Add testing platform architecture

[Evangelink]

Summary

Move and reorganize the architecture/extensibility documentation for the new testing platform.

cc @MarcoRossignoli

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Internal previews

📄 File	🔗 Preview link
docs/core/testing/unit-testing-platform-architecture-capabilities.md	docs/core/testing/unit-testing-platform-architecture-capabilities
docs/core/testing/unit-testing-platform-architecture-extensions.md	docs/core/testing/unit-testing-platform-architecture-extensions
docs/core/testing/unit-testing-platform-architecture-services.md	docs/core/testing/unit-testing-platform-architecture-services
docs/core/testing/unit-testing-platform-architecture.md	docs/core/testing/unit-testing-platform-architecture
docs/core/testing/unit-testing-platform-exit-codes.md	docs/core/testing/unit-testing-platform-exit-codes
docs/core/testing/unit-testing-platform-intro.md	docs/core/testing/unit-testing-platform-intro

[MarcoRossignoli]

I don't see the image and the mermaid rendering correctly is it related only to the "preview"?

[Evangelink]

@IEvangelist Are our docs supporting mermaid?

[IEvangelist]

I'm still not done with this review, it's taking a really long time - been working on it for a while now. I'm going to comment on it, and return when I can focus a bit more. But for now, here's what I have.

[IEvangelist]

I don't like this diagram. What's it trying to convey exactly? We need all the text in the image to be the same size, and the colors (typically pastel colors are better) aren't very appealing. While some of this is opinion, let's see if we can't do a bit better. I strive to use Excalidraw for consistency. You can then export the file for others to collaborate on, and add that to source control too. The legend should be on the bottom left, and instead of the shape + color, just used a square with the color. Does the shared bus also ever report back to the test framework?

[Evangelink]

Any extension to the new platform (including Test Framework) can publish or subscribe to data from the message bus.

[Evangelink]

I'll suggest a different design based on the tool you suggested, thanks!

[Evangelink]

cc @MarcoRossignoli

[Evangelink]

I'm still not done with this review, it's taking a really long time - been working on it for a while now.

Thank you so much for everything you have reviewed already! We know this is a super big change, I have read it a few times and I am still not 100% happy with the results of what we wrote nor the structure but it's not always easy to get the abstraction of knowing all the implementation details.

[IEvangelist]

There are still a few things that we'll need to update, this is starting to shape up though. Let's consider this 2/3 in terms of reviews. 🤓

[IEvangelist]

I've checked back on this one a few times, there's still a lot of suggestions that haven't been resolved. I'll come back once those are addressed. /cc @Evangelink

[Evangelink]

@IEvangelist Yes sorry! I have been pretty busy with other priorities, I'll get back here early next week!

[IEvangelist]

@IEvangelist Yes sorry! I have been pretty busy with other priorities, I'll get back here early next week!

No worries, I completely understand. I just wanted to make sure I wasn't missing anything. I'm off all next week, so I'll check back the week of 8/12. Thank you, my friend! @Evangelink

[Evangelink]

Hey @IEvangelist, could we resume work on this PR? We have finished integration with xUnit v3, NUnit, and we are getting close to finishing with F# Expecto.