jest-matchers

Some additional Jest matchers I usually use in my projects.

Usage

• Install dependency:

  npm install --dev @kayahr/jest-matchers

• Import it in your Jest test file:

  @import "@kayahr/jest-matchers";

Matchers

toEqualCloseTo(value, numDigits?)

Recursive version of toBeCloseTo() so you can compare arrays or objects with numeric values with a specific precision. numDigits defaults to 2 if not specified.

expect(values).toEqualCloseTo([ 10.3132, 40.1224, 50.1311 ], 4);

toBeEquatable(equalValues, unequalValues)

Checks if the tested object has an equals method which correctly implements an equivalence relation on non-null object references (See Java's object.equals() method for details).

expect(new Color(0, 0, 0)).toBeEquatable(
    [ new Color(0, 0, 0), new Color("black") ],
    [ new Color(1, 0, 0), new Color(0, 1, 0), new Color(0, 0, 1), new Color("white") ]
);

toBeGarbageCollected(destructor, timeout)

Checks if the test object (which must be passed via a WeakRef) is correctly garbage collected. For this you have to specify a destructor function which removes all references to the test object. You can also optionally specify a timeout which defaults to 5000 milliseconds. When the object was not garbage collected in this time then the test fails.

let testSubject: Record<string, unknown> | undefined = { a: 34 };
await expect(new WeakRef(testSubject)).toBeGarbageCollected(() => { testSubject = undefined; });