[RF-DOCS] Update Rails Testing Guide [ci skip]

[OughtPuts]

Motivation / Background

This Pull Request has been created to update the testing guide.

Detail

• Section order has been changed to improve the flow of the guide.
• Mostly, the wording has been changed for ease of understanding, brevity and readability.
• assert_routing was added to the rails assertions.
• Quite a few updates were made to the 'Functional Testing for Controllers' section, particularly around generating test scaffold code.

Additional information

For discussion:

• I've seen in my original notes that I thought about splitting this guide into two - almost a 'beginners testing' and 'advanced testing' - any opinions on this would be welcome, as the changes made to this guide would stay relevant in two halves.

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Unrelated changes should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.

[bhumi1102]

Reviewed up to line 500

[bhumi1102]

Reviewed up to line 1000 😊

[bhumi1102]

Finished my review. This was a long one, thanks @OughtPuts for working through it!

[Ridhwana]

This was a really long guide, and you've made some excellent updates, @OughtPuts! 💛 Thank you! ✨

I left some feedback—feel free to incorporate what you find valuable. One thing I did notice is the shift between using "we/our" and "you" throughout the guide, which felt a bit inconsistent. It seems to have carried over from the initial version.

While it's perfectly fine to use those pronouns when necessary, I find that the tone of the most of the guides (at least the newer ones) tends to lean more toward neutral language or the use of "you." I believe @bhumi1102 follows a similar approach (based on reviewing her work), but I stand to be corrected. Either way, it's a discussion worth having if we need to 😊 .