Start migration of tests to electron-mocha

[araujoarthur0]

Related issue

Helps #1037

Context / Background

Refer to #1054.
Here I'm starting to migrate our tests to the electron-mocha infrastructure, which works well with ES6 modules.
I think I'll only be able to pre-migrate the ones that don't depend on jest-specific things, before switching fully to ES6.
Starting with the simple test tests/main/time-math.js as an example here.

What change is being introduced by this PR?

• Dependency changes
  • @babel/plugin-transform-modules-commonjs is used to convert ES6 into common js while we don't move fully to ES6.
  • electron-mocha and mocha will be the test runners we use
  • Added c8 dependency, which has the same purpose as nyc, that of a code coverage runner around mocha. Had to use this one because nyc doesn't work with electron-mocha. Anyway, c8 is considered the native replacement to nyc, and the output is exactly the same.
• Added config files for electron-mocha. Some configs like color and parallel are to make the test runs better.
• Added new npm target "test:electron-mocha-main", which is used in the test pipeline.
• Migrated time-math.js test to use mocha.
  • Removed time-math.js from the jest matching tests, now that it's migrated.
  • Added it to electron-mocha-main.config.js

How will this be tested?

Pipeline passes in the same way, coverage will be coming from two reports and is currently being merged into a single report. CodeCov is properly parsing the combination.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (8f2ae80) 80.00% compared to head (9b9c47b) 81.37%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1061      +/-   ##
==========================================
+ Coverage   80.00%   81.37%   +1.37%     
==========================================
  Files          20       22       +2     
  Lines        1270     1401     +131     
  Branches      191      214      +23     
==========================================
+ Hits         1016     1140     +124     
- Misses        254      261       +7     

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[tupaschoal]

Seems fine, actually easier than I thought, dependency changes aside, but I think that's because time-math has no stubs/mocks, right?

My comments are mostly just questions, so I'm hitting approve.

[araujoarthur0]

Seems fine, actually easier than I thought, dependency changes aside, but I think that's because time-math has no stubs/mocks, right?

Yes, I chose the simplest one to get it along with the infrastructure changes 🤣