feat(cleanup): automatically cleanup if afterEach is detected

You can disable this with the RTL_SKIP_CLEANUP environment variable if
you so choose, but it's recommended to have cleanup work this way.

Closes #428

Author: Kent C. Dodds

src/__tests__/auto-cleanup-skip.js

@@ -0,0 +1,18 @@
+import React from 'react'
+
+let render
+beforeAll(() => {
+  process.env.RTL_SKIP_CLEANUP = 'true'
+  const rtl = require('../')
+  render = rtl.render
+})
+
+// This one verifies that if RTL_SKIP_CLEANUP is set
+// that we DON'T auto-wire up the afterEach for folks
+test('first', () => {
+  render(<div>hi</div>)
+})
+
+test('second', () => {
+  expect(document.body.innerHTML).toEqual('<div><div>hi</div></div>')
+})

src/__tests__/auto-cleanup.js

@@ -0,0 +1,13 @@
+import React from 'react'
+import {render} from '../'
+
+// This just verifies that by importing RTL in an
+// environment which supports afterEach (like jest)
+// we'll get automatic cleanup between tests.
+test('first', () => {
+  render(<div>hi</div>)
+})
+
+test('second', () => {
+  expect(document.body.innerHTML).toEqual('')
+})

src/index.js

@@ -142,6 +142,16 @@ fireEvent.select = (node, init) => {
   fireEvent.keyUp(node, init)
 }
 
+// if we're running in a test runner that supports afterEach
+// then we'll automatically run cleanup afterEach test
+// this ensures that tests run in isolation from each other
+if (typeof afterEach === 'function' && !process.env.RTL_SKIP_CLEANUP) {
+  afterEach(async () => {
+    await asyncAct(async () => {})
+    cleanup()
+  })
+}
+
 // just re-export everything from dom-testing-library
 export * from '@testing-library/dom'
 export {render, cleanup, fireEvent, act}

tests/setup-env.js

@@ -1,6 +1 @@
 import '@testing-library/jest-dom/extend-expect'
-
-afterEach(() => {
-  // have to do a dynamic import so we don't mess up jest mocking for old-act.js
-  require('../src').cleanup()
-})