jest-matcher-structure

jest-matcher-structure

A custom jest matcher for validating object structures

Install • Usage • List of Comparisons • TODO • Created By • License

Install

$ npm install --save-dev jest-matcher-structure

Usage

jest-matcher-structure walks key-by-key through a structure object and a comparison object and verifies that the value in the structure object accurately describes the value in the comparison object.

It's easy to get started! Here's a quick and simple example:

import { toMatchStructure } from 'jest-matcher-structure'

expect.extend({ toMatchStructure })

test("structure matches object's structure", () => {
  const structure = {
    string: 'string',
    number: 'number',
    boolean: 'boolean',
    function: n => n > 5,
    literal: 'literal value',
    nested: {
      string: 'string',
      number: 'number',
      function: n => x < 5,
    },
    arrayLiteral: ['hello', 'hi', 1, 2, 3, true, false],
    regex: /\d+/,
    null: null,
  }

  const object = {
    string: 'hello world',
    number: 123,
    boolean: true,
    function: 10,
    literal: 'literal value',
    nested: {
      string: 'string',
      number: 1,
      function: 3,
    },
    arrayLiteral: [false, true, 3, 2, 1, 'hi', 'hello'],
    regex: '1234',
    null: null,
  }

  expect(structure).toMatchStructure(object)
})

Helper Functions

jest-matcher-structure comes with the helper functions some, every, and repeat.

some and every are for fields where you need to test the comparison value against multiple truths. You pass them an array and jest-matcher-structure works its magic! Here's an example:

import { some, every, toMatchStructure } from 'jest-matcher-structure'

test('some and every', () => {
  const structure = {
    field1: some(['A', 'B']),
    field2: every(['string', x => x >= 1200 && x <= 1500]),
  }

  const object = {
    field1: 'A',
    field2: '1300',
  }

  expect(structure).toMatchStructure(object)
})

repeat is for consuming repeating comparisons in an array. For example, if you need to make sure an array is filled with strings, you can do the following:

import { repeat, toMatchStructure } from 'jest-matcher-structure'

test('repeat', () => {
  const structure = {
    field1: [repeat('string')],
  }

  const object = {
    field1: ['hello', 'world', 'fubar'],
  }

  expect(structure).toMatchStructure(object)
})

List of Comparisons

• literal value
• string type
• number type
• boolean type
• function
• regex
• some
• every
• objects
• arrays
  • exact comparison match
  • repeating values in an array using repeat

Upcoming Changes

• Code refactor
• Flesh out test cases to make sure edge cases are covered
• Rethink some, every, repeat

Created By

• Mark Chandler

License

MIT