jest-test-performance

Purpose

jest-test-performance is a package designed to simplify testing performance.

Performance is notoriously difficult to test in a meaningful way. It varies by network, machine, and all sorts of circumstances outside our control. And it's affected by our psychology; a page that loads something quickly feels faster even if it is just a skeleton of how the page will look.

That doesn't change the fact that performance is meaningful, and we shouldn't disregard it because it's difficult.

This package distills performance down to a single millisecond score that it expects a function to take to run. It can't take in to account every machine, browser, or network, but it provides a baseline based on an average machine, that we can test against.

I would recommend using this more in integration than unit tests, unless you are confident that you have a distinct unit that is a bottleneck.

Installation

Add to your project using npm i -D jest-test-performance

Usage

First you need to import the package during the jest setup.

"jest": {
  "setupFilesAfterEnv": ["jest-test-performance"]
}

And then you can use the condition during assertions.

it('should run faster than 100ms', async () => {
  const dummyFunction = () => {};
  await expect(dummyFunction).toBeFasterThan(100);
});