ci: Pass tests under macOS

[hyperupcall]

Related: Fixes #294

Description

This fixes the tests so macOS CI passes. There were two main issues:

• osx wc printing unexpected spaces
  • trimmed the spaces with tr
• set -U not working on macOS (currently fish version 3.7)
  • to fix this, erasing the variable before setting it somehow made it work

First contribution?

Check the 👍 Contribute section and the contributing guide.

Acceptance Checks

• documentation is up-to-date:
  • features list ;
  • Prompt Symbol ;
  • 🔌 Features' Flags ;
• feature flag is present in conf.d/pure.fish ;
• symbol is present in conf.d/pure.fish ;
• tests are passing (I can help you 🤗 ):
  • config are tested (cf. tests/_pure.test.fish) ;
  • feature is covered ;
• customization is available ;
• feature is implemented.

[edouard-lopez]

Thanks for the contribution!
Some changes to do and we should be good

[hyperupcall]

@edouard-lopez I've updated the tests to use a dedicated container test for macOS and Linux, but I don't think it's possible to specify a particular version of Fish to install with Homebrew. Usually, only the latest versions are supported. Some applications like postgres do have multiple versions and some applications do have custom taps with multiple versions, but that does not seem to be the case for Fish. Maybe that could be fixed by someone a follow-up PR?

[edouard-lopez]

I introduced a regression with the code I suggested that added an extra end on each block. Could you update and then rebase on master ?

[edouard-lopez]

There is an issue with not ok 97 _pure_is_inside_container: true for Github Action on Ubuntu. I will have a look

[edouard-lopez]

The failure was due to error in the test file (not cleaning a mocked method), I will fix in #347