update readme with new render API and example

Author: thymikee

README.md

@@ -18,7 +18,28 @@ This library is a replacement for [Enzyme](http://airbnb.io/enzyme/).
 
 ## Example
 
-TBD
+```jsx
+import { render } from 'react-native-testing-library';
+import { QuestionsBoard } from '../QuestionsBoard';
+
+function setAnswer(getAllByName, index, answer) {
+  getAllByName('Question')[index].props.onChangeText(answer);
+}
+
+test('should verify two questions', () => {
+  const { getAllByName, getByText } = render(<QuestionsBoard {...props} />);
+
+  setAnswer(getAllByName, 0, 'a1');
+  setAnswer(getAllByName, 1, 'a2');
+
+  getByText('submit').props.onPress();
+
+  expect(props.verifyQuestions).toBeCalledWith({
+    '1': { q: 'q1', a: 'a1' },
+    '2': { q: 'q2', a: 'a2' },
+  });
+});
+```
 
 ## Installation
 
@@ -28,20 +49,83 @@ Open a Terminal in your project's folder and run:
 yarn add --dev react-testing-library
 ```
 
-This library has a peerDependencies listing for `react-test-renderer` and, of course, `react`.
+This library has a peerDependencies listing for `react-test-renderer` and, of course, `react`. Make sure to install them too!
+
+As you may have noticed, it's not tied to React Native at all – you can safely use it in your React components if you feel like not interacting directly with DOM.
 
 ## Usage
 
 ## `render`
 
-Deeply render given React component and returns helpers to query the output. For convenience it also returns `react-test-renderer`'s `instance` and `renderer` objects, in case you need more control.
+Defined as:
+
+```jsx
+function render(
+  component: React.Element<*>,
+  options?: {
+    /* You won't often use this, but it's helpful when testing refs */
+    createNodeMock: (element: React.Element<*>) => any,
+  }
+): RenderResult {}
+```
+
+Deeply render given React element and returns helpers to query the output. For convenience it also returns `react-test-renderer`'s `instance` and `renderer` objects, in case you need more control.
 
 ```jsx
 import { render } from 'react-native-testing-library';
 
-const { getByTestId, instance /*...*/ } = render(<Component />);
+const { getByTestId, getByName /*...*/ } = render(<Component />);
 ```
 
+Returns a `RenderResult` object with following properties:
+
+### `getByTestId: (testID: string)`
+
+A method returning a `ReactTestInstance` with matching `testID` prop. Throws when no matches.
+
+_Note: most methods like this one return a [`ReactTestInstance`](https://reactjs.org/docs/test-renderer.html#testinstance) with following properties that you may be interested in:_
+
+```jsx
+type ReactTestInstance = {
+  type: string | Function,
+  props: { [propName: string]: any },
+  parent: null | ReactTestInstance,
+  children: Array<ReactTestInstance | string>,
+};
+```
+
+### `getByName: (name: string | React.Element<*>)`
+
+A method returning a `ReactTestInstance` with matching name – may be a string or React Element. Throws when no matches.
+
+### `getAllByName: (name: string | React.Element<*>)`
+
+A method returning an array of `ReactTestInstance`s with matching name – may be a string or React Element.
+
+### `getByText: (text: string | RegExp)`
+
+A method returning a `ReactTestInstance` with matching text – may be a string or regular expression. Throws when no matches.
+
+### `getAllByText: (text: string | RegExp)`
+
+A method returning an array of `ReactTestInstance`s with matching text – may be a string or regular expression.
+
+### `getByProps: (props: { [propName: string]: any })`
+
+A method returning a `ReactTestInstance` with matching props object. Throws when no matches.
+
+### `getAllByProps: (props: { [propName: string]: any })`
+
+A method returning an array of `ReactTestInstance`s with matching props object.
+
+### `update: (element: React.Element<*>) => void`
+
+Re-render the in-memory tree with a new root element. This simulates a React update at the root. If the new element has the same type and key as the previous element, the tree will be updated; otherwise, it will re-mount a new tree.
+
+### `unmount: () => void`
+
+Unmount the in-memory tree, triggering the appropriate lifecycle events
+
 When using React context providers, like Redux Provider, you'll likely want to wrap rendered component with them. In such cases it's convenient to create your custom `render` method. [Follow this great guide on how to set this up](https://github.com/kentcdodds/react-testing-library#custom-render).
 
 ## `shallow`