jest-extended
Advanced tools
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.
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'));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.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 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.
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Additional Jest matchers
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.
jest-extended aims to add additional matchers to Jest's default ones making it easy to test everything š
If you've come here to help contribute - Thanks! Take a look at the contributing docs as a way of getting started.
With npm:
npm install --save-dev jest-extended
With yarn:
yarn add -D jest-extended
Note that jest-extended only supports Jest version 27.2.5 and newer. If you're using an older version of Jest, use 1.2.0.
// ./testSetup.js
// add all jest-extended matchers
import * as matchers from 'jest-extended';
expect.extend(matchers);
// or just add specific matchers
import { toBeArray, toBeSealed } from 'jest-extended';
expect.extend({ toBeArray, toBeSealed });
Add your setup script to your Jest setupFilesAfterEnv configuration. See for help
"jest": {
"setupFilesAfterEnv": ["./testSetup.js"]
}
To automatically extend expect with all matchers, you can use
"jest": {
"setupFilesAfterEnv": ["jest-extended/all"]
}
If your editor does not recognise the custom jest-extended matchers, add a global.d.ts file to your project with:
import 'jest-extended';
Note: When using ts-jest >= 25.5.0
Since the breaking changes in 25.5.0 you may also need to update your tsconfig.json to include the new global.d.ts file in the files property like so:
{
"compilerOptions": {
...
},
...
"files": ["global.d.ts"]
}
Also note that when adding this for the first time this affects which files are compiled by the TypeScript compiler and you might need to add the include property as well. See the TypeScript docs for more details.
If the above import syntax does not work, replace it with the following:
/// <reference types="jest-extended" />
All matchers described in the API are also asymmetrical since jest version 23:
test('passes when using an asymmetrical matcher', () => {
expect([]).toEqual(expect.toBeArray());
});
Passing assertion.
expect().pass('should pass');
Failing assertion.
expect().fail('test should fail');
Use .toBeEmpty when checking if a String '', Array [], Object {}, or Iterable 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();
});
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]);
});
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();
});
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);
});
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();
});
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);
});
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]);
});
Use .toIncludeAllPartialMembers when checking if an Array contains all of the same partial members of a given set.
test('passes when given array values match the partial members of the set', () => {
expect([{ foo: 'bar', baz: 'qux' }]).toIncludeAllPartialMembers([{ foo: 'bar' }]);
});
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]);
});
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' }]);
});
Use .toPartiallyContain when checking if any array value matches the partial member.
test('passes when a string has a given substring', () => {
expect([{ foo: 'bar', baz: 'qux', bax: 'zax' }]).toPartiallyContain({ foo: 'bar' });
expect([{ foo: 'bar', baz: 'qux', bax: 'zax' }]).toPartiallyContain({ baz: 'qux' });
expect([{ foo: 'bar', baz: 'qux', bax: 'zax' }]).not.toPartiallyContain({ foo: 'qux' });
});
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);
});
Use .toSatisfyAny when you want to use a custom matcher by supplying a predicate function that returns true for any matching value in an array.
test('passes when any value in array pass given predicate', () => {
const isOdd = el => el % 2 === 1;
expect([2, 3, 6, 8]).toSatisfyAny(isOdd);
expect([2, 4, 8, 12]).not.toSatisfyAny(isOdd);
});
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();
});
Use .toBeTrue when checking a value is equal (===) to true.
test('is jest cool', () => {
expect(isJestCool()).toBeTrue();
expect(false).not.toBeTrue();
});
Use .toBeFalse when checking a value is equal (===) to false.
test('returns false', () => {
expect(areWeThereYet()).toBeFalse();
expect(true).not.toBeFalse();
});
Proposal in #117 (under development)
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();
});
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();
});
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'));
});
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'));
});
Use .toBeAfterOrEqualTo when checking if a date equals to or occurs after date.
test('passes when input is equal to or after date', () => {
expect(new Date('01/01/2019')).toBeAfterOrEqualTo(new Date('01/01/2018'));
expect(new Date('01/01/2019')).toBeAfterOrEqualTo(new Date('01/01/2019'));
expect('01/01/2018').not.toBeAfterOrEqualTo(new Date('01/01/2019'));
});
Use .toBeBeforeOrEqualTo when checking if a date equals to or occurs before date.
test('passes when input is equal to or before date', () => {
expect(new Date('01/01/2018')).toBeBeforeOrEqualTo(new Date('01/01/2019'));
expect(new Date('01/01/2018')).toBeBeforeOrEqualTo(new Date('01/01/2018'));
expect('01/01/2019').not.toBeBeforeOrEqualTo(new Date('01/01/2018'));
});
Use .toBeBetween when checking if a date equals or occurs after startDate and equals or occurs before endDate.
test('passes when input is in given date range', () => {
expect(new Date('05/01/2019')).toBeBetween(new Date('01/01/2019'), new Date('10/01/2019');
expect(new Date('05/01/2019')).toBeBetween(new Date('05/01/2019'), new Date('10/01/2019');
expect(new Date('01/01/2019')).not.toBeBetween(new Date('05/01/2019'), new Date('10/01/2019'));
});
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();
});
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/);
});
This works for promise rejections too.
test('throws an error of type TypeError with message "hello world"', async () => {
await expect(Promise.reject(new TypeError("hello world async")).rejects.toThrowWithMessage(TypeError, /hello world/);
});
Use .toHaveBeenCalledBefore when checking if a Mock was called before another Mock.
it('calls mock1 before mock2', () => {
const mock1 = jest.fn();
const mock2 = jest.fn();
mock1();
mock2();
mock1();
expect(mock1).toHaveBeenCalledBefore(mock2);
});
Use .toHaveBeenCalledAfter when checking if a Mock was called after another Mock.
it('calls mock1 after mock2', () => {
const mock1 = jest.fn();
const mock2 = jest.fn();
mock2();
mock1();
mock2();
expect(mock1).toHaveBeenCalledAfter(mock2);
});
Use .toHaveBeenCalledOnce to check if a Mock was called exactly one time.
it('passes only if mock was called exactly once', () => {
const mock = jest.fn();
expect(mock).not.toHaveBeenCalled();
mock();
expect(mock).toHaveBeenCalledOnce();
});
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();
});
Use .toBeNaN when checking a value is NaN.
test('passes when value is NaN', () => {
expect(NaN).toBeNaN();
expect(1).not.toBeNaN();
});
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();
});
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();
});
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();
});
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();
});
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();
});
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);
});
Use .toBeInteger when checking if a number is an integer.
test('passes when value is an integer', () => {
expect(1).toBeInteger();
expect(1.0).toBeInteger();
expect(1.1).not.toBeInteger();
});
Use .toBeEmptyObject when checking if a value is an empty Object.
test('passes when value is an empty object', () => {
expect({}).toBeEmptyObject();
expect({ a: 'hello' }).not.toBeEmptyObject();
});
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();
});
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');
});
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']);
});
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']);
});
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']);
});
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');
});
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']);
});
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']);
});
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']);
});
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']);
});
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'],
]);
});
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'],
]);
});
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']]);
});
Use .toBeExtensible when checking if an object is extensible.
test('passes when value is extensible', () => {
expect({ a: 1 }).toBeExtensible();
expect(1).not.toBeExtensible();
});
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();
});
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();
});
Use .toResolve when checking if a promise is resolved.
test('passes when a promise resolves', async () => {
await expect(Promise.resolve()).toResolve();
});
Use .toReject when checking if a promise is rejected.
test('passes when a promise rejects', async () => {
await expect(Promise.reject()).toReject();
});
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();
});
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();
});
Use .toBeDateString when checking if a value is a valid date string.
test('passes when value is a valid toBeDateString', () => {
expect('2019-11-27T14:05:07.520Z').toBeDateString();
expect('11/12/21').toBeDateString();
expect('not a date').not.toBeDateString();
});
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');
});
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');
});
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');
});
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');
});
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);
});
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']);
});
Use .toEqualIgnoringWhitespace when checking if a String is equal to another String ignoring white-space.
test('passes if strings are equal ignoring white-space', () => {
expect('hello world').toEqualIgnoringWhitespace(`
hello
world
`);
expect('SELECT * FROM TABLE WHERE CONDITION').toEqualIgnoringWhitespace(`
SELECT * FROM TABLE
WHERE CONDITION
`);
expect('.class { cssRule: value }').not.toEqualIgnoringWhitespace(`
#id {
cssRule: value
}
`);
});
Use .toBeSymbol when checking if a value is a Symbol.
test('passes when value is a symbol', () => {
expect(Symbol()).toBeSymbol();
expect(true).not.toBeSymbol();
});
FAQs
Additional Jest matchers
The npm package jest-extended receives a total of 753,208 weekly downloads. As such, jest-extended popularity was classified as popular.
We found that jest-extended demonstrated a not healthy version release cadence and project activity because the last version was released a year ago.Ā It has 2 open source maintainers collaborating on the project.
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