Fix up custom render + rerender samples

The get/query methods in the "how to override data-testid" sample
were not `.bind`ing correctly; I've replaced them with arrow functions
as suggested.  They were also passing in `container`, which wasn't
correct. Also, a `rerender` implementation is needed in such a
custom renderer, so I've added one to the sample.

I've also fixed up the separate custom rerender sample as it a)
incorrectly advertised an options parameter, and b) didn't pass
along the original baseElement.

For: #225

Author: RoystonS

.all-contributorsrc

@@ -595,6 +595,17 @@
       "contributions": [
         "doc"
       ]
+    },
+    {
+      "login": "RoystonS",
+      "name": "Royston Shufflebotham",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/19773?v=4",
+      "profile": "https://github.com/RoystonS",
+      "contributions": [
+        "bug",
+        "doc",
+        "example"
+      ]
     }
   ]
 }

README.md

@@ -11,16 +11,23 @@
 <hr />
 
 [![Build Status][build-badge]][build]
+
 [![Code Coverage][coverage-badge]][coverage]
+
 [![version][version-badge]][package] [![downloads][downloads-badge]][npmtrends]
+
 [![MIT License][license-badge]][license]
 
-[![All Contributors](https://img.shields.io/badge/all_contributors-61-orange.svg?style=flat-square)](#contributors)
+[![All Contributors](https://img.shields.io/badge/all_contributors-62-orange.svg?style=flat-square)](#contributors)
+
 [![PRs Welcome][prs-badge]][prs] [![Code of Conduct][coc-badge]][coc]
+
 [![Join the community on Spectrum][spectrum-badge]][spectrum]
 
 [![Watch on GitHub][github-watch-badge]][github-watch]
+
 [![Star on GitHub][github-star-badge]][github-star]
+
 [![Tweet][twitter-badge]][twitter]
 
 <div align="center">
@@ -82,6 +89,7 @@ facilitate testing implementation details). Read more about this in
 ## What is react-testing-library?
 
 Have a look at the video below for an explanation. <br/><br/>
+
 [![what is react testing library](https://img.youtube.com/vi/JKOwJUM4_RM/0.jpg)](https://youtu.be/JKOwJUM4_RM 'what is react testing library')
 
 ## Example
@@ -317,12 +325,15 @@ return value of the customRender.
 ```js
 // test-utils.js
 
-const customRender = (node, options) => {
-  const rendered = render(<div>{node}</div>, options)
+const customRender = (ui, options) => {
+  const rendered = render(<div>{ui}</div>, options)
   return {
     ...rendered,
-    rerender: (ui, options) =>
-      customRender(ui, {container: rendered.container, ...options}),
+    rerender: newUi =>
+      customRender(newUi, {
+        container: rendered.container,
+        baseElement: rendered.baseElement,
+      }),
   }
 }
 ```
@@ -621,24 +632,22 @@ change. This follows the precedent set by
 which uses a `testID` prop which emits a `data-testid` attribute on the element.
 
 [#76](https://github.com/kentcdodds/dom-testing-library/issues/76#issuecomment-406321122)
+
 [#128](https://github.com/kentcdodds/dom-testing-library/issues/128)
+
 [#204](https://github.com/kentcdodds/react-testing-library/issues/204).
 
 What you can do is to create a [custom render](#custom-render) that overwrites
-`getByTestId`:
+`getByTestId` and related methods, and also `rerender`:
 
 ```js
 // test-utils.js
 import {render, queryHelpers} from 'react-testing-library'
 
-export const queryByTestId = queryHelpers.queryByAttribute.bind(
-  null,
-  'data-test-id',
-)
-export const queryAllByTestId = queryHelpers.queryAllByAttribute.bind(
-  null,
-  'data-test-id',
-)
+export const queryByTestId = (...rest) =>
+  queryHelpers.queryByAttribute('data-test-id', ...rest)
+export const queryAllByTestId = (...rest) =>
+  queryHelpers.queryAllByAttribute('data-test-id', ...rest)
 
 export function getAllByTestId(container, id, ...rest) {
   const els = queryAllByTestId(container, id, ...rest)
@@ -651,19 +660,25 @@ export function getAllByTestId(container, id, ...rest) {
   return els
 }
 
-export function getByTestId(...args) {
-  return queryHelpers.firstResultOrNull(getAllByTestId, ...args)
-}
+export const getByTestId = (...rest) =>
+  queryHelpers.firstResultOrNull(getAllByTestId, ...rest)
 
-const customRender = (container, options) => {
-  const utils = render(container, options)
+const customRender = (ui, options) => {
+  const rendered = render(ui, options)
 
   return {
-    ...utils,
-    getByTestId: getByTestId.bind(container),
-    getAllByTestId: getAllByTestId.bind(container),
-    queryByTestId: queryByTestId.bind(container),
-    queryAllByTestId: queryAllByTestId.bind(container),
+    ...rendered,
+    getByTestId: (...rest) => getByTestId(rendered.container, ...rest),
+    getAllByTestId: (...rest) => getAllByTestId(rendered.container, ...rest),
+    queryByTestId: (...rest) => queryByTestId(rendered.container, ...rest),
+    queryAllByTestId: (...rest) =>
+      queryAllByTestId(rendered.container, ...rest),
+
+    rerender: newUi =>
+      customRender(newUi, {
+        container: rendered.container,
+        baseElement: rendered.baseElement,
+      }),
   }
 }
 
@@ -1336,6 +1351,7 @@ inspired by and mostly compatible with this library.
 In preparing this project,
 [I tweeted about it](https://twitter.com/kentcdodds/status/974278185540964352)
 and [Sune Simonsen](https://github.com/sunesimonsen)
+
 [took up the challenge](https://twitter.com/sunesimonsen/status/974784783908818944).
 We had different ideas of what to include in the library, so I decided to create
 this one instead.
@@ -1378,7 +1394,7 @@ Thanks goes to these people ([emoji key][emojis]):
 | [<img src="https://avatars2.githubusercontent.com/u/5286559?v=4" width="100px;"/><br /><sub><b>Mark Pollmann</b></sub>](https://markpollmann.com/)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=MarkPollmann "Documentation") | [<img src="https://avatars1.githubusercontent.com/u/1213123?v=4" width="100px;"/><br /><sub><b>Ehtesham Kafeel</b></sub>](https://github.com/ehteshamkafeel)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=ehteshamkafeel "Code") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=ehteshamkafeel "Documentation") | [<img src="https://avatars2.githubusercontent.com/u/1493505?v=4" width="100px;"/><br /><sub><b>Julio Pavón</b></sub>](http://jpavon.com)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=jpavon "Code") | [<img src="https://avatars3.githubusercontent.com/u/1765048?v=4" width="100px;"/><br /><sub><b>Duncan L</b></sub>](http://www.duncanleung.com/)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=duncanleung "Documentation") [💡](#example-duncanleung "Examples") | [<img src="https://avatars1.githubusercontent.com/u/700778?v=4" width="100px;"/><br /><sub><b>Tiago Almeida</b></sub>](https://www.linkedin.com/in/tyagow/?locale=en_US)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=tyagow "Documentation") | [<img src="https://avatars2.githubusercontent.com/u/4982001?v=4" width="100px;"/><br /><sub><b>Robert Smith</b></sub>](http://rbrtsmith.com/)<br />[🐛](https://github.com/kentcdodds/react-testing-library/issues?q=author%3Arbrtsmith "Bug reports") | [<img src="https://avatars0.githubusercontent.com/u/1700355?v=4" width="100px;"/><br /><sub><b>Zach Green</b></sub>](https://offbyone.tech)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=zgreen "Documentation") |
 | [<img src="https://avatars3.githubusercontent.com/u/881986?v=4" width="100px;"/><br /><sub><b>dadamssg</b></sub>](https://github.com/dadamssg)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=dadamssg "Documentation") | [<img src="https://avatars0.githubusercontent.com/u/8734097?v=4" width="100px;"/><br /><sub><b>Yazan Aabed</b></sub>](https://www.yaabed.com/)<br />[📝](#blog-YazanAabeed "Blogposts") | [<img src="https://avatars0.githubusercontent.com/u/556258?v=4" width="100px;"/><br /><sub><b>Tim</b></sub>](https://github.com/timbonicus)<br />[🐛](https://github.com/kentcdodds/react-testing-library/issues?q=author%3Atimbonicus "Bug reports") [💻](https://github.com/kentcdodds/react-testing-library/commits?author=timbonicus "Code") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=timbonicus "Documentation") [⚠️](https://github.com/kentcdodds/react-testing-library/commits?author=timbonicus "Tests") | [<img src="https://avatars3.githubusercontent.com/u/6682655?v=4" width="100px;"/><br /><sub><b>Divyanshu Maithani</b></sub>](http://divyanshu.xyz)<br />[✅](#tutorial-divyanshu013 "Tutorials") [📹](#video-divyanshu013 "Videos") | [<img src="https://avatars2.githubusercontent.com/u/9116042?v=4" width="100px;"/><br /><sub><b>Deepak Grover</b></sub>](https://www.linkedin.com/in/metagrover)<br />[✅](#tutorial-metagrover "Tutorials") [📹](#video-metagrover "Videos") | [<img src="https://avatars0.githubusercontent.com/u/16276358?v=4" width="100px;"/><br /><sub><b>Eyal Cohen</b></sub>](https://github.com/eyalcohen4)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=eyalcohen4 "Documentation") | [<img src="https://avatars3.githubusercontent.com/u/7452681?v=4" width="100px;"/><br /><sub><b>Peter Makowski</b></sub>](https://github.com/petermakowski)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=petermakowski "Documentation") |
 | [<img src="https://avatars2.githubusercontent.com/u/20361668?v=4" width="100px;"/><br /><sub><b>Michiel Nuyts</b></sub>](https://github.com/Michielnuyts)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=Michielnuyts "Documentation") | [<img src="https://avatars0.githubusercontent.com/u/1195863?v=4" width="100px;"/><br /><sub><b>Joe Ng'ethe</b></sub>](https://github.com/joeynimu)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=joeynimu "Code") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=joeynimu "Documentation") | [<img src="https://avatars3.githubusercontent.com/u/19998290?v=4" width="100px;"/><br /><sub><b>Kate</b></sub>](https://github.com/Enikol)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=Enikol "Documentation") | [<img src="https://avatars1.githubusercontent.com/u/11980217?v=4" width="100px;"/><br /><sub><b>Sean</b></sub>](http://www.seanrparker.com)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=SeanRParker "Documentation") | [<img src="https://avatars2.githubusercontent.com/u/17031?v=4" width="100px;"/><br /><sub><b>James Long</b></sub>](http://jlongster.com)<br />[🤔](#ideas-jlongster "Ideas, Planning, & Feedback") [📦](#platform-jlongster "Packaging/porting to new platform") | [<img src="https://avatars1.githubusercontent.com/u/10118777?v=4" width="100px;"/><br /><sub><b>Herb Hagely</b></sub>](https://github.com/hhagely)<br />[💡](#example-hhagely "Examples") | [<img src="https://avatars2.githubusercontent.com/u/5779538?v=4" width="100px;"/><br /><sub><b>Alex Wendte</b></sub>](http://www.wendtedesigns.com/)<br />[💡](#example-themostcolm "Examples") |
-| [<img src="https://avatars0.githubusercontent.com/u/6998954?v=4" width="100px;"/><br /><sub><b>Monica Powell</b></sub>](http://www.aboutmonica.com)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=M0nica "Documentation") | [<img src="https://avatars1.githubusercontent.com/u/2699953?v=4" width="100px;"/><br /><sub><b>Vitaly Sivkov</b></sub>](http://sivkoff.com)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=sivkoff "Code") | [<img src="https://avatars3.githubusercontent.com/u/7049?v=4" width="100px;"/><br /><sub><b>Weyert de Boer</b></sub>](https://github.com/weyert)<br />[🤔](#ideas-weyert "Ideas, Planning, & Feedback") [👀](#review-weyert "Reviewed Pull Requests") | [<img src="https://avatars3.githubusercontent.com/u/13613037?v=4" width="100px;"/><br /><sub><b>EstebanMarin</b></sub>](https://github.com/EstebanMarin)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=EstebanMarin "Documentation") | [<img src="https://avatars2.githubusercontent.com/u/13953703?v=4" width="100px;"/><br /><sub><b>Victor Martins</b></sub>](https://github.com/vctormb)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=vctormb "Documentation") |
+| [<img src="https://avatars0.githubusercontent.com/u/6998954?v=4" width="100px;"/><br /><sub><b>Monica Powell</b></sub>](http://www.aboutmonica.com)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=M0nica "Documentation") | [<img src="https://avatars1.githubusercontent.com/u/2699953?v=4" width="100px;"/><br /><sub><b>Vitaly Sivkov</b></sub>](http://sivkoff.com)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=sivkoff "Code") | [<img src="https://avatars3.githubusercontent.com/u/7049?v=4" width="100px;"/><br /><sub><b>Weyert de Boer</b></sub>](https://github.com/weyert)<br />[🤔](#ideas-weyert "Ideas, Planning, & Feedback") [👀](#review-weyert "Reviewed Pull Requests") | [<img src="https://avatars3.githubusercontent.com/u/13613037?v=4" width="100px;"/><br /><sub><b>EstebanMarin</b></sub>](https://github.com/EstebanMarin)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=EstebanMarin "Documentation") | [<img src="https://avatars2.githubusercontent.com/u/13953703?v=4" width="100px;"/><br /><sub><b>Victor Martins</b></sub>](https://github.com/vctormb)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=vctormb "Documentation") | [<img src="https://avatars0.githubusercontent.com/u/19773?v=4" width="100px;"/><br /><sub><b>Royston Shufflebotham</b></sub>](https://github.com/RoystonS)<br />[🐛](https://github.com/kentcdodds/react-testing-library/issues?q=author%3ARoystonS "Bug reports") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=RoystonS "Documentation") [💡](#example-RoystonS "Examples") |
 
 <!-- ALL-CONTRIBUTORS-LIST:END -->