expect-more-jest

Write Beautiful Specs with Custom Matchers for Jest

What

A huge library of test matchers a range of common use-cases.

Why

Custom Matchers make tests easier to read and produce relevant and useful messages when they fail.

How

By avoiding vague messages such as "expected false to be true" in favour of useful cues such as "expected 3 to be even number" and avoiding implementation noise such as expect(paws.length % 2 === 0).toEqual(true) in favour of simply stating that you expect(paws.length).toBeEvenNumber().

Status

expect-more-jest is a recent TypeScript rewrite of jasmine-expect . Most effort is required on documentation and any contributions in this area would be really welcome.

Installation

npm install expect-more-jest --save-dev

Setup

The simplest way to integrate is to include the following in your jest.config.js:

module.exports = {
  // ...
  setupTestFrameworkScriptFile: require.resolve('expect-more-jest')
  // ...
};

If your project requires more setup than just these matchers, point your setupTestFrameworkScriptFile entry to a JavaScript file somewhere in your project like so:

module.exports = {
  // ...
  setupTestFrameworkScriptFile: '<rootDir>/test/setup-test-framework-script-file.js'
  // ...
};

In that file (in this example we have chosen ./test/setup-test-framework-script-file.js) include:

import 'expect-more-jest';
// ...then your other setup code

or:

require('expect-more-jest');
// ...then your other setup code

API

Asymmetric Matchers

• expect.after(date: Date)
• expect.arrayOfBooleans()
• expect.arrayOfNumbers()
• expect.arrayOfObjects()
• expect.arrayOfSize(size: number)
• expect.arrayOfStrings()
• expect.before(date: Date)
• expect.calculable()
• expect.divisibleBy(other: number)
• expect.endingWith(other: string)
• expect.evenNumber()
• expect.iso8601()
• expect.jsonString()
• expect.longerThan(other: string | any[])
• expect.near(other: number, epsilon: number)
• expect.nonEmptyArray()
• expect.nonEmptyObject()
• expect.nonEmptyString()
• expect.oddNumber()
• expect.sameLengthAs(other: string | any[])
• expect.shorterThan(other: string | any[])
• expect.startingWith(other: string)
• expect.validDate()
• expect.whitespace()
• expect.wholeNumber()
• expect.withinRange(floor: number, ceiling: number)

Matchers

• expect(date: Date).toBeAfter(other: Date)
• expect(value).toBeArray()
• expect(value).toBeArrayOfBooleans()
• expect(value).toBeArrayOfNumbers()
• expect(value).toBeArrayOfObjects()
• expect(value).toBeArrayOfSize(size: number)
• expect(value).toBeArrayOfStrings()
• expect(date: Date).toBeBefore(other: Date)
• expect(value).toBeBoolean()
• expect(value).toBeCalculable()
• expect(value).toBeDate()
• expect(value).toBeDivisibleBy(other: number)
• expect(value).toBeEmptyArray()
• expect(value).toBeEmptyObject()
• expect(value).toBeEmptyString()
• expect(value).toBeEvenNumber()
• expect(value).toBeFalse()
• expect(value).toBeFunction()
• expect(value).toBeIso8601()
• expect(value).toBeJsonString()
• expect(value: string | any[]).toBeLongerThan(other: string | any[])
• expect(value).toBeNonEmptyArray()
• expect(value).toBeNonEmptyObject()
• expect(value).toBeNonEmptyString()
• expect(value).toBeNumber()
• expect(value).toBeObject()
• expect(value).toBeOddNumber()
• expect(value).toBeRegExp()
• expect(value: string | any[]).toBeSameLengthAs(other: string | any[])
• expect(value: string | any[]).toBeShorterThan(other: string | any[])
• expect(value).toBeString()
• expect(value).toBeTrue()
• expect(value).toBeValidDate()
• expect(value).toBeWhitespace()
• expect(value).toBeWholeNumber()
• expect(value).toBeWithinRange()
• expect(value: string).toEndWith(other: string)
• expect(value: string).toStartWith(other: string)
• expect(fn).toHandleMissingBranches(shape: object | any[])
• expect(fn).toHandleMissingLeaves(shape: object | any[])
• expect(fn).toHandleMissingNodes(shape: object | any[])
• expect(fn).toHandleNullBranches(shape: object | any[])
• expect(fn).toHandleNullLeaves(shape: object | any[])
• expect(fn).toHandleNullNodes(shape: object | any[])