Write BDD-style tests with eloquence.

“What's this?”

This is a drop-in enhancement for Mocha's BDD interface, which adds two small but tangible improvements:

A when() global

This is the same calling describe(), but the description you give is automatically prefixed by "When ":

when("this test is run", () => {
    it('gets prepended with the word "When"', …);

Which is a shorter, clearer way of writing:

describe("when this test is run", () => …);

Tests specified by it() actually start with "It "

Mocha makes idiomatic tests fun to write ...

describe("when the app starts", () => {
    it("activates successfully", () => …);
    it("connects to the server", () => …);
    it("receives a valid payload", () => …);

... but not as fun to read:

when the app starts
  ✓ activates successfully
  ✓ connects to the server
  ✓ receives a valid payload
  ✓ displays the result

This module fixes such broken language by automatically prefixing each test:

when the app starts
  ✓ it activates successfully
  ✓ it connects to the server
  ✓ it receives a valid payload
  ✓ it displays the result

If a test (or suite) description already includes the expected prefix, it won't be modified. So you needn't worry about stuff like this:

when When the prefix is included
  ✓ it it won't repeat the word "it"
  ✓ it it'll check for contractions too


  1. Add mocha-when to your project's dependencies: ~~~sh # Using NPM: npm install --save-dev mocha-when
# Or with Yarn:
yarn add mocha-when
  1. Activate it by calling the function it exports: ~~~js require("mocha-when")(); ~~~ Or simply pass mocha-when/register to Mocha's require option: ~~~js // In your .mocharc.js file: module.exports = { require: [ "mocha-when/register", ] }; ~~~


  • ESLint won't recognise the when() global, so add it to your globals list.
  • Mocha's ui option is assumed to be bdd (the default).
  • Tests can be declared without an it prefix using specify().
  • The enhancements applied by this module are persistent and irrevocable.