TST: new set of tests to the Flight class

[Gui-FernandesBR]

Pull request type

Please check the type of change your PR introduces:

• Other (please describe): Unit tests

Pull request checklist

Please check if your PR fulfills the following requirements, depending on the type of PR:

• Code base additions (for bug fixes / features):

  • Tests for the changes have been added
  • Docs have been reviewed and added / updated if needed
  • Lint (black rocketpy) has passed locally and any fixes were made
  • All tests (pytest --runslow) have passed locally

What is the current behavior?

• The current tests covering the Flight class barely tests the results of the class. Instead, it only check if the class is running without errors. This is a kind of poor testing as it does not give us enough faith on the results if we modify the Flight Class.
• What I propose is for us to set tests checking numeric outputs from the class, thus ensuring that we will always have a way to copare the new flight simulations against the ones

What is the new behavior?

• (1) For some specific methods, now we have tests checking if the class is returning the expected values, with those being the results extracted from the simulation as it is today.
• (2) On other hand, some tests are checking if the class is returning the correct value compared against the exact expected value (calculated by hand).
• I documented every test so we can easily differentiate (1) and (2)
• I separated the tests by logic, this way I believe is easier for us to debug the code in the future. Specifically, you're gonna see some very similar methods at the bottom of the test_flight.py file. ButI throught it would be worse to have everything being test under the same function.
• As a painpoint of making more narrow tests like this, we probably will need to change te expected values of several method if we find a serious bug in the code. (but we don't think there's space for such error in the current state of the code, right?)

Does this introduce a breaking change?

• No

Other information

• Please review the BUG: absolute value of the rail button forces #407 first, and then we can change the head branch to beta/v1.0.0
• Being 100% transparent here: I created all these tests because I want to change the way we calculate R1, R2, R3, M1, M2 and M3 arguments, and therefore I'd love to have better tests to support my changes in a future PR. The Flight class needs an overhaul, so I think more robust tests are coming one way or another

[Gui-FernandesBR]

And of course it didn't work out of windows system (great!!)

I'm converting this to draft, temporarily

[Gui-FernandesBR]

Merging the develop branch into this one actually solved the problem that was blocking this PR.
So I believe we are good to go!

I can't merge it bc we need an approval first. Asking for help here.

[phmbressan]

Good. I have updated some old docstrings in my latest commits.

Before merging, I would only double check if the numbers of the new tests are still valid (the ones that come from sim results) since there was a gap of time between this PR being implmented and now.