Epic: Refactor Test Suite

[drewbo]

As part of a broader React and related dependency upgrade, we likely need to significantly change our current test suite:

• the primary test renderer enzyme does not have a supported adapter for React 18
• the current React recommendation for test frameworks is to use jest and react-testing-library; these seemingly have better integration with newer React features than enzyme or mocha

Notes

• React Testing Overview
• React Testing Environments
• Jest
• React Testing Library
• RTL: migrate from enzyme

Tasks

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1. Organize components #4613
   +0
2. Investigate new build process with more modern tooling. #4616
   squad-pages +1
   
3. Look at improved linting and code formatting. #4617
   squad-pages +1
   
4. refactor page/component/container relationship to make components more testable #4631
   2 of 2
   squad-pages +1
   
5. Create a partial RTL-based testing suite to be run in conjunction with existing test suite #4635
   squad-pages +1
   
6. Add code coverage reporting and delta on PR #4643
   squad-pages +1
   
7. Decide on a test coverage threshold or other metric for deciding when to switch over #4642
   squad-pages +1
   
8. Add RTL test to @shared/GithubBuildBranchLink.jsx #4670
   squad-pages +1
   
9. Add RTL test to @shared/GithubBuildShaLink.jsx #4669
   squad-pages +1
   
10. Add RTL test to @shared/ButtonLink.jsx #4672
    squad-pages +1
    
11. Add RTL tests to @shared/UsaIcon.jsx #4668
    squad-pages +1
    
12. Add RTL tests to @shared/GithubAuthButton.jsx #4671
    squad-pages +1
    
13. Write up test best practices #4665
    squad-pages +1
    
14. Decide how to generate and store fixtures
15. Retire old tests
16. Outline tests to be added

[drewbo]

Started initial work on this in https://github.com/cloud-gov/pages-core/tree/refactor-test-suite and updated the acceptance criteria

[drewbo]

Update: I rebased the aforementioned branch and made a few updates to get linting + coverage working with latest main. The coverage stats show that this covers roughly 6% of the components and 4% of the whole frontend folder. An assortment of thoughts with no particular end goal:

• Switching from enzyme to RTL (without making changes to the underlying test intent) is a bit of a chore but also maybe could be partially automated with some regex?
• The non-component tests only need to be switched from chai to jest, which is mostly a matter of different assertion names. This is also a bit of a chore and maybe could be partially automated.
• The test logic itself probably needs a once over. That seems like a big undertaking to do all at once, maybe it could happen in conjunction with component updates on some sort of ongoing basis