All assertions should be made using unexpected, unless there's a good reason not to. Exceptions include:
Testing diff output. Mocha generates diff output unless the assertion library decides to do this itself. Since unexpected generates its own diff output, we need to use an assertion library that does not; we use the built-in assert module.
test/unit/runnable.spec.js must avoid 3rd-party code; read source for more info
Tests asserting interop with other specific assertion libraries.
All tests have extension .spec.js.
All test fixtures have extension .fixture.js.
All test fixtures are ignored by ESLint.
mocha.opts will require test/setup.js, which is the main harness.
test/assertions.js contains Mocha-specific types and assertions for unexpected
test/node-unit/ only runs in Node.js; test/browser-specific/ only runs in the browser.
See ../karma.conf.js for more information on which tests run in the browser.
We can't run all of the Node.js tests in one mocha command, because we need to use different command-line options to test the various reporters and interfaces.
See ../package-scripts.js for more info about how things are split up.