add MatchGroup tests

closes #3936, #3994, #4032

be sure to see commit messages on cf2555d

Author: ryanflorence

modules/__tests__/MatchGroup-test.js

@@ -0,0 +1,51 @@
+import expect from 'expect'
+import React from 'react'
+import { render, unmountComponentAtNode } from 'react-dom'
+import Match from '../Match'
+import Miss from '../Miss'
+import MatchGroup from '../MatchGroup'
+import Router from '../MemoryRouter'
+
+describe('MatchGroup', () => {
+  const div = document.createElement('div')
+
+  const HOME = 'HOME'
+  const Home = () => <div>{HOME}</div>
+
+  const FOO = 'FOO'
+  const Foo = () => <div>{FOO}</div>
+
+  const NO_MATCH = 'NO_MATCH'
+  const NoMatch = () => <div>{NO_MATCH}</div>
+
+  const App = ({ pathname }) => (
+    <Router initialEntries={[{ pathname }]}>
+      <MatchGroup>
+        <Match exactly pattern="/" component={Home} />
+        <Match pattern="/foo" component={Foo} />
+        <Miss component={NoMatch} />
+      </MatchGroup>
+    </Router>
+  )
+
+  afterEach(() => unmountComponentAtNode(div))
+
+  it('renders the first matching child', () => {
+    render(<App pathname="/"/>, div, () => {
+      expect(div.innerHTML).toContain(HOME)
+    })
+  })
+
+  it('renders the first matching child that is not the first child', () => {
+    render(<App pathname="/foo"/>, div, () => {
+      expect(div.innerHTML).toContain(FOO)
+    })
+  })
+
+  it('renders a miss when nothing else matches', () => {
+    render(<App pathname="/no-match"/>, div, () => {
+      expect(div.innerHTML).toContain(NO_MATCH)
+    })
+  })
+})
+