LIttle helpers methods to help you write unit test with jest in a more "behavior oriented" way

jestTdd.js

const given = (name, cb = () => {}) => [cb, describe.bind(describe, `given ${name}`)];
const and = (name, cb = () => {}) => [cb, describe.bind(describe, `and ${name}`)];
const when = (name, cb = () => {}) => [cb, describe.bind(describe, `when ${name}`)];
const then = (name, cb = () => {}) => [cb, test.bind(test, `then ${name}`)];

const feature = (name, getSteps) => {
  const steps = [[() => {}, describe.bind(describe, 'Feature: basic synchronous command')], ...getSteps()];
  const lastStep = steps.pop();
  const [cb, step] = steps.reduceRight(([combinedCb, combinedStep], currentFn) => {
    const [cb, step] = currentFn;
    return [
      (...args) => {
        cb(...args);
        combinedStep(combinedCb);
      },
      step,
    ];
  }, lastStep);
  step(cb);
};

feature('some feature to test', () => {
  /* some state for this feature */
  return [
    given('some precondition'),
    and('another precondition'),
    when('something happens', () => {
      /* let's something to happen */
    }),
    and('other thing happens', () => {
      /* let's make another thing to happen */
    }),
    then('the invariants should not be violated', () => {
      /* test the invariants */;
    }),
  ];
});