jest-extended

What is jest-extended?

jest-extended is a set of additional matchers for Jest, a popular JavaScript testing framework. It extends Jest's built-in matchers with a variety of new ones, making it easier to write more expressive and comprehensive tests.

What are jest-extended's main functionalities?

Array Matchers

Checks if the value is an array.

expect([1, 2, 3]).toBeArray();

Object Matchers

Checks if the object contains the specified key.

expect({ a: 1 }).toContainKey('a');

String Matchers

Checks if the string starts with the given substring.

expect('hello world').toStartWith('hello');

Number Matchers

Checks if the number is within the specified range.

expect(10).toBeWithin(5, 15);

Date Matchers

Checks if the date is after the specified date.

expect(new Date('2023-01-01')).toBeAfter(new Date('2022-12-31'));

Other packages similar to jest-extended

chai

Chai is an assertion library for Node.js and the browser that can be delightfully paired with any JavaScript testing framework. It provides a variety of assertion styles (should, expect, assert) and is highly extensible.

should

Should.js is an expressive, readable, and powerful assertion library for Node.js and the browser. It extends Object.prototype to provide a more natural way to write assertions.

expect

Expect is a minimalistic assertion library for JavaScript. It is often used with Jest but can be used standalone. It provides a set of simple and intuitive matchers.

README

jest-extended

🃏💪

Additional Jest matchers

---

Problem

Jest is an amazing test runner and has some awesome assertion APIs built in by default. However there are times when having more specific matchers (assertions) would be far more convenient.

Solution

jest-extended aims to add additional matchers to Jest's default ones making it easy to test everything 🙌

Contributing

If you've come here to help contribute - Thanks! Take a look at the contributing docs as a way of getting started.

---

• Problem
• Solution
• Contributing
• Installation
• Setup
• Asymmetric matchers
• API
  • .pass(message)
  • .fail(message)
  • .toBeEmpty()
  • .toBeOneOf([members])
  • .toBeNil()
  • .toSatisfy(predicate)
  • Array
    • .toBeArray()
    • .toBeArrayOfSize()
    • .toIncludeAllMembers([members])
    • .toIncludeAnyMembers([members])
    • .toIncludeSameMembers([members])
    • .toSatisfyAll(predicate)
  • Boolean
    • .toBeBoolean()
    • .toBeTrue()
    • .toBeFalse()
  • Date
    • .toBeDate()
    • .toBeValidDate()
    • .toBeAfter(date)
    • .toBeBefore(date)
    • Further proposals in #117 PRs welcome
  • Function
    • .toBeFunction()
    • .toThrowWithMessage()
  • Mock
    • .toHaveBeenCalledBefore()
    • .toHaveBeenCalledAfter()
  • Number
    • .toBeNumber()
    • .toBeNaN()
    • .toBeFinite()
    • .toBePositive()
    • .toBeNegative()
    • .toBeEven()
    • .toBeOdd()
    • .toBeWithin(start, end)
  • Object
    • .toBeObject()
    • .toContainKey(key)
    • .toContainKeys([keys])
    • .toContainAllKeys([keys])
    • .toContainAnyKeys([keys])
    • .toContainValue(value)
    • .toContainValues([values])
    • .toContainAllValues([values])
    • .toContainAnyValues([values])
    • .toContainEntry([key, value])
    • .toContainEntries([[key, value]])
    • .toContainAllEntries([[key, value]])
    • .toContainAnyEntries([[key, value]])
    • .toBeExtensible()
    • .toBeFrozen()
    • .toBeSealed()
  • Promise
    • .toResolve()
    • .toReject()
  • String
    • .toBeString()
    • .toBeHexadecimal(string)
    • .toEqualCaseInsensitive(string)
    • .toStartWith(prefix)
    • .toEndWith(suffix)
    • .toInclude(substring)
    • .toIncludeRepeated(substring, times)
    • .toIncludeMultiple([substring])
• LICENSE

Installation

With npm:

npm install --save-dev jest-extended

With yarn:

yarn add -D jest-extended

Setup

Jest >v24

Add jest-extended to your Jest setupFilesAfterEnv configuration. See for help

"jest": {
  "setupFilesAfterEnv": ["jest-extended"]
}

Jest <v23

"jest": {
  "setupTestFrameworkScriptFile": "jest-extended"
}

If you are already using another test framework, like jest-chain, then you should create a test setup file and require each of the frameworks you are using.

For example:

// ./testSetup.js
require('jest-extended');
require('jest-chain');
require('any other test framework libraries you are using');

Then in your Jest config:

"jest": {
  "setupTestFrameworkScriptFile": "./testSetup.js"
}

Typescript

If your editor does not recognise the custom jest-extended matchers, add a global.d.ts file to your project with:

import 'jest-extended';

Asymmetric matchers

All matchers described in the API are also asymmetrical since jest version 23:

test('passes when using an asymmetrical matcher', () => {
  expect([]).toEqual(expect.toBeArray());
});

API

.pass(message)

Note: Currently unimplemented

Passing assertion.

expect().pass('should pass');

.fail(message)

Note: Currently unimplemented

Failing assertion.

expect().fail('test should fail');

.toBeEmpty()

Use .toBeEmpty when checking if a String '', Array [], Object {}, or [Iterable](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#Built-in_iterables) is empty. Because toBeEmpty supports checking for emptiness of Iterables, you can use it to check whether a Map, or Set is empty, as well as checking that a generator yields no values.

test('passes when given an empty string', () => {
  expect('').toBeEmpty();
  expect('hello').not.toBeEmpty();
});

test('passes when given an empty array', () => {
  expect([]).toBeEmpty();
  expect(['hello']).not.toBeEmpty();
});

test('passes when given an empty object', () => {
  expect({}).toBeEmpty();
  expect({ hello: 'world' }).not.toBeEmpty();
});

.toBeOneOf([members])

Use .toBeOneOf when checking if a value is a member of a given Array.

test('passes when value is in given array', () => {
  expect(1).toBeOneOf([1, 2, 3]);
  expect(4).not.toBeOneOf([1, 2, 3]);
});

.toBeNil()

Use .toBeNil when checking a value is null or undefined.

test('passes when value is null or undefined', () => {
  expect(null).toBeNil();
  expect(undefined).toBeNil();
  expect(true).not.toBeNil();
});

.toSatisfy(predicate)

Use .toSatisfy when you want to use a custom matcher by supplying a predicate function that returns a Boolean.

test('passes when value passes given predicate', () => {
  const greaterThanOneButNotThree = n => n > 1 && n !== 3;
  expect(100).toSatisfy(greaterThanOneButNotThree);
  expect(0).not.toSatisfy(greaterThanOneButNotThree);
  expect(3).not.toSatisfy(greaterThanOneButNotThree);
});

Array

.toBeArray()

Use .toBeArray when checking if a value is an Array.

test('passes when value is an array', () => {
  expect([]).toBeArray();
  expect([1]).toBeArray();
  expect(true).not.toBeArray();
});

.toBeArrayOfSize()

Use .toBeArrayOfSize when checking if a value is an Array of size x.

test('passes when value is an array', () => {
  expect([]).toBeArrayOfSize(0);
  expect([1]).toBeArrayOfSize(1);
  expect(true).not.toBeArrayOfSize(1);
});

.toIncludeAllMembers([members])

Use .toIncludeAllMembers when checking if an Array contains all of the same members of a given set.

test('passes when given array values match the members of the set', () => {
  expect([1, 2, 3]).toIncludeAllMembers([2, 1, 3]);
  expect([1, 2, 2]).toIncludeAllMembers([2, 1]);
});

.toIncludeAnyMembers([members])

Use .toIncludeAnyMembers when checking if an Array contains any of the members of a given set.

test('passes when given array values match any of the members in the set', () => {
  expect([1, 2, 3]).toIncludeAnyMembers([2, 1, 3]);
  expect([1, 2, 2]).toIncludeAnyMembers([2]);
  expect([1, 2, 2]).not.toIncludeAnyMembers([3]);
});

.toIncludeSameMembers([members])

Use .toIncludeSameMembers when checking if two arrays contain equal values, in any order.

test('passes when arrays match in a different order', () => {
  expect([1, 2, 3]).toIncludeSameMembers([3, 1, 2]);
  expect([{ foo: 'bar' }, { baz: 'qux' }]).toIncludeSameMembers([{ baz: 'qux' }, { foo: 'bar' }]);
});

.toSatisfyAll(predicate)

Use .toSatisfyAll when you want to use a custom matcher by supplying a predicate function that returns a Boolean for all values in an array.

test('passes when all values in array pass given predicate', () => {
  const isOdd = el => el % 2 === 1;
  expect([1,3,5,7]).toSatisfyAll(isOdd);
  expect([1,3,4,5,7]).not.toSatisfyAll(isOdd);
});

Boolean

.toBeBoolean()

Use .toBeBoolean when checking if a value is a Boolean.

test('passes when value is a boolean', () => {
  expect(false).toBeBoolean();
  expect(true).toBeBoolean();
  expect(1 === 1).toBeBoolean();
  expect(1).not.toBeBoolean();
});

.toBeTrue()

Use .toBeTrue when checking a value is equal (===) to true.

test('is jest cool', () => {
  expect(isJestCool()).toBeTrue();
  expect(false).not.toBeTrue();
});

.toBeFalse()

Use .toBeFalse when checking a value is equal (===) to false.

test('returns false', () => {
  expect(areWeThereYet()).toBeFalse();
  expect(true).not.toBeFalse();
});

Date

Proposal in #117 (under development)

.toBeDate()

Use .toBeDate when checking if a value is a Date.

test('passes when value is a date', () => {
  expect(new Date()).toBeDate();
  expect('01/01/2018').not.toBeDate();
  expect(new Date('01/01/2018').toBeDate();
  expect(undefined).not.toBeDate();
});

.toBeValidDate()

Use .toBeValidDate when checking if a given Date object is valid.

test('passes when Date is valid', () => {
  expect(new Date()).toBeValidDate();
  expect('01/01/2018').not.toBeValidDate();
  expect(new Date('01/01/2018').toBeValidDate();
  expect(new Date('01/90/2018').not.toBeValidDate();
  expect(undefined).not.toBeValidDate();
});

.toBeAfter(date)

Use .toBeAfter when checking if a date occurs after date.

test('passes when input is after date', () => {
 expect(new Date('01/01/2019')).toBeAfter(new Date('01/01/2018'));
 expect('01/01/2018').not.toBeAfter(new Date('01/01/2019'));
});

.toBeBefore(date)

Use .toBeBefore when checking if a date occurs before date.

test('passes when input is before date', () => {
 expect(new Date('01/01/2018')).toBeBefore(new Date('01/01/2019'));
 expect('01/01/2019').not.toBeBefore(new Date('01/01/2018'));
});

Function

.toBeFunction()

Use .toBeFunction when checking if a value is a Function.

test('passes when value is a function', () => {
  function noop = () {};
  expect(() => {}).toBeFunction();
  expect(function() {}).not.toBeFunction();
  expect(noop).toBeFunction();
  expect(true).not.toBeFunction();
});

.toThrowWithMessage(type, message)

Use .toThrowWithMessage when checking if a callback function throws an error with a given error type and given error message. Message can either be a String or a RegExp.

test('throws an error of type TypeError with message "hello world"', () => {
  expect(() => {
    throw TypeError("hello world");
  }).toThrowWithMessage(TypeError, "hello world");

  expect(() => {
    throw TypeError("hello world");
  }).toThrowWithMessage(TypeError, /hello world/);

  expect(() => {
    throw TypeError("hello world 2");
  }).not.toThrowWithMessage(TypeError, "hello world");

  expect(() => {
    throw TypeError("hello world 2");
  }).not.toThrowWithMessage(TypeError, /hello world/);
});

Mock

.toHaveBeenCalledBefore()

Use .toHaveBeenCalledBefore when checking if a Mock was called before another Mock.

Note: Required Jest version >=23

it('calls mock1 before mock2', () => {
  const mock1 = jest.fn();
  const mock2 = jest.fn();

  mock1();
  mock2();
  mock1();

  expect(mock1).toHaveBeenCalledBefore(mock2);
});

.toHaveBeenCalledAfter()

Use .toHaveBeenCalledAfter when checking if a Mock was called after another Mock.

Note: Required Jest version >=23

it('calls mock1 after mock2', () => {
  const mock1 = jest.fn();
  const mock2 = jest.fn();

  mock2();
  mock1();
  mock2();

  expect(mock1).toHaveBeenCalledAfter(mock2);
});

Number

.toBeNumber()

Use .toBeNumber when checking if a value is a Number.

test('passes when value is a number', () => {
  expect(1).toBeNumber();
  expect(NaN).toBeNumber();
  expect(Infinity).toBeNumber();
  expect(true).not.toBeNumber();
});

.toBeNaN()

Use .toBeNaN when checking a value is NaN.

test('passes when value is NaN', () => {
  expect(NaN).toBeNaN();
  expect(1).not.toBeNaN();
});

.toBeFinite()

Use .toBeFinite when checking if a value is a Number, not NaN or Infinity.

test('passes when value is a finite number', () => {
  expect(1).toBeFinite();
  expect(Infinity).not.toBeFinite();
  expect(NaN).not.toBeFinite();
});

.toBePositive()

Use .toBePositive when checking if a value is a positive Number.

test('passes when value is a positive number', () => {
  expect(1).toBePositive();
  expect(Infinity).not.toBePositive();
  expect(-1).not.toBePositive();
  expect(NaN).not.toBePositive();
});

.toBeNegative()

Use .toBeNegative when checking if a value is a negative Number.

test('passes when value is a negative number', () => {
  expect(-1).toBeNegative();
  expect(-Infinity).not.toBeNegative();
  expect(1).not.toBeNegative();
  expect(NaN).not.toBeNegative();
});

.toBeEven()

Use .toBeEven when checking if a value is an even Number.

test('passes when value is an even number', () => {
  expect(2).toBeEven();
  expect(1).not.toBeEven();
  expect(NaN).not.toBeEven();
});

.toBeOdd()

Use .toBeOdd when checking if a value is an odd Number.

test('passes when value is an odd number', () => {
  expect(1).toBeOdd();
  expect(2).not.toBeOdd();
  expect(NaN).not.toBeOdd();
});

.toBeWithin(start, end)

Use .toBeWithin when checking if a number is in between the given bounds of: start (inclusive) and end (exclusive).

test('passes when number is within given bounds', () => {
  expect(1).toBeWithin(1, 3);
  expect(2).toBeWithin(1, 3);
  expect(3).not.toBeWithin(1, 3);
});

Object

.toBeObject()

Use .toBeObject when checking if a value is an Object.

test('passes when value is an object', () => {
  expect({}).toBeObject();
  expect({ a: 'hello' }).toBeObject();
  expect(true).not.toBeObject();
});

.toContainKey(key)

Use .toContainKey when checking if an object contains the provided key.

test('passes when object contains the given key', () => {
  const o = { a: 'foo', b: 'bar', c: 'baz' };
  expect(o).toContainKey('a');
  expect(o).toContainKey('b');
  expect(o).toContainKey('c');
  expect(o).not.toContainKey('d');
});

.toContainKeys([keys])

Use .toContainKeys when checking if an object has all of the provided keys.

test('passes when object contains all keys', () => {
  const o = { a: 'foo', b: 'bar', c: 'baz' };
  expect(o).toContainKeys(['a', 'b']);
  expect(o).toContainKeys(['b', 'c']);
  expect(o).not.toContainKeys(['d']);
});

.toContainAllKeys([keys])

Use .toContainAllKeys when checking if an object only contains all of the provided keys.

test('passes when object only contains all keys', () => {
  const o = { a: 'hello', b: 'world' };
  expect(o).toContainAllKeys(['a', 'b']);
  expect(o).toContainAllKeys(['b', 'a']);
  expect(o).not.toContainAllKeys(['b']);
});

.toContainAnyKeys([keys])

Use .toContainAnyKeys when checking if an object contains at least one of the provided keys.

test('passes when object contains at least one matching key', () => {
  const o = { a: 'hello', b: 'world' };
  expect(o).toContainAnyKeys(['a']);
  expect(o).toContainAnyKeys(['b']);
  expect(o).toContainAnyKeys(['b', 'c']);
  expect(o).not.toContainAnyKeys(['c']);
});

.toContainValue(value)

Use .toContainValue when checking if an object contains the provided value.

test('passes when object contains given value', () => {
  const o = { a: 'foo', b: 'bar', c: 'baz' };
  expect(o).toContainValue('foo');
  expect(o).toContainValue('bar');
  expect(o).not.toContainValue('qux');
});

.toContainValues([values])

Use .toContainValues when checking if an object contains all of the provided values.

test('passes when object contains all of the given values', () => {
  const o = { a: 'foo', b: 'bar', c: 'baz' };
  expect(o).toContainValues(['foo']);
  expect(o).toContainValues(['baz', 'bar']);
  expect(o).not.toContainValues(['qux', 'foo']);
});

.toContainAllValues([values])

Use .toContainAllValues when checking if an object only contains all of the provided values.

test('passes when object only contains all of the given values', () => {
  const o = { a: 'foo', b: 'bar', c: 'baz' };
  expect(o).toContainAllValues(['foo', 'bar', 'baz']);
  expect(o).toContainAllValues(['baz', 'bar', 'foo']);
  expect(o).not.toContainAllValues(['bar', 'foo']);
});

.toContainAnyValues([values])

Use .toContainAnyValues when checking if an object contains at least one of the provided values.

test('passes when object contains at least one of the given values', () => {
  const o = { a: 'foo', b: 'bar', c: 'baz' };
  expect(o).toContainAnyValues(['qux', 'foo']);
  expect(o).toContainAnyValues(['qux', 'bar']);
  expect(o).toContainAnyValues(['qux', 'baz']);
  expect(o).not.toContainAnyValues(['qux']);
});

.toContainEntry([key, value])

Use .toContainEntry when checking if an object contains the provided entry.

test('passes when object contains given entry', () => {
  const o = { a: 'foo', b: 'bar', c: 'baz' };
  expect(o).toContainEntry(['a', 'foo']);
  expect(o).toContainEntry(['b', 'bar']);
  expect(o).toContainEntry(['c', 'baz']);
  expect(o).not.toContainEntry(['a', 'qux']);
});

.toContainEntries([[key, value]])

Use .toContainEntries when checking if an object contains all of the provided entries.

test('passes when object contains all of the given entries', () => {
  const o = { a: 'foo', b: 'bar', c: 'baz' };
  expect(o).toContainEntries([['a', 'foo']]);
  expect(o).toContainEntries([['c', 'baz'], ['a', 'foo']]);
  expect(o).not.toContainEntries([['b', 'qux'], ['a', 'foo']]);
});

.toContainAllEntries([[key, value]])

Use .toContainAllEntries when checking if an object only contains all of the provided entries.

test('passes when object only contains all of the given entries', () => {
  const o = { a: 'foo', b: 'bar', c: 'baz' };
  expect(o).toContainAllEntries([['a', 'foo'], ['b', 'bar'], ['c', 'baz']]);
  expect(o).not.toContainAllEntries([['a', 'foo'], ['b', 'bar']]);
});

.toContainAnyEntries([[key, value]])

Use .toContainAnyEntries when checking if an object contains at least one of the provided entries.

test('passes when object contains at least one of the given entries', () => {
  const o = { a: 'foo', b: 'bar', c: 'baz' };
  expect(o).toContainAnyEntries([['a', 'qux'], ['a', 'foo']]);
  expect(o).toContainAnyEntries([['a', 'qux'], ['b', 'bar']]);
  expect(o).toContainAnyEntries([['a', 'qux'], ['c', 'baz']]);
  expect(o).not.toContainAnyEntries([['d', 'qux']]);
});

.toBeExtensible()

Use .toBeExtensible when checking if an object is extensible.

test('passes when value is extensible', () => {
  expect({a: 1}).toBeExtensible();
  expect(1).not.toBeExtensible();
});

.toBeFrozen()

Use .toBeFrozen when checking if an object is frozen.

test('passes when value is frozen', () => {
  expect(Object.frozen({})).toBeFrozen();
  expect({}).not.toBeFrozen();
  expect(1).not.toBeFrozen();
});

.toBeSealed()

Use .toBeSealed when checking if an object is sealed.

test('passes when value is sealed', () => {
  expect(Object.seal({})).toBeSealed();
  expect({}).not.toBeSealed();
  expect(1).not.toBeSealed();
});

Promise

.toResolve()

Use .toResolve when checking if a promise is resolved.

test('passes when a promise resolves', async () => {
  await expect(Promise.resolve()).toResolve();
});

.toReject()

Use .toReject when checking if a promise is rejected.

test('passes when a promise rejects', async () => {
  await expect(Promise.reject()).toReject();
});

String

.toBeString()

Use .toBeString when checking if a value is a String.

test('passes when value is a string', () => {
  expect('').toBeString();
  expect('hello').toBeString();
  expect(new String('hello')).toBeString();
  expect(true).not.toBeString();
});

.toBeHexadecimal(string)

Use .toBeHexadecimal when checking if a value is a valid HTML hexadecimal color.

test('passes when value is a valid hexadecimal', () => {
  expect('#abc123').toBeHexadecimal();
  expect('#FFF').toBeHexadecimal();
  expect('#000000').toBeHexadecimal();
  expect('#123ffg').not.toBeHexadecimal();
});

.toEqualCaseInsensitive(string)

Use .toEqualCaseInsensitive when checking if a string is equal (===) to another ignoring the casing of both strings.

test('passes when strings are equal ignoring case', () => {
  expect('hello world').toEqualCaseInsensitive('hello world');
  expect('hello WORLD').toEqualCaseInsensitive('HELLO world');
  expect('HELLO WORLD').toEqualCaseInsensitive('hello world');
  expect('hello world').toEqualCaseInsensitive('HELLO WORLD');
  expect('hello world').not.toEqualCaseInsensitive('hello');
});

.toStartWith(prefix)

Use .toStartWith when checking if a String starts with a given String prefix.

test('passes when value is starts with given string', () => {
  expect('hello world').toStartWith('hello');
  expect('hello world').not.toStartWith('world');
});

.toEndWith(suffix)

Use .toEndWith when checking if a String ends with a given String suffix.

test('passes when value is ends with given string', () => {
  expect('hello world').toEndWith('world');
  expect('hello world').not.toEndWith('hello');
});

.toInclude(substring)

Use .toInclude when checking if a String includes the given String substring.

test('passes when value includes substring', () => {
  expect('hello world').toInclude('ell');
  expect('hello world').not.toInclude('bob');
});

.toIncludeRepeated(substring, times)

Use .toIncludeRepeated when checking if a String includes the given String substring the correct number of times.

test('passes when value includes substring n times', () => {
  expect('hello hello world').toIncludeRepeated('hello', 2);
  expect('hello hello world').not.toIncludeRepeated('hello', 1);
});

.toIncludeMultiple([substring])

Use .toIncludeMultiple when checking if a String includes all of the given substrings.

test('passes when value includes all substrings', () => {
  expect('hello world').toIncludeMultiple(['world', 'hello']);
  expect('hello world').not.toIncludeMultiple(['world', 'hello', 'bob']);
});

LICENSE

MIT