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Excerpt
Note
Note
Most projects have a few use cases for
fireEvent
, but the majority of the time you should probably use [@testing-library/user-event
](https: //testing-library.com/docs/ecosystem-user-event).
fireEvent
Fire DOM events.
fireEvent[eventName]
Convenience methods for firing DOM events. Check out [src/event-map.js](https: //github.com/testing-library/dom-testing-library/blob/master/src/event-map.js) for a full list as well as default eventProperties
.
target: When an event is dispatched on an element, the event has the subjected element on a property called target
. As a convenience, if you provide a target
property in the eventProperties
(second argument), then those properties will be assigned to the node which is receiving the event.
This is particularly useful for a change event:
dataTransfer: Drag events have a dataTransfer
property that contains data transferred during the operation. As a convenience, if you provide a dataTransfer
property in the eventProperties
(second argument), then those properties will be added to the event.
This should predominantly be used for testing drag and drop interactions.
Keyboard events: There are three event types related to keyboard input - keyPress
, keyDown
, and keyUp
. When firing these you need to reference an element in the DOM and the key you want to fire.
You can find out which key code to use at [https: //keycode.info/](https: //keycode.info).
createEvent[eventName]
Convenience methods for creating DOM events that can then be fired by fireEvent
, allowing you to have a reference to the event created: this might be useful if you need to access event properties that cannot be initiated programmatically (such as timeStamp
).
You can also create generic events:
[Jest's Mock functions](https: //jestjs.io/docs/en/mock-functions) can be used to test that a callback passed to the function was called, or what it was called when the event that should trigger the callback function does trigger the bound callback.
React
Excerpt
Overview
Queries are the methods that Testing Library gives you to find elements on the page. There are several types of queries ("get", "find", "query"); the difference between them is whether the query will throw an error if no element is found or if it will return a Promise and retry. Depending on what page content you are selecting, different queries may be more or less appropriate. See the priority guide for recommendations on how to make use of semantic queries to test your page in the most accessible way.
After selecting an element, you can use the Events API or user-event to fire events and simulate user interactions with the page, or use Jest and jest-dom to make assertions about the element.
There are Testing Library helper methods that work with queries. As elements appear and disappear in response to actions, Async APIs like waitFor
or findBy
queries can be used to await the changes in the DOM. To find only elements that are children of a specific element, you can use within
. If necessary, there are also a few options you can configure, like the timeout for retries and the default testID attribute.
Single Elements
getBy...
: Returns the matching node for a query, and throw a descriptive error if no elements match or if more than one match is found (use getAllBy
instead if more than one element is expected).
queryBy...
: Returns the matching node for a query, and return null
if no elements match. This is useful for asserting an element that is not present. Throws an error if more than one match is found (use queryAllBy
instead if this is OK).
findBy...
: Returns a Promise which resolves when an element is found which matches the given query. The promise is rejected if no element is found or if more than one element is found after a default timeout of 1000ms. If you need to find more than one element, use findAllBy
.
Multiple Elements
getAllBy...
: Returns an array of all matching nodes for a query, and throws an error if no elements match.
queryAllBy...
: Returns an array of all matching nodes for a query, and return an empty array ([]
) if no elements match.
findAllBy...
: Returns a promise which resolves to an array of elements when any elements are found which match the given query. The promise is rejected if no elements are found after a default timeout of 1000
ms.
findBy
methods are a combination of getBy*
queries and waitFor
. They accept the waitFor
options as the last argument (i.e. await screen.findByText('text', queryOptions, waitForOptions)
)
Summary Table
Based on the Guiding Principles, your test should resemble how users interact with your code (component, page, etc.) as much as possible. With this in mind, we recommend this order of priority:
Queries Accessible to Everyone Queries that reflect the experience of visual/mouse users as well as those that use assistive technology.
getByRole
: This can be used to query every element that is exposed in the accessibility tree. With the name
option you can filter the returned elements by their accessible name. This should be your top preference for just about everything. There's not much you can't get with this (if you can't, it's possible your UI is inaccessible). Most often, this will be used with the name
option like so: getByRole('button', {name: /submit/i})
. Check the list of roles.
getByLabelText
: This method is really good for form fields. When navigating through a website form, users find elements using label text. This method emulates that behavior, so it should be your top preference.
getByPlaceholderText
: A placeholder is not a substitute for a label. But if that's all you have, then it's better than alternatives.
getByText
: Outside of forms, text content is the main way users find elements. This method can be used to find non-interactive elements (like divs, spans, and paragraphs).
getByDisplayValue
: The current value of a form element can be useful when navigating a page with filled-in values.
Semantic Queries HTML5 and ARIA compliant selectors. Note that the user experience of interacting with these attributes varies greatly across browsers and assistive technology.
getByAltText
: If your element is one which supports alt
text (img
, area
, input
, and any custom element), then you can use this to find that element.
getByTitle
: The title attribute is not consistently read by screenreaders, and is not visible by default for sighted users
Test IDs
getByTestId
: The user cannot see (or hear) these, so this is only recommended for cases where you can't match by role or text or it doesn't make sense (e.g. the text is dynamic).
The base queries from DOM Testing Library require you to pass a container
as the first argument. Most framework-implementations of Testing Library provide a pre-bound version of these queries when you render your components with them which means you do not have to provide a container. In addition, if you just want to query document.body
then you can use the screen
export as demonstrated below (using screen
is recommended).
The primary argument to a query can be a string, regular expression, or function. There are also options to adjust how node text is parsed. See TextMatch for documentation on what can be passed to a query.
Given the following DOM elements (which can be rendered by React, Vue, Angular, or plain HTML code):
You can use a query to find an element (byLabelText, in this case):
screen
All of the queries exported by DOM Testing Library accept a container
as the first argument. Because querying the entire document.body
is very common, DOM Testing Library also exports a screen
object which has every query that is pre-bound to document.body
(using the within
functionality). Wrappers such as React Testing Library re-export screen
so you can use it the same way.
Here's how you use it:
Native
React
Cypress
Note
You need a global DOM environment to use
screen
. If you're using jest, with the testEnvironment set tojsdom
, a global DOM environment will be available for you.If you're loading your test with a
script
tag, make sure it comes after thebody
. An example can be seen here.
TextMatch
Most of the query APIs take a TextMatch
as an argument, which means the argument can be either a string, regex, or a function which returns true
for a match and false
for a mismatch.
Given the following HTML:
Will** find the div:**
Will not** find the div:**
Queries that take a TextMatch
also accept an object as the final argument that can contain options that affect the precision of string matching:
exact
: Defaults to true
; matches full strings, case-sensitive. When false, matches substrings and is not case-sensitive.
exact
has no effect on regex
or function
arguments.
In most cases using a regex instead of a string gives you more control over fuzzy matching and should be preferred over { exact: false }
.
normalizer
: An optional function which overrides normalization behavior. See Normalization
.
Before running any matching logic against text in the DOM, DOM Testing Library
automatically normalizes that text. By default, normalization consists of trimming whitespace from the start and end of text, and collapsing multiple adjacent whitespace characters into a single space.
If you want to prevent that normalization, or provide alternative normalization (e.g. to remove Unicode control characters), you can provide a normalizer
function in the options object. This function will be given a string and is expected to return a normalized version of that string.
Note
Specifying a value for
normalizer
replaces the built-in normalization, but you can callgetDefaultNormalizer
to obtain a built-in normalizer, either to adjust that normalization or to call it from your own normalizer.
getDefaultNormalizer
takes an options object which allows the selection of behaviour:
trim
: Defaults to true
. Trims leading and trailing whitespace
collapseWhitespace
: Defaults to true
. Collapses inner whitespace (newlines, tabs, repeated spaces) into a single space.
Normalization Examples
To perform a match against text without trimming:
To override normalization to remove some Unicode characters whilst keeping some (but not all) of the built-in normalization behavior:
screen.debug()
For convenience screen also exposes a debug
method in addition to the queries. This method is essentially a shortcut for console.log(prettyDOM())
. It supports debugging the document, a single element, or an array of elements.
screen.logTestingPlaygroundURL()
For debugging using testing-playground, screen exposes this convenient method which logs a URL that can be opened in a browser.
On top of the queries provided by the testing library, you can use the regular querySelector
DOM API to query elements. Note that using this as an escape hatch to query by class or id is not recommended because they are invisible to the user. Use a testid if you have to, to make your intention to fall back to non-semantic queries clear and establish a stable API contract in the HTML.
Do you still have problems knowing how to use Testing Library queries?
There is a very cool Browser extension for Chrome and Firefox named Testing Playground, and it helps you find the best queries to select elements. It allows you to inspect the element hierarchies in the Browser's Developer Tools, and provides you with suggestions on how to select them, while encouraging good testing practices.
If you want to get more familiar with these queries, you can try them out on testing-playground.com. Testing Playground is an interactive sandbox where you can run different queries against your own html, and get visual feedback matching the rules mentioned above.
Type of Query | 0 Matches | 1 Match | >1 Matches | Retry (Async/Await) |
---|---|---|---|---|
Single Element
getBy...
Throw error
Return element
Throw error
No
queryBy...
Return null
Return element
Throw error
No
findBy...
Throw error
Return element
Throw error
Yes
Multiple Elements
getAllBy...
Throw error
Return array
Return array
No
queryAllBy...
Return []
Return array
Return array
No
findAllBy...
Throw error
Return array
Return array
Yes