preact-hooks-testing-library


preact port of the the @testing-library/react-hooks library.

Why not @testing-library/react-hooks?

Currently, due to the use of react-test-renderer, the react hooks testing library most likely will never be compatible with preact.

Why not another library?

At the time of writing, a library did not exist to test preact hooks.

When to use this library

1. You're writing a library with one or more custom hooks that are not directly tied to a component
2. You have a complex hook that is difficult to test through component interactions

When not to use this library

1. Your hook is defined alongside a component and is only used there
2. Your hook is easy to test by just testing the components using it

Installation

Install with your favorite package manager

``
yarn add -D @testing-library/preact-hooks
OR
npm install --save-dev @testing-library/preact-hooks
`

Example #1: Basic

`typescript
import { useState, useCallback } from 'preact/hooks';

const useCounter = () => {
const [count, setCount] = useState(0);

const increment = useCallback(() => setCount(c => c + 1));

return {
count,
increment
}
}

export default useCounter;
`

$3

`typescript
import { renderHook, act } from '@testing-library/preact-hooks';
import useCounter from './useCounter';

test('should increment counter', () => {
const { result } = renderHook(() => useCounter());

act(() => {
result.current.increment();
});

expect(result.current.count).toBe(1);
});

`

Example #2: Wrapped Components

Sometimes, hooks may need access to values or functionality outside of itself that are provided by a context provider or some other HOC.

`typescript jsx
import { createContext } from 'preact'
import { useState, useCallback, useContext } from 'preact/hooks'

const CounterStepContext = createContext(1)
export const CounterStepProvider = ({ step, children }) => (
{children}
)
export function useCounter(initialValue = 0) {
const [count, setCount] = useState(initialValue)
const step = useContext(CounterStepContext)
const increment = useCallback(() => setCount((x) => x + step), [step])
const reset = useCallback(() => setCount(initialValue), [initialValue])
return { count, increment, reset }
}

`

In our test, we simply use CoounterStepProvider as the wrapper when rendering the hook:

`typescript
import { renderHook, act } from '@testing-library/preact-hooks'
import { CounterStepProvider, useCounter } from './counter'

test('should use custom step when incrementing', () => {
const wrapper = ({ children }) => {children}
const { result } = renderHook(() => useCounter(), { wrapper })
act(() => {
result.current.increment()
})
expect(result.current.count).toBe(2)
})
`

$3

- [ ] remove @ts-nocheck` flag from tests
- [ ] fix disabled auto clean up tests