Refactor Tests

[takameyer]

What, How & Why?

This is the feature branch for refactoring the legacy tests, located at tests, into TypeScript/mocha based tests, located in integration-tests.

This closes # ???

☑️ ToDos

• [ ] 📝 Changelog entry
• [ ] 📝 Compatibility label is updated or copied from previous entry
• [ ] 🚦 Tests
• [ ] 🔀 Executed flexible sync tests locally if modifying flexible sync
• [ ] 📱 Check the React Native/other sample apps work if necessary
• [ ] 📝 Public documentation PR created or is not necessary
• [ ] 💥 Breaking label has been applied or is not necessary

If this PR adds or changes public API's:

• [ ] typescript definitions file is updated
• [ ] jsdoc files updated
• [ ] Chrome debug API is updated if API is available on React Native