getByRole("progressbar") is pretty slow

• React Testing Library version: 10.0.4 (I’m using /react not /dom but I’m posting here as getByRole is implemented here)
• node version: 🤷 (codesandbox)
• npm (or yarn) version: 🤷 (codesandbox)

I’ve noticed that some of my tests were pretty slow to run (more than 2 seconds). After investigating, I’ve noticed that the following pattern was to source of the slowness:

await waitForElementToBeRemoved(() => screen.getByRole('progressbar'))

If I add a data-testid to my loader and switch to:

await waitForElementToBeRemoved(() => screen.getByTestId('loader'))

it’s much faster.

Relevant code or config:

I’m sometimes displayed a CircularProgress from material-ui while fetching some data and I use this pattern to wait for it to be removed.

await waitForElementToBeRemoved(() => screen.getByRole('progressbar'))

example of implementation

if(isLoading) {
  return <CircularProgress className={classes.loader} data-testid="loader" />
}

What happened:

Here are 2 tests outputs where I only change the pattern mentioned above.

getByRole

getByTestId:

Reproduction:

I’ve create the following Sandbox: https://codesandbox.io/s/musing-gauss-e1ynf?file=/src/Demo.js

The numbers are much smaller but when running the tests several times we can see that the getByRole is slower when used on the CircularProgress.

Problem description:

I think that

await waitForElementToBeRemoved(() => screen.getByRole('progressbar'))

is the best pattern to test that a loader is displayed on screen. However, the slowness prevents us from using in all our tests as it quickly gets slow.

[eps1lon]

getByRole can get quite expensive in large trees since it currently checks every element while ByTestId is a simple querySelector. It also includes a lot more a11y related checks. For example it won’t return inaccessible elements.

Since you actually remove the element from the DOM you can ignore the additional a11y tree checks and go with getByRole('progressbar', { hidden: false }).

On slow machines these additional checks can starve your CPU and you should increase the polling interval with waitForElementToBeRemoved(() => {}, { interval: 200 }) (try out which interval works best).

And last but not least: What version of jest or, more specifically, jsdom are you using? In later jsdom versions (or actual browsers) getByRole should be a lot faster.

For us: I think we should make the perf impact of hidden in ByRole clearer in the docs. Also mention too low polling rate on slow machines.

[atsikov]

For those who use styled-components a lot, such wrapper could improve getByRole performance by leaving only a few css rules used by @testing-library and thus significantly reducing <style> size

import { ReactNode } from 'react'
import { StyleSheetManager, StylisPlugin } from 'styled-components'

const ALLOWED_RULES = ['display', 'visibility', 'pointer-events']

const simplifiedStylesPlugin: StylisPlugin = (context, content) => {
  if (context === 1) {
    if (!ALLOWED_RULES.some(rule => content.toString().startsWith(`${rule}:`))) {
      return ''
    }
  }

  return undefined
}

export const withSimplifiedStyles = (component: ReactNode) => (
  <StyleSheetManager stylisPlugins={[simplifiedStylesPlugin]} disableVendorPrefixes>
    {component}
  </StyleSheetManager>
)