/intro-to-tdd

Primary LanguageJavaScript

TDD with Mocha & Chai

Big props to andydlindsay @ LHL Vancouver for parts of these notes/demo ✊

Agenda

  • Modules & npm, a ❤️ story
  • Practicing unit testing using a Test-Driven Development (TDD) methodology
  • Using the Mocha BDD test framework
  • Using the Chai assertion library
  • Creating and consuming modules using Node's default CommonJS sytax (module.exports and require)

TDD

  • Test Driven Development
  • Tests are written before the code is written
  • We use a process called Red-Green-Refactor
  • Red: The test is failing
  • Green: The test is passing
  • Refactor: Improve the existing code safe in the knowledge that the functionality is testable
  • BDD: Behaviour Driven Development
    • Very similar to TDD, but the focus is more on the end user rather than the quality of the code under test

Mocha

  • A testing framework
  • By default, looks in the test folder for test files to run

Chai

  • An assertion library
  • We can use assertions to describe the desired outcome of our code
  • Chai offers three different interfaces should, expect, and assert
  • For most uses, choosing which interface to use is a matter of preference
// should
myVar.should.be.a("string");
myVar.should.equal("hello world");

// expect
expect(myVar).to.be.a("string");
expect(myVar).to.equal("hello world");

// assert
assert.typeOf(myVar, "string");
assert.equal(myVar, "hello world");

module.exports and require

  • We can export functions, objects, etc from a file using the module.exports object
  • You can add new keys to the module.exports object or you can completely overwrite it with a function/object
// adding new keys to module.exports
module.exports.myFunc = myFunc;
module.exports.myOtherFunc = myOtherFunc;

// overwriting module.exports object
module.exports = myFunc;
// or
module.exports = {
  myFunc,
  myOtherFunc
};
  • As you have previously seen, we can bring functions, objects, etc into a file using require
// basic require syntax
const myFunc = require("./myFunc");

// if the file exports an object, we can use ES6 destructuring
const { myFunc } = require("./myFunc");

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