Add render count

.all-contributorsrc

@@ -120,6 +120,17 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "Belco90",
+      "name": "Mario Beltrán",
+      "avatar_url": "https://avatars1.githubusercontent.com/u/2677072?v=4",
+      "profile": "https://mario.dev",
+      "contributions": [
+        "code",
+        "doc",
+        "test"
+      ]
     }
   ],
   "commitConvention": "none"

README.md

@@ -27,7 +27,7 @@
 [![downloads](https://img.shields.io/npm/dm/@testing-library/react-hooks.svg?style=flat-square)](http://www.npmtrends.com/@testing-library/react-hooks)
 [![MIT License](https://img.shields.io/npm/l/@testing-library/react-hooks.svg?style=flat-square)](https://github.com/testing-library/react-hooks-testing-library/blob/master/LICENSE.md)
 
-[![All Contributors](https://img.shields.io/badge/all_contributors-11-orange.svg?style=flat-square)](#contributors)
+[![All Contributors](https://img.shields.io/badge/all_contributors-12-orange.svg?style=flat-square)](#contributors-)
 [![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg?style=flat-square)](http://makeapullrequest.com)
 [![Code of Conduct](https://img.shields.io/badge/code%20of-conduct-ff69b4.svg?style=flat-square)](https://github.com/testing-library/react-hooks-testing-library/blob/master/CODE_OF_CONDUCT.md)
 [![Netlify Status](https://api.netlify.com/api/v1/badges/9a8f27a5-df38-4910-a248-4908b1ba29a7/deploy-status)](https://app.netlify.com/sites/react-hooks-testing-library/deploys)
@@ -142,7 +142,8 @@ See the [API documentation](https://react-hooks-testing-library.com/reference/ap
 Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/docs/en/emoji-key)):
 
 <!-- ALL-CONTRIBUTORS-LIST:START - Do not remove or modify this section -->
-<!-- prettier-ignore -->
+<!-- prettier-ignore-start -->
+<!-- markdownlint-disable -->
 <table>
   <tr>
     <td align="center"><a href="https://github.com/mpeyper"><img src="https://avatars0.githubusercontent.com/u/23029903?v=4" width="100px;" alt="Michael Peyper"/><br /><sub><b>Michael Peyper</b></sub></a><br /><a href="https://github.com/testing-library/react-hooks-testing-library/commits?author=mpeyper" title="Code">💻</a> <a href="#design-mpeyper" title="Design">🎨</a> <a href="https://github.com/testing-library/react-hooks-testing-library/commits?author=mpeyper" title="Documentation">📖</a> <a href="#ideas-mpeyper" title="Ideas, Planning, & Feedback">🤔</a> <a href="#infra-mpeyper" title="Infrastructure (Hosting, Build-Tools, etc)">🚇</a> <a href="#platform-mpeyper" title="Packaging/porting to new platform">📦</a> <a href="https://github.com/testing-library/react-hooks-testing-library/commits?author=mpeyper" title="Tests">⚠️</a> <a href="#tool-mpeyper" title="Tools">🔧</a></td>
@@ -158,9 +159,13 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
     <td align="center"><a href="https://github.com/mtinner"><img src="https://avatars0.githubusercontent.com/u/5487448?v=4" width="100px;" alt="Marcel Tinner"/><br /><sub><b>Marcel Tinner</b></sub></a><br /><a href="https://github.com/testing-library/react-hooks-testing-library/commits?author=mtinner" title="Documentation">📖</a></td>
     <td align="center"><a href="https://github.com/FredyC"><img src="https://avatars0.githubusercontent.com/u/1096340?v=4" width="100px;" alt="Daniel K."/><br /><sub><b>Daniel K.</b></sub></a><br /><a href="https://github.com/testing-library/react-hooks-testing-library/issues?q=author%3AFredyC" title="Bug reports">🐛</a> <a href="https://github.com/testing-library/react-hooks-testing-library/commits?author=FredyC" title="Code">💻</a></td>
     <td align="center"><a href="https://github.com/VinceMalone"><img src="https://avatars0.githubusercontent.com/u/2516349?v=4" width="100px;" alt="Vince Malone"/><br /><sub><b>Vince Malone</b></sub></a><br /><a href="https://github.com/testing-library/react-hooks-testing-library/commits?author=VinceMalone" title="Code">💻</a></td>
+    <td align="center"><a href="https://mario.dev"><img src="https://avatars1.githubusercontent.com/u/2677072?v=4" width="100px;" alt="Mario Beltrán"/><br /><sub><b>Mario Beltrán</b></sub></a><br /><a href="https://github.com/testing-library/react-hooks-testing-library/commits?author=Belco90" title="Code">💻</a> <a href="https://github.com/testing-library/react-hooks-testing-library/commits?author=Belco90" title="Documentation">📖</a> <a href="https://github.com/testing-library/react-hooks-testing-library/commits?author=Belco90" title="Tests">⚠️</a></td>
   </tr>
 </table>
 
+<!-- markdownlint-enable -->
+<!-- prettier-ignore-end -->
+
 <!-- ALL-CONTRIBUTORS-LIST:END -->
 
 This project follows the [all-contributors](https://allcontributors.org/) specification.

docs/reference/api.md

@@ -62,12 +62,14 @@ The `renderHook` method returns an object that has a following properties:
 ```js
 {
   current: any,
-  error: Error
+  error: Error,
+  renderCount: number
 }
 ```
 
 The `current` value or the `result` will reflect whatever is returned from the `callback` passed to
-`renderHook`. Any thrown values will be reflected in the `error` value of the `result`.
+`renderHook`. Any thrown values will be reflected in the `error` value of the `result`. Within
+`renderCount` it's possible to know how many times the component was rendered.
 
 ### `waitForNextUpdate`
 

docs/usage/basic-hooks.md

@@ -221,3 +221,25 @@ test("should clean up side effect", () => {
 ```
 
 This is a fairly obscure case, so pick the method that fits best for you and your test.
+
+## Knowing how many times component was rendered
+
+It's also possible to know how many times the component containing the tested hook was rendered
+under `renderCount` property within result.
+
+```js
+import { renderHook, act } from '@testing-library/react-hooks'
+import { useState } from 'react'
+
+test('should rerender component on each update', () => {
+  const { result } = renderHook(() => useState('foo'))
+  const [, setState] = result.current
+  expect(result.renderCount).toBe(1)
+
+  act(() => {
+    setState('bar')
+  })
+
+  expect(result.renderCount).toBe(2)
+})
+```

src/index.js

@@ -21,6 +21,7 @@ function Fallback() {
 function resultContainer() {
   let value = null
   let error = null
+  let renderCount = 0
   const resolvers = []
 
   const result = {
@@ -32,10 +33,14 @@ function resultContainer() {
     },
     get error() {
       return error
+    },
+    get renderCount() {
+      return renderCount
     }
   }
 
   const updateResult = (val, err) => {
+    renderCount++
     value = val
     error = err
     resolvers.splice(0, resolvers.length).forEach((resolve) => resolve())

test/updateHook.test.js

@@ -0,0 +1,34 @@
+import { useState } from 'react'
+import { renderHook, act } from 'src'
+
+describe('update hook tests', () => {
+  function useUpdate() {
+    const [, setState] = useState(0)
+    return () => setState((count) => count + 1)
+  }
+
+  test('should increase render count every time hook update function is called', () => {
+    const { result } = renderHook(() => useUpdate())
+    const update = result.current
+
+    expect(result.renderCount).toBe(1)
+
+    act(() => update())
+    expect(result.renderCount).toBe(2)
+
+    act(() => update())
+    expect(result.renderCount).toBe(3)
+  })
+
+  test('should increase render count every time rerender function is called', () => {
+    const { result, rerender } = renderHook(() => useUpdate())
+
+    expect(result.renderCount).toBe(1)
+
+    rerender()
+    expect(result.renderCount).toBe(2)
+
+    rerender()
+    expect(result.renderCount).toBe(3)
+  })
+})

typings/index.d.ts

@@ -9,6 +9,7 @@ export interface RenderHookOptions<P> {
 export interface HookResult<R> {
   readonly current: R
   readonly error: Error
+  readonly renderCount: number
 }
 
 export interface RenderHookResult<P, R> {