API
@testing-library/dom
This library re-exports everything from the DOM Testing Library
(@testing-library/dom
). See the
documentation to see what goodies you
can use.
render
import { render } from '@testing-library/preact'
const { results } = render(<YourComponent />, { options })
Options
Option | Description | Default |
---|---|---|
container | The HTML element the component is mounted to. | baseElement |
baseElement | The root HTML element to which the container is appended to. | document.body |
queries | Queries to bind to the baseElement. See getQueriesForElement. | null |
hydrate | Used when the component has already been mounted and requires a rerender. Not needed for most people. The rerender function passed back to you does this already. | false |
wrapper | A parent component to wrap YourComponent. | null |
Results
Result | Description |
---|---|
container | The HTML element the component is mounted to. |
baseElement | The root HTML element to which the container is appended to. |
debug | Logs the baseElement using prettyDom. |
unmount | Unmounts the component from the container. |
rerender | Calls render again passing in the original arguments and sets hydrate to true. |
asFragment | Returns the innerHTML of the container. |
...queries | Returns all query functions to be used on the baseElement. If you pass in query arguments than this will be those, otherwise all. |
cleanup
Unmounts the component from the container and destroys the container.
๐ When you import anything from the library, this automatically runs after each
test. If you'd like to disable this then set process.env.PTL_SKIP_AUTO_CLEANUP
to true when running your tests.
import { render, cleanup } from '@testing-library/preact'
afterEach(() => {
cleanup()
}) // Default on import: runs it after each test.
render(<YourComponent />)
cleanup() // Or like this for more control.
act
Just a convenience export that points to preact/test-utils/act. All renders and
events being fired are wrapped in act
, so you don't really need this. It's
responsible for flushing all effects and rerenders after invoking it.
๐ If you'd love to learn more, checkout this explanation. Even thought it's for React, it gives you an idea of why it's needed.
fireEvent
Passes it to the @testing-library/dom
fireEvent. It's also wrapped in act
so
you don't need to worry about doing it.
๐ Keep in mind mainly when using h / Preact.createElement
that React uses a
Synthetic event system, and Preact uses the browser's native addEventListener
for event handling. This means events like onChange
and onDoubleClick
in
React, are onInput
and onDblClick
in Preact. The double click example will
give you an idea of how to test using those functions.
Example 1
const cb = jest.fn();
function Counter() {
useEffect(cb);
const [count, setCount] = useState(0);
return <button onClick={() => setCount(count + 1)}>{count}</button>;
}
const { container: { firstChild: buttonNode }, } = render(<Counter />);
// Clear the first call to useEffect that the initial render triggers.
cb.mockClear();
// Fire event Option 1.
fireEvent.click(buttonNode);
// Fire event Option 2.
fireEvent(
buttonNode,
new Event('MouseEvent', {
bubbles: true,
cancelable: true,
button: 0,
});
expect(buttonNode).toHaveTextContent('1');
expect(cb).toHaveBeenCalledTimes(1);
Example 2
const handler = jest.fn()
const {
container: { firstChild: input },
} = render(<input type="text" onInput={handler} />)
fireEvent.input(input, { target: { value: 'a' } })
expect(handler).toHaveBeenCalledTimes(1)
Example 3
const ref = createRef()
const spy = jest.fn()
render(
h(elementType, {
onDblClick: spy,
ref,
})
)
fireEvent['onDblClick'](ref.current)
expect(spy).toHaveBeenCalledTimes(1)