refactoring asFragment example to use hooks (testing-library#193)

Author: pedroapfilho

docs/react-testing-library/api.md

@@ -226,23 +226,17 @@ Returns a `DocumentFragment` of your rendered component. This can be useful if
 you need to avoid live bindings and see how your component reacts to events.
 
 ```jsx
+import React, { useState } from 'react'
 import { render, fireEvent } from '@testing-library/react'
 
-class TestComponent extends React.Component {
- constructor() {
- super()
- this.state = { count: 0 }
- }
-
- render() {
- const { count } = this.state
+const TestComponent = () => {
+ const [count, setCounter] = useState(0)
 
- return (
- <button onClick={() => this.setState({ count: count + 1 })}>
- Click to increase: {count}
- </button>
- )
- }
+ return (
+ <button onClick={() => setCounter(count => count + 1)}>
+ Click to increase: {count}
+ </button>
+ )
 }
 
 const { getByText, asFragment } = render(<TestComponent />)