docs(react-router): fixes react router v6 examples, removes outdated comments

docs/example-react-router.mdx

@@ -3,12 +3,12 @@ id: example-react-router
 title: React Router
 ---
 
-The example below now supports React Router v6.
+This example demonstrates React Router v6. For previous versions see below.
 
 ```jsx
 // app.js
 import React from 'react'
-import {Link, Route, Switch, useLocation} from 'react-router-dom'
+import {Link, Route, Routes, useLocation} from 'react-router-dom'
 
 const About = () => <div>You are on the about page</div>
 const Home = () => <div>You are home</div>
@@ -26,19 +26,13 @@ export const App = () => (
 
     <Link to="/about">About</Link>
 
-    <Switch>
-      <Route exact path="/">
-        <Home />
-      </Route>
+    <Routes>
+      <Route exact path="/" element={<Home />} />
 
-      <Route path="/about">
-        <About />
-      </Route>
+      <Route path="/about" element={<About />} />
 
-      <Route>
-        <NoMatch />
-      </Route>
-    </Switch>
+      <Route path="*" element={<NoMatch />} />
+    </Routes>
 
     <LocationDisplay />
   </div>
@@ -49,79 +43,55 @@ export const App = () => (
 // app.test.js
 import {render, screen} from '@testing-library/react'
 import userEvent from '@testing-library/user-event'
-import {createMemoryHistory} from 'history'
 import React from 'react'
-import {Router} from 'react-router-dom'
-
 import '@testing-library/jest-dom'
-
 import {App, LocationDisplay} from './app'
+import {BrowserRouter, MemoryRouter} from 'react-router-dom'
 
 test('full app rendering/navigating', async () => {
-  const history = createMemoryHistory()
-  render(
-    <Router location={history.location} navigator={history}>
-      <App />
-    </Router>,
-  )
+  render(<App />, {wrapper: BrowserRouter})
   const user = userEvent.setup()
-  // verify page content for expected route
-  // often you'd use a data-testid or role query, but this is also possible
+
+  // verify page content for default route
   expect(screen.getByText(/you are home/i)).toBeInTheDocument()
 
+  // verify page content for expected route after navigating
   await user.click(screen.getByText(/about/i))
-
-  // check that the content changed to the new page
   expect(screen.getByText(/you are on the about page/i)).toBeInTheDocument()
 })
 
 test('landing on a bad page', () => {
-  const history = createMemoryHistory()
-  history.push('/some/bad/route')
+  const badRoute = '/some/bad/route'
+
+  // use <MemoryRouter> when you want to manually control the history
   render(
-    <Router location={history.location} navigator={history}>
+    <MemoryRouter initialEntries={[badRoute]}>
       <App />
-    </Router>,
+    </MemoryRouter>,
   )
 
+  // verify navigation to "no match" route
   expect(screen.getByText(/no match/i)).toBeInTheDocument()
 })
 
 test('rendering a component that uses useLocation', () => {
-  const history = createMemoryHistory()
   const route = '/some-route'
-  history.push(route)
+
+  // use <MemoryRouter> when you want to manually control the history
   render(
-    <Router location={history.location} navigator={history}>
+    <MemoryRouter initialEntries={[route]}>
       <LocationDisplay />
-    </Router>,
+    </MemoryRouter>,
   )
 
+  // verify location display is rendered
   expect(screen.getByTestId('location-display')).toHaveTextContent(route)
 })
 ```
 
 ## Reducing boilerplate
 
-1. You can use the `wrapper` option to wrap a `MemoryRouter` around the
-   component you want to render.  
-   `MemoryRouter` works when you don't need access to the history object itself
-   in the test, but just need the components to be able to render and
-   navigate.  
-   If you _do_ need to change the history, you could use `BrowserRouter`.
-
-```jsx
-import {MemoryRouter} from 'react-router-dom'
-
-test('full app rendering/navigating', () => {
-  render(<App />, {wrapper: MemoryRouter})
-
-  // verify page content for expected route
-  expect(screen.getByText(/you are home/i)).toBeInTheDocument()
-})
-```
-
-2. If you find yourself adding Router components to your tests a lot, you may
+1. If you find yourself adding Router components to your tests a lot, you may
    want to create a helper function that wraps around `render`.
 
 ```jsx
@@ -161,16 +131,50 @@ test('rendering a component that uses useLocation', () => {
 })
 ```
 
-## Testing Library and React Router v5 
+## Testing Library and React Router v5
 
-In React Router v5, you need to pass the history object as a whole to the Route component.
+In React Router v5, you need to pass the history object as a whole to the Route
+component.
 
 ```jsx
-test('full app rendering/navigating', () => {
+// app.test.js
+import {render, screen} from '@testing-library/react'
+import userEvent from '@testing-library/user-event'
+import {createMemoryHistory} from 'history'
+import React from 'react'
+import {Router} from 'react-router-dom'
+import '@testing-library/jest-dom'
+import {App} from './app'
+
+// React Router v5
+
+test('full app rendering/navigating', async () => {
   const history = createMemoryHistory()
   render(
-    <Router history={history}>
+    <Router location={history.location} navigator={history}>
       <App />
     </Router>,
   )
-  ```
+  const user = userEvent.setup()
+  // verify page content for expected route
+  // often you'd use a data-testid or role query, but this is also possible
+  expect(screen.getByText(/you are home/i)).toBeInTheDocument()
+
+  await user.click(screen.getByText(/about/i))
+
+  // check that the content changed to the new page
+  expect(screen.getByText(/you are on the about page/i)).toBeInTheDocument()
+})
+
+test('landing on a bad page', () => {
+  const history = createMemoryHistory()
+  history.push('/some/bad/route')
+  render(
+    <Router location={history.location} navigator={history}>
+      <App />
+    </Router>,
+  )
+
+  expect(screen.getByText(/no match/i)).toBeInTheDocument()
+})
+```