Every app created for a test is cleaned up afterward.
• The standard test base keeps its default app and can build extras.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    Setup["ConfigureTestOptions and SetupAsync"] --> Mode{"Test base"}
    Mode -->|WebApplicationTest| Eager["Build default Factory"]
    Mode -->|PerTestWebApplicationTest| Body["Run test"]
    Eager --> Body
    Body --> Create["Call CreateFactoryAsync as needed"]
    Create --> Configure["Apply class settings, then per-call settings"]
    Configure --> Track["Track factory under lock"]
    Track --> Build["Build application under shared semaphore"]
    Build --> Cleanup["Dispose every tracked factory"]
    Cleanup --> Errors["Report collected cleanup errors"]

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[github-actions]

Review

I reviewed the diff by reading it. I did not build the project or run the tests, and the code-review skill failed to start.

The design is clean. Putting the shared wiring in PerTestWebApplicationTest and keeping the eager Factory, Services and HttpCapture on WebApplicationTest means no member exists that throws when unused. The private protected virtual OnSetupCompletedAsync hook is a minimal extension point.

• Disposal: a factory is tracked before its host build, so a failed build is still disposed. Disposal continues past an earlier failure, and the exceptions are rethrown as the single exception or an AggregateException. The list is locked, which suits concurrent CreateFactoryAsync calls.
• Layering: the user delegate runs after ConfigureWebHostBuilder, as documented. The semaphore only guards the synchronous host build.
• Tests and docs: the eight new tests cover the important behaviours, and the docs section and API row match the code.

Points for you to check:

1. Binary compatibility: WebApplicationTest<,> now inherits from a new intermediate class, and GlobalFactory, the hooks and the override methods moved to it. This is source-compatible. Assemblies compiled against an older TUnit.AspNetCore would need a rebuild. That is probably fine for a test library, but the release notes could mention it.
2. EnableHttpExchangeCapture on PerTestWebApplicationTest: ConfiguredOptions is shared, but HttpCapture is only exposed on WebApplicationTest. If a user enables capture in ConfigureTestOptions on the per-test class, they have no way to read it. Either expose HttpCapture on the base or document that the option is unsupported there.
3. Disposal exceptions: ExceptionDispatchInfo.Capture(single).Throw() is correct. Plain throw would give the same result for the single-exception case if you want to simplify.

Overall, this looks good to merge once point 2 is addressed or documented.