You want to use jest to write tests that assert various things about the state of a DOM. As part of that goal, you want to avoid all the repetitive patterns that arise in doing so. Checking for an element's attributes, its text content, its css classes, you name it.
The jest-dom library provides a set of custom jest matchers that you can use
to extend jest. These will make your tests more declarative, clear to read and
to maintain.
- Installation
- Usage
- Custom matchers
- Deprecated matchers
- Inspiration
- Other Solutions
- Guiding Principles
- Contributors
- LICENSE
This module is distributed via npm which is bundled with node and
should be installed as one of your project's devDependencies:
npm install --save-dev jest-dom
Import jest-dom/extend-expect once (for instance in your tests setup file)
and you're good to go:
import 'jest-dom/extend-expect'Alternatively, you can selectively import only the matchers you intend to use,
and extend jest's expect yourself:
import {toBeInTheDocument, toHaveClass} from 'jest-dom'
expect.extend({toBeInTheDocument, toHaveClass})Note: when using TypeScript, this way of importing matchers won't provide the necessary type definitions. More on this here.
toBeEmpty()This allows you to assert whether an element has content or not.
// add the custom expect matchers once
import 'jest-dom/extend-expect'
// ...
// <span data-testid="not-empty"><span data-testid="empty"></span></span>
expect(queryByTestId(container, 'empty')).toBeEmpty()
expect(queryByTestId(container, 'not-empty')).not.toBeEmpty()
// ...toBeInTheDocument()This allows you to assert whether an element is present in the document or not.
// add the custom expect matchers once
import 'jest-dom/extend-expect'
// ...
// document.body.innerHTML = `<span data-testid="html-element"><span>Html Element</span></span><svg data-testid="svg-element"></svg>`
// const htmlElement = document.querySelector('[data-testid="html-element"]')
// const svgElement = document.querySelector('[data-testid="svg-element"]')
// const detachedElement = document.createElement('div')
expect(htmlElement).toBeInTheDocument()
expect(svgElement).toBeInTheDocument()
expect(detacthedElement).not.toBeInTheDocument()
// ...Note: This will not find detached elements. The element must be added to the document to be found. If you desire to search in a detached element please use:
toContainElement
toContainElement(element: HTMLElement | SVGElement)This allows you to assert whether an element contains another element as a descendant or not.
// add the custom expect matchers once
import 'jest-dom/extend-expect'
// ...
// <span data-testid="ancestor"><span data-testid="descendant"></span></span>
const ancestor = queryByTestId(container, 'ancestor')
const descendant = queryByTestId(container, 'descendant')
expect(ancestor).toContainElement(descendant)
expect(descendant).not.toContainElement(ancestor)
// ...toHaveTextContent(text: string | RegExp)This API allows you to check whether the given element has a text content or not.
// add the custom expect matchers once
import 'jest-dom/extend-expect'
// ...
// <span data-testid="count-value">2</span>
expect(getByTestId(container, 'count-value')).toHaveTextContent('2')
expect(getByTestId(container, 'count-value')).not.toHaveTextContent('21')
// ...toHaveAttribute(attr: string, value?: string)This allows you to check whether the given element has an attribute or not. You can also optionally check that the attribute has a specific expected value.
// add the custom expect matchers once
import 'jest-dom/extend-expect'
// ...
// <button data-testid="ok-button" type="submit" disabled>
// OK
// </button>
expect(getByTestId(container, 'ok-button')).toHaveAttribute('disabled')
expect(getByTestId(container, 'ok-button')).toHaveAttribute('type', 'submit')
expect(getByTestId(container, 'ok-button')).not.toHaveAttribute(
'type',
'button',
)
// ...toHaveClass(...classNames: string[])This allows you to check whether the given element has certain classes within its
class attribute.
// add the custom expect matchers once
import 'jest-dom/extend-expect'
// ...
// <button data-testid="delete-button" class="btn extra btn-danger">
// Delete item
// </button>
expect(getByTestId(container, 'delete-button')).toHaveClass('extra')
expect(getByTestId(container, 'delete-button')).toHaveClass('btn-danger btn')
expect(getByTestId(container, 'delete-button')).toHaveClass('btn-danger', 'btn')
expect(getByTestId(container, 'delete-button')).not.toHaveClass('btn-link')
// ...You must provide at least one class, unless you are asserting that an element does not have any classes.
// ...
// <button data-testid="no-classes">
// Delete item
// </button>
expect(getByTestId(container, 'no-classes')).not.toHaveClass()toHaveStyle(css: string)This allows you to check if a certain element has some specific css properties with specific values applied. It matches only if the element has all the expected properties applied, not just some of them.
// add the custom expect matchers once
import 'jest-dom/extend-expect'
// ...
// <button data-testid="delete-button" style="display: none; color: red">
// Delete item
// </button>
expect(getByTestId(container, 'delete-button')).toHaveStyle('display: none')
expect(getByTestId(container, 'delete-button')).toHaveStyle(`
color: red;
display: none;
`)
expect(getByTestId(container, 'delete-button')).not.toHaveStyle(`
display: none;
color: blue;
`)
// ...This also works with rules that are applied to the element via a class name for which some rules are defined in a stylesheet currently active in the document. The usual rules of css precedence apply.
toHaveFocus()This allows you to assert whether an element has focus or not.
// add the custom expect matchers once
import 'jest-dom/extend-expect'
// ...
// <div><input id="focused" type="text" data-testid="focused" /></div>
// const { container } = render(...)
// const input = container.querySelector('#focused');
// input.focus()
expect(queryByTestId(container, 'focused')).toHaveFocus()
// input.blur()
expect(queryByTestId(container, 'focused')).not.toHaveFocus()
// ...toBeVisible()This allows you to check if an element is currently visible to the user.
An element is visible if all the following conditions are met:
- it does not have its css property
displayset tonone - it does not have its css property
visibilityset to eitherhiddenorcollapse - it does not have its css property
opacityset to0 - its parent element is also visible (and so on up to the top of the DOM tree)
// add the custom expect matchers once
import 'jest-dom/extend-expect'
// ...
// <header>
// <h1 style="display: none">Page title</h1>
// </header>
// <section>
// <p style="visibility: hidden">Hello <strong>World</strong></h1>
// </section>
expect(container.querySelector('header')).toBeVisible()
expect(container.querySelector('h1')).not.toBeVisible()
expect(container.querySelector('strong')).not.toBeVisible()
// ...toBeDisabled()This allows you to check whether an element is disabled from the user's perspective.
It matches if the element is a form control and the disabled attribute is
specified on this element or the element is a descendant of a form element
with a disabled attribute.
According to the specification, the following elements can be actually disabled:
button, input, select, textarea, optgroup, option, fieldset.
// add the custom expect matchers once
import 'jest-dom/extend-expect'
// ...
// <button data-testid="button" type="submit" disabled>
// SUBMIT
// </button>
// <fieldset disabled>
// <input type="text" data-testid="text" />
// </fieldset>
expect(getByTestId(container, 'button')).toBeDisabled()
expect(getByTestId(container, 'text')).toBeDisabled()
// ...
// ...
// <a href="..." disabled>LINK</a>
expect(getByText(container, 'LINK')).not.toBeDisabled()
// ...toBeInTheDOM()This allows you to check whether a value is a DOM element, or not.
Contrary to what its name implies, this matcher only checks that you passed to it a valid DOM element. It does not have a clear definition of that "the DOM" is. Therefore, it does not check wether that element is contained anywhere.
This is the main reason why this matcher is deprecated, and will be removed in the next major release. You can follow the discussion around this decision in more detail here.
As an alternative, you can use toBeInTheDocument
or toContainElement. Or if you just want to check if a
value is indeed an HTMLElement you can always use some of
jest's built-in matchers:
expect(document.querySelector('.ok-button')).toBeInstanceOf(HTMLElement)
expect(document.querySelector('.cancel-button')).toBeThruthy();Note: The differences between
toBeInTheDOMandtoBeInTheDocumentare significant. Replacing all uses oftoBeInTheDOMwithtoBeInTheDocumentwill likely cause unintended consequences in your tests. Please make sure when replacingtoBeInTheDOMto read through the documentation of the proposed alternatives to see which use case works better for your needs.
This whole library was extracted out of Kent C. Dodds' dom-testing-library, which was in turn extracted out of react-testing-library.
The intention is to make this available to be used independently of these other libraries, and also to make it more clear that these other libraries are independent from jest, and can be used with other tests runners as well.
I'm not aware of any, if you are please make a pull request and add it here!
The more your tests resemble the way your software is used, the more confidence they can give you.
This library follows the same guiding principles as its mother library dom-testing-library. Go check them out for more details.
Additionally, with respect to custom DOM matchers, this library aims to maintain a minimal but useful set of them, while avoiding bloating itself with merely convenient ones that can be easily achieved with other APIs. In general, the overall criteria for what is considered a useful custom matcher to add to this library, is that doing the equivalent assertion on our own makes the test code more verbose, less clear in its intent, and/or harder to read.
Thanks goes to these people (emoji key):
This project follows the all-contributors specification. Contributions of any kind welcome!
MIT