A name like this_code_sucks_and_these_tests_wre_order_dependent would be much more appropriate. It'd still be a name that would at least raise some eyebrows during code review so you'd have to write some kind of explanation why you're enabling this.
https://github.com/rails/rails/blob/6ffb29d24e05abbd9ffe3ea9...
So the "I" refers not to the general user of the function, but to the implementer of the functionality, it seems. Code philology of the day!
First, the flag is provided by minitest. That commit is an implementation of the flag in Rails.
Second, 6ffb29d moved it to prevent Rails's test framework from setting it _by default_. 281f488[1] actually added it to Rails.
minitest/minitest#a4553e2[2] appears to have added the docstring and test case to minitest.
1: https://github.com/rails/rails/commit/281f488fffc176084bf77c...
2: https://github.com/minitest/minitest/commit/a4553e2e127072c9...
1. From https://github.com/rails/rails/blob/6ffb29d24e05abbd9ffe3ea9..., click "Blame" on the header bar over the file contents.
2. Scroll down to the line and click on the commit in the left column.
3. Scroll down to the part of the commit that removed the line from its previous location, in activesupport/lib/active_support/test_case.rb.
4. Click the three-dots menu in that file's header bar and select "View file".
5. Click "History" in the header bar of the contributors, above the file contents.
6. I guessed here that it was introduced in commit 281f488 based on its message: "Use the method provided by minitest to make tests order dependent". Clicking through to it confirms that. There's also a comment here that identified the problem which led to, and provided context for, the change in 6ffb29d.
The OP is from minitest's documentation, so to find the introduction in minitest, it's basically the same process.
1. Go to https://github.com/minitest/minitest.
2. Search the repo for the method name. Even just "i_suck" will match the commit.
3. Select the oldest commit in the results. That's a4553e2.