Integration tests documentation add nunit mstest

[jonorogers]

This PR adds support for xUnit & NUnit into the integration tests documentation; including snippets for all three popular testing libraries (xUnit, MSTest, NUnit). This PR follows the examples of already exisiting MS documentation i.e. https://learn.microsoft.com/en-us/dotnet/aspire/testing/write-your-first-test?pivots=mstest

I'm submitting a PR as suggested by @tdykstra here: #35290 (comment)

Notes:

• I haven't updated the sample project in AspNetCore.Docs.Samples - this could be useful to add another two testing projects, but I wasn't sure what the scope of this PR should be.
• Some of the article text still references xUnit; as it's describing the samples project. I'm not sure if this is now confusing, as the pivot groups aren't referencing xUnit if it's not selected.
• In MSTest I personally favour using [AssemblyInitialize] rather than [ClassInitialize] when instantiating a WebApplicationFactory in integration tests, but I opted for equivalence between the three examples.
• I noticed that the samples are split up by .NET versions, but I have opted instead to follow the example of the Aspire docs linked above and just provide snippets in C# for the three unit testing frameworks.
• I have no idea if there is any other code which needs to be modified to support the additional pivot group declaration.

Fixes #35290

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Internal previews

📄 File	🔗 Preview link
aspnetcore/test/integration-tests.md	Integration tests in ASP.NET Core
aspnetcore/zone-pivot-groups.yml	aspnetcore/zone-pivot-groups

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[Copilot]

Pull Request Overview

This PR expands the integration tests documentation to include MSTest and NUnit examples alongside the existing xUnit snippets by updating pivot groups and adding corresponding code samples.

• Added a new pivot group ("Unit testing framework") in the zone-pivot-groups.yml file.
• Introduced multi-framework integration test snippets for xUnit, MSTest, and NUnit across various test files (IndexPageTests, BasicTests, AuthTests, CustomWebApplicationFactory).
• Updated integration tests markdown to reference the new unit-testing-framework pivot group.

Reviewed Changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
aspnetcore/zone-pivot-groups.yml	Added a new pivot group for unit testing frameworks with xUnit, MSTest, and NUnit.
aspnetcore/test/integration-tests/snippets/xunit/*	Added xUnit integration test snippets with multiple test methods.
aspnetcore/test/integration-tests/snippets/mstest/*	Added MSTest integration test snippets mirroring the xUnit examples.
aspnetcore/test/integration-tests/snippets/nunit/*	Added NUnit integration test snippets mirroring the xUnit examples.
aspnetcore/test/integration-tests/includes/integration-tests9.md	Updated documentation to include new pivot zones for unit-testing-framework.
aspnetcore/test/integration-tests.md	Added zone_pivot_groups configuration and updated code snippet inclusions for multiple frameworks.

[Rick-Anderson]

@benhopkinstech @timdeschryver @profet23 please review

[timdeschryver]

The examples are looking good to me to me.
For some reason the snipping are not showing up for me while running docfx serve.

But I do have a couple of remarks (which can be handled in separate PRs I suppose):

• Throughout the article there are still some references to xUnit specifics, e.g. in https://learn.microsoft.com/en-us/aspnet/core/test/integration-tests?view=aspnetcore-9.0#test-app-prerequisites and https://learn.microsoft.com/en-us/aspnet/core/test/integration-tests?view=aspnetcore-9.0#disable-shadow-copying. What do we want to do with this?
• Should the sample be updated in the Samples repo? This means the class HttpClientExtensions (which is also referenced in this article) needs to be updated.

[timdeschryver]

For highlights you can do the following:

Suggested change

	:::code language="csharp" source="../snippets/xunit/IntegrationTests/IndexPageTests.cs?name=snippet5&highlight=7-10,17,20-21":::
	:::code language="csharp" source="../snippets/xunit/IntegrationTests/IndexPageTests.cs" id="snippet5" highlight="7-10,17,20-21":::

[timdeschryver]

I think this is easier to read and recommended, I could be wrong though.

Suggested change

	:::code language="csharp" source="../snippets/xunit/IntegrationTests/BasicTests.cs?name=snippet1":::
	:::code language="csharp" source="../snippets/xunit/IntegrationTests/BasicTests.cs" id="snippet1":::

[profet23]

Maybe tagging wrong person? Happy to take a look.

[jonorogers]

Thanks @timdeschryver , I've updated all the snippets to your provided syntax; I can see them properly loading in docfx now..

I also re-formatted the new snippets as they didn't follow the .net coding conventions (love me some K&R braces); so the highlight lines were off.

I'd be happy to update the sample instead of adding snippets if you think that would bring more value/be easier to maintain in the future.

[timdeschryver]

This is looking better, thanks for the updates @jonorogers !
Do you also want to update the code snippets in integration-tests9.md please.

I verified the code snippets are:

• are correct from a technical side
• are displayed (and highlighted) correctly in the docs

@Rick-Anderson when you have the time can you take a look at my previous comment and determine how you want to proceed with this please?
In summary:

• Do we want to have the samples in the Samples repository?
• Do we want to update the other references to xUnit as well in this article?

[timdeschryver]

This needs an extra highlighted line

Suggested change

	:::code language="csharp" source="integration-tests/snippets/nunit/IntegrationTests/IndexPageTests.cs" id="snippet5" highlight="7-10,17,20-21":::
	:::code language="csharp" source="integration-tests/snippets/nunit/IntegrationTests/IndexPageTests.cs" id="snippet5" highlight="7-10,17,20-22":::

[jonorogers]

Thanks, have updated the PR with the updated integration-tests9.md and both files have the highlighted line added