given2

Given2

Yet another way to make the process of testing in JavaScript better.

Currently given2 supports only jasmine, mocha and jest.

Basically the given helper will register a beforeEach and a afterEach hook that will create a memoized get accessor with the given name. The value will be cached across multiple test suits in the same example but not across examples.

Note that given variables is lazy-evaluated: data in the variables are not calculated until they are accessed for the first time.

Installation

You can install given2 using npm or yarn

npm install given2
yarn add given2

Usage

To use given you just need to require or import the given2 module in your spec files

import given from 'given2'

describe('Example', () => {
  given('foo', () => 'bar');

  it('foo should be "bar"', () => {
    expect(given.foo).toBe('bar');
  })
})

More examples

The given2 variables are evaluated only once and are cached within a single test suite, and reset the cache after each suite.

let count = 0;

describe('given', () => {
  given('count', () => count += 1);

  // The values cached in same examples
  it('memoizes the value', () => {
    expect(given.count).toBe(1);
    expect(given.count).toBe(1);
  });

  // But do not cached across examples
  it('is not cached across examples', () => {
    expect(given.count).toBe(2);
  });
});

The values must be functions otherwise you will get an error.

describe('given', () => {
  it('should throw error', () => {
    // Such use will cause an error
    expect(() => given('value', 123)).toThrow();
  });
});

When you try to use the variable given, recursively given2 tells you about it.

describe('given', () => {
  // Such use will cause an error
  given('one', () => given.one);

  it('should throw error', () => {
    expect(() => given.one).toThrow();
  });
});

If you want the variable values not to be cached, use @ prefix. All variables that begin with this prefix will not be cached.

describe('given', () => {
  given('@random', () => Math.random());

  it('should not cache', () => {
    const cached = given.random;

    // values not cached
    expect(given.random).not.toBe(cached);
    expect(given.random).not.toBe(cached);
  });
});

Also you can get the values of the variables immediately, right after the declaration, with the prefix '!'

describe('given', () => {
  given('!invoice', () => {
    const invoice = Invoice.create({ price: 5 })
    invoice.paid(3)
    return invoice;
  });

  given('status', () => given.invoice);

  it('should be "paid"', () => {
    expect(given.status).toBe("paid");
  });
});