The module template uses Jest as a standard test library. We should migrate from Mocha/Chai to it.

• Remove mocha, chai, and chai-spies as dependencies and replace it with jest
• Copy jest.config.js from the module template
• Convert existing tests from Mocha/Chai syntax to Jest
• Replace the test script in package.json with the equivalent jest line (see the module template), and add a test:watch script
• Run yarn test. If Jest does not report that 100% test coverage has not been achieved, then add jest-it-up as a development dependency; otherwise, adjust the coverage thresholds in jest.config.js to match the numbers reported.