feat(optimizer): Add optimizer unit tests and refactor (#4094)

* refactor: extract optimiser lesson option management and add unit tests

* refactor: extract unassigned lesson option filtering and add unit tests

* refactor: move optimiser test defaults into test-utils

* feat: add optimiser button unit tests

* feat: add optimiser results unit tests

* refactor: WIP refactor optimiser form

* refactor: update optimiser form styles

* feat: add format unit tests

* feat: add optimiser form unit tests

* fix: revert api path

* fix: set difference compatibility

* fix: optimiser free day toggle

* lint: remove unused import

* fix: update style issues

* fix: optimiser tooltip icon wrap

* fix: update styles

* refactor: replace enzyme with testing library

* fix: set difference compatibility

# Conflicts:
#	website/src/views/optimiser/OptimiserForm/OptimiserFreeDaySelect.tsx

* lint: remove unused import

* fix: remove hard coded value

* fix: adjust styles

* fix: update dropdown style

---------

Co-authored-by: Ravern Koh <ravernkoh@gmail.com>
Co-authored-by: Jonathan Loh <36648707+jloh02@users.noreply.github.com>

Author: 3 people

website/README.md

@@ -267,7 +267,9 @@ If a community libdef is not available, you can try writing your own and placing
 
 ### Testing and Linting
 
-We use [Jest][jest] with [Enzyme][enzyme] to test our code and React components, [TypeScript][ts] for typechecking, [Stylelint][stylelint] and [ESLint][eslint] using [Airbnb config][eslint-airbnb] and [Prettier][prettier] for linting and formatting.
+We use [Jest][jest] with [Enzyme][enzyme] and [Testing Library][testing-library] to test our code and React components, [TypeScript][ts] for typechecking, [Stylelint][stylelint] and [ESLint][eslint] using [Airbnb config][eslint-airbnb] and [Prettier][prettier] for linting and formatting.
+
+**Note: The majority of React tests are written with Enzyme. For new unit tests, please try to use [Testing Library][testing-library] instead!**
 
 ```sh
 # Run all tests once with code coverage
@@ -404,6 +406,7 @@ Components should keep their styles and tests in the same directory with the sam
 [bootstrap]: https://getbootstrap.com/
 [jest]: https://facebook.github.io/jest/
 [enzyme]: http://airbnb.io/enzyme/
+[testing-library]: https://testing-library.com/docs/react-testing-library/intro/
 [ts]: https://www.typescriptlang.org/
 [eslint]: https://eslint.org/
 [svgr]: https://github.com/smooth-code/svgr

website/package.json

@@ -42,8 +42,8 @@
     "@pmmmwh/react-refresh-webpack-plugin": "0.5.15",
     "@svgr/webpack": "8.1.0",
     "@testing-library/dom": "10.4.0",
-    "@testing-library/jest-dom": "6.6.3",
-    "@testing-library/react": "16.1.0",
+    "@testing-library/jest-dom": "^6.6.3",
+    "@testing-library/react": "^16.3.0",
     "@testing-library/user-event": "14.5.2",
     "@types/body-scroll-lock": "2.6.2",
     "@types/enzyme": "3.10.18",