feat(matchers): add toHaveAttribute custom matcher (closes #43) (#44)

* Add toHaveAttribute custom matcher

* Add gnapse as contributor

* Generate messages more consistent with jest's other matchers

* Add comment to matcher hint

* Add tests to cover toHaveAttribute custom matcher

.all-contributorsrc

@@ -126,6 +126,17 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "gnapse",
+      "name": "Ernesto García",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/15199?v=4",
+      "profile": "http://gnapse.github.io",
+      "contributions": [
+        "question",
+        "code",
+        "doc"
+      ]
     }
   ]
 }

README.md

@@ -16,7 +16,7 @@
 [![downloads][downloads-badge]][npmtrends]
 [![MIT License][license-badge]][license]
 
-[![All Contributors](https://img.shields.io/badge/all_contributors-12-orange.svg?style=flat-square)](#contributors)
+[![All Contributors](https://img.shields.io/badge/all_contributors-13-orange.svg?style=flat-square)](#contributors)
 [![PRs Welcome][prs-badge]][prs]
 [![Code of Conduct][coc-badge]][coc]
 
@@ -82,7 +82,8 @@ facilitate testing implementation details). Read more about this in
 * [Custom Jest Matchers](#custom-jest-matchers)
   * [`toBeInTheDOM`](#tobeinthedom)
   * [`toHaveTextContent`](#tohavetextcontent)
-  * [Custom Jest Matchers - Typescript](#custom-jest-matchers-typescript)
+  * [`toHaveAttribute`](#tohaveattribute)
+  * [Custom Jest Matchers - Typescript](#custom-jest-matchers---typescript)
 * [`TextMatch`](#textmatch)
 * [`query` APIs](#query-apis)
 * [Examples](#examples)
@@ -138,6 +139,7 @@ test('Fetch makes an API call and displays the greeting when load-greeting is cl
   expect(axiosMock.get).toHaveBeenCalledTimes(1)
   expect(axiosMock.get).toHaveBeenCalledWith(url)
   expect(getByTestId('greeting-text')).toHaveTextContent('hello there')
+  expect(getByTestId('ok-button')).toHaveAttribute('disabled')
   // snapshots work great with regular DOM nodes!
   expect(container.firstChild).toMatchSnapshot()
 })
@@ -347,33 +349,55 @@ expect(getByTestId('count-value')).toHaveTextContent('2')
 expect(getByTestId('count-value')).not.toHaveTextContent('21')
 // ...
 ```
+
+### `toHaveAttribute`
+
+This allows you to check wether the given element has an attribute or not. You
+can also optionally check that the attribute has a specific expected value.
+
+```javascript
+// add the custom expect matchers
+import 'react-testing-library/extend-expect'
+
+// ...
+const {getByTestId} = render(
+  <button data-testid="ok-button" type="submit" disabled>
+    OK
+  </button>,
+)
+expect(getByTestId('ok-button')).toHaveAttribute('disabled')
+expect(getByTestId('ok-button')).toHaveAttribute('type', 'submit')
+expect(getByTestId('ok-button')).not.toHaveAttribute('type', 'button')
+// ...
+```
+
 ### Custom Jest Matchers - Typescript
 
-When you use custom Jest Matchers with Typescript,  you will need to extend the type signature of `jest.Matchers<void>`, then cast the result of `expect` accordingly. Here's a handy usage example:
+When you use custom Jest Matchers with Typescript, you will need to extend the type signature of `jest.Matchers<void>`, then cast the result of `expect` accordingly. Here's a handy usage example:
 
 ```typescript
 // this adds custom expect matchers
-import 'react-testing-library/extend-expect';
+import 'react-testing-library/extend-expect'
 interface ExtendedMatchers extends jest.Matchers<void> {
-  toHaveTextContent: (htmlElement: string) => object;
-  toBeInTheDOM: () => void;
+  toHaveTextContent: (htmlElement: string) => object
+  toBeInTheDOM: () => void
 }
 test('renders the tooltip as expected', async () => {
   const {
     // getByLabelText,
     getByText,
     //  getByTestId,
-    container
-  } = render(<Tooltip label="hello world">Child</Tooltip>);
+    container,
+  } = render(<Tooltip label="hello world">Child</Tooltip>)
   // tests rendering of the child
-  getByText('Child');
+  getByText('Child')
   // tests rendering of tooltip label
-  (expect(getByText('hello world')) as ExtendedMatchers).toHaveTextContent(
-    'hello world'
-  );
+  ;(expect(getByText('hello world')) as ExtendedMatchers).toHaveTextContent(
+    'hello world',
+  )
   // snapshots work great with regular DOM nodes!
-  expect(container.firstChild).toMatchSnapshot();
-});
+  expect(container.firstChild).toMatchSnapshot()
+})
 ```
 
 ## `TextMatch`
@@ -715,10 +739,12 @@ light-weight, simple, and understandable.
 Thanks goes to these people ([emoji key][emojis]):
 
 <!-- ALL-CONTRIBUTORS-LIST:START - Do not remove or modify this section -->
+
 <!-- prettier-ignore -->
 | [<img src="https://avatars.githubusercontent.com/u/1500684?v=3" width="100px;"/><br /><sub><b>Kent C. Dodds</b></sub>](https://kentcdodds.com)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=kentcdodds "Code") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=kentcdodds "Documentation") [🚇](#infra-kentcdodds "Infrastructure (Hosting, Build-Tools, etc)") [⚠️](https://github.com/kentcdodds/react-testing-library/commits?author=kentcdodds "Tests") | [<img src="https://avatars1.githubusercontent.com/u/2430381?v=4" width="100px;"/><br /><sub><b>Ryan Castner</b></sub>](http://audiolion.github.io)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=audiolion "Documentation") | [<img src="https://avatars0.githubusercontent.com/u/8008023?v=4" width="100px;"/><br /><sub><b>Daniel Sandiego</b></sub>](https://www.dnlsandiego.com)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=dnlsandiego "Code") | [<img src="https://avatars2.githubusercontent.com/u/12592677?v=4" width="100px;"/><br /><sub><b>Paweł Mikołajczyk</b></sub>](https://github.com/Miklet)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=Miklet "Code") | [<img src="https://avatars3.githubusercontent.com/u/464978?v=4" width="100px;"/><br /><sub><b>Alejandro Ñáñez Ortiz</b></sub>](http://co.linkedin.com/in/alejandronanez/)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=alejandronanez "Documentation") | [<img src="https://avatars0.githubusercontent.com/u/1402095?v=4" width="100px;"/><br /><sub><b>Matt Parrish</b></sub>](https://github.com/pbomb)<br />[🐛](https://github.com/kentcdodds/react-testing-library/issues?q=author%3Apbomb "Bug reports") [💻](https://github.com/kentcdodds/react-testing-library/commits?author=pbomb "Code") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=pbomb "Documentation") [⚠️](https://github.com/kentcdodds/react-testing-library/commits?author=pbomb "Tests") | [<img src="https://avatars1.githubusercontent.com/u/1288694?v=4" width="100px;"/><br /><sub><b>Justin Hall</b></sub>](https://github.com/wKovacs64)<br />[📦](#platform-wKovacs64 "Packaging/porting to new platform") |
 | :---: | :---: | :---: | :---: | :---: | :---: | :---: |
-| [<img src="https://avatars1.githubusercontent.com/u/1241511?s=460&v=4" width="100px;"/><br /><sub><b>Anto Aravinth</b></sub>](https://github.com/antoaravinth)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=antoaravinth "Code") [⚠️](https://github.com/kentcdodds/react-testing-library/commits?author=antoaravinth "Tests") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=antoaravinth "Documentation") | [<img src="https://avatars2.githubusercontent.com/u/3462296?v=4" width="100px;"/><br /><sub><b>Jonah Moses</b></sub>](https://github.com/JonahMoses)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=JonahMoses "Documentation") | [<img src="https://avatars1.githubusercontent.com/u/4002543?v=4" width="100px;"/><br /><sub><b>Łukasz Gandecki</b></sub>](http://team.thebrain.pro)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=lgandecki "Code") [⚠️](https://github.com/kentcdodds/react-testing-library/commits?author=lgandecki "Tests") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=lgandecki "Documentation") | [<img src="https://avatars2.githubusercontent.com/u/498274?v=4" width="100px;"/><br /><sub><b>Ivan Babak</b></sub>](https://sompylasar.github.io)<br />[🐛](https://github.com/kentcdodds/react-testing-library/issues?q=author%3Asompylasar "Bug reports") [🤔](#ideas-sompylasar "Ideas, Planning, & Feedback") | [<img src="https://avatars3.githubusercontent.com/u/4439618?v=4" width="100px;"/><br /><sub><b>Jesse Day</b></sub>](https://github.com/jday3)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=jday3 "Code") |
+| [<img src="https://avatars1.githubusercontent.com/u/1241511?s=460&v=4" width="100px;"/><br /><sub><b>Anto Aravinth</b></sub>](https://github.com/antoaravinth)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=antoaravinth "Code") [⚠️](https://github.com/kentcdodds/react-testing-library/commits?author=antoaravinth "Tests") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=antoaravinth "Documentation") | [<img src="https://avatars2.githubusercontent.com/u/3462296?v=4" width="100px;"/><br /><sub><b>Jonah Moses</b></sub>](https://github.com/JonahMoses)<br />[📖](https://github.com/kentcdodds/react-testing-library/commits?author=JonahMoses "Documentation") | [<img src="https://avatars1.githubusercontent.com/u/4002543?v=4" width="100px;"/><br /><sub><b>Łukasz Gandecki</b></sub>](http://team.thebrain.pro)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=lgandecki "Code") [⚠️](https://github.com/kentcdodds/react-testing-library/commits?author=lgandecki "Tests") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=lgandecki "Documentation") | [<img src="https://avatars2.githubusercontent.com/u/498274?v=4" width="100px;"/><br /><sub><b>Ivan Babak</b></sub>](https://sompylasar.github.io)<br />[🐛](https://github.com/kentcdodds/react-testing-library/issues?q=author%3Asompylasar "Bug reports") [🤔](#ideas-sompylasar "Ideas, Planning, & Feedback") | [<img src="https://avatars3.githubusercontent.com/u/4439618?v=4" width="100px;"/><br /><sub><b>Jesse Day</b></sub>](https://github.com/jday3)<br />[💻](https://github.com/kentcdodds/react-testing-library/commits?author=jday3 "Code") | [<img src="https://avatars0.githubusercontent.com/u/15199?v=4" width="100px;"/><br /><sub><b>Ernesto García</b></sub>](http://gnapse.github.io)<br />[💬](#question-gnapse "Answering Questions") [💻](https://github.com/kentcdodds/react-testing-library/commits?author=gnapse "Code") [📖](https://github.com/kentcdodds/react-testing-library/commits?author=gnapse "Documentation") |
+
 <!-- ALL-CONTRIBUTORS-LIST:END -->
 
 This project follows the [all-contributors][all-contributors] specification.

src/__tests__/element-queries.js

@@ -117,4 +117,34 @@ test('using jest helpers to assert element states', () => {
   ).toThrowError()
 })
 
+test('using jest helpers to check element attributes', () => {
+  const {queryByTestId} = render(
+    <button data-testid="ok-button" type="submit" disabled>
+      OK
+    </button>,
+  )
+
+  expect(queryByTestId('ok-button')).toHaveAttribute('disabled')
+  expect(queryByTestId('ok-button')).toHaveAttribute('type')
+  expect(queryByTestId('ok-button')).not.toHaveAttribute('class')
+  expect(queryByTestId('ok-button')).toHaveAttribute('type', 'submit')
+  expect(queryByTestId('ok-button')).not.toHaveAttribute('type', 'button')
+
+  expect(() =>
+    expect(queryByTestId('ok-button')).not.toHaveAttribute('disabled'),
+  ).toThrowError()
+  expect(() =>
+    expect(queryByTestId('ok-button')).not.toHaveAttribute('type'),
+  ).toThrowError()
+  expect(() =>
+    expect(queryByTestId('ok-button')).toHaveAttribute('class'),
+  ).toThrowError()
+  expect(() =>
+    expect(queryByTestId('ok-button')).not.toHaveAttribute('type', 'submit'),
+  ).toThrowError()
+  expect(() =>
+    expect(queryByTestId('ok-button')).toHaveAttribute('type', 'button'),
+  ).toThrowError()
+})
+
 /* eslint jsx-a11y/label-has-for:0 */

src/extend-expect.js

@@ -1,4 +1,4 @@
 import extensions from './jest-extensions'
 
-const {toBeInTheDOM, toHaveTextContent} = extensions
-expect.extend({toBeInTheDOM, toHaveTextContent})
+const {toBeInTheDOM, toHaveTextContent, toHaveAttribute} = extensions
+expect.extend({toBeInTheDOM, toHaveTextContent, toHaveAttribute})

src/jest-extensions.js

@@ -1,4 +1,12 @@
-import {matcherHint, printReceived, printExpected} from 'jest-matcher-utils' //eslint-disable-line import/no-extraneous-dependencies
+//eslint-disable-next-line import/no-extraneous-dependencies
+import {
+  matcherHint,
+  printReceived,
+  printExpected,
+  stringify,
+  RECEIVED_COLOR as receivedColor,
+  EXPECTED_COLOR as expectedColor,
+} from 'jest-matcher-utils'
 import {matches} from './utils'
 
 function getDisplayName(subject) {
@@ -9,10 +17,30 @@ function getDisplayName(subject) {
   }
 }
 
+function checkHtmlElement(htmlElement) {
+  if (!(htmlElement instanceof HTMLElement)) {
+    throw new Error(
+      `The given subject is a ${getDisplayName(
+        htmlElement,
+      )}, not an HTMLElement`,
+    )
+  }
+}
+
 const assertMessage = (assertionName, message, received, expected) =>
   `${matcherHint(`${assertionName}`, 'received', '')} \n${message}: ` +
   `${printExpected(expected)} \nReceived: ${printReceived(received)}`
 
+function printAttribute(name, value) {
+  return value === undefined ? name : `${name}=${stringify(value)}`
+}
+
+function getAttributeComment(name, value) {
+  return value === undefined
+    ? `element.hasAttribute(${stringify(name)})`
+    : `element.getAttribute(${stringify(name)}) === ${stringify(value)}`
+}
+
 const extensions = {
   toBeInTheDOM(received) {
     getDisplayName(received)
@@ -42,13 +70,7 @@ const extensions = {
   },
 
   toHaveTextContent(htmlElement, checkWith) {
-    if (!(htmlElement instanceof HTMLElement))
-      throw new Error(
-        `The given subject is a ${getDisplayName(
-          htmlElement,
-        )}, not an HTMLElement`,
-      )
-
+    checkHtmlElement(htmlElement)
     const textContent = htmlElement.textContent
     const pass = matches(textContent, htmlElement, checkWith)
     if (pass) {
@@ -75,6 +97,41 @@ const extensions = {
       }
     }
   },
+
+  toHaveAttribute(htmlElement, name, expectedValue) {
+    checkHtmlElement(htmlElement)
+    const isExpectedValuePresent = expectedValue !== undefined
+    const hasAttribute = htmlElement.hasAttribute(name)
+    const receivedValue = htmlElement.getAttribute(name)
+    return {
+      pass: isExpectedValuePresent
+        ? hasAttribute && receivedValue === expectedValue
+        : hasAttribute,
+      message: () => {
+        const to = this.isNot ? 'not to' : 'to'
+        const receivedAttribute = receivedColor(
+          hasAttribute
+            ? printAttribute(name, receivedValue)
+            : 'attribute was not found',
+        )
+        const expectedMsg = `Expected the element ${to} have attribute:\n  ${expectedColor(
+          printAttribute(name, expectedValue),
+        )}`
+        const matcher = matcherHint(
+          `${this.isNot ? '.not' : ''}.toHaveAttribute`,
+          'element',
+          printExpected(name),
+          {
+            secondArgument: isExpectedValuePresent
+              ? printExpected(expectedValue)
+              : undefined,
+            comment: getAttributeComment(name, expectedValue),
+          },
+        )
+        return `${matcher}\n\n${expectedMsg}\nReceived:\n  ${receivedAttribute}`
+      },
+    }
+  },
 }
 
 export default extensions