expect-more-jest

expect-more-jest

Write Beautiful Specs with Custom Matchers for Jest

expect-more-jest is a huge library of test matchers for a range of common use-cases, to make tests easier to read and produce relevant and useful messages when they fail. Avoid vague messages such as "expected false to be true" in favour of useful cues like "expected 3 to be even number", and avoid implementation noise such as expect(paws.length % 2 === 0).toEqual(true) in favour of simply stating that you expect(paws.length).toBeEvenNumber().

Installation

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

Configuration

The simplest way to integrate is to set the setupTestFrameworkScriptFile value of Jest's jest.config.js to require.resolve('expect-more-jest'). If your project requires more setup than just registering these matchers, include require('expect-more-jest'); or import 'expect-more-jest'; somewhere in the file you have pointed your setupTestFrameworkScriptFile at.

Note: If your Editor does not recognise that you are using custom matchers, add a global.d.ts file at the root of your project containing:

import 'expect-more-jest';

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: string).toEndWith(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[])
expect(value: string).toStartWith(other: string)