Let's look at examples of the two most common interfaces for Mocha and Chai—BDD and TDD.
The Mocha BDD interface provides four main functional units:
before(): This is a setup that occurs once before all the tests within a suite are run. Mocha also provides abeforeEach()function that runs before each test in a suite.after(): This is a setup that occurs once after all tests in a suite are run, with theafterEach()alternative that runs before each test.describe(): This specifies a test suite and can be nested within otherdescribe()functions.it(): This defines a single test function containing one or more assertions.
Chai's BDD style uses expect or should to make dot-notation assertion chains.
We can create a basic test file chapters/03/test/js/spec/bdd.spec.js, which uses all of these components. We name the suite with describe(), add/remove a function with before()/after(), and test it with an it() specification declaration...