Fixing cypress-io#91

* Adding tests for React.memo
* Adding tests for React.forwardRef
* Adding basic hook tests

cypress/integration/counter-with-hooks.spec.js

@@ -0,0 +1,13 @@
+/// <reference types="cypress" />
+/// <reference types="../../lib" />
+
+import React from 'react'
+import CounterWithHooks from '../../src/counter-with-hooks.jsx'
+
+/* eslint-env mocha */
+describe('CounterWithHooks component', function () {
+  it('works', function () {
+    cy.mount(<CounterWithHooks initialCount={3} />)
+    cy.contains('3')
+  })
+})

cypress/integration/forward-ref.spec.js

@@ -0,0 +1,21 @@
+/// <reference types="cypress" />
+/// <reference types="../../lib" />
+
+import React from 'react'
+import Button from '../../src/forward-ref.jsx'
+
+/* eslint-env mocha */
+describe('Button component', function () {
+  it('works', function () {
+    cy.mount(<Button>Hello, World</Button>)
+    cy.contains('Hello, World')
+  })
+
+  it('forwards refs as expected', function () {
+    const ref = React.createRef();
+
+    cy.mount(<Button className="testing" ref={ref}>Hello, World</Button>);
+    expect(ref).to.have.property('current');
+    // expect(ref.current).not.be.null;
+  })
+})

cypress/integration/pure-component.spec.js

@@ -0,0 +1,13 @@
+/// <reference types="cypress" />
+/// <reference types="../../lib" />
+
+import React from 'react'
+import Button from '../../src/pure-component.jsx'
+
+/* eslint-env mocha */
+describe('Button pure component', function () {
+  it('works', function () {
+    cy.mount(<Button>Hello</Button>)
+    cy.contains('Hello')
+  })
+})

lib/index.d.ts

@@ -9,6 +9,16 @@ interface ReactModule {
   source: string
 }
 
+/**
+ * The `type` property from the transpiled JSX object.
+ * @example
+ * const { type } = React.createElement('div', null, 'Hello')
+ * const { type } = <div>Hello</div>
+ */
+interface JSX extends Function {
+  displayName: string
+}
+
 declare namespace Cypress {
   interface Cypress {
     stylesCache: any

lib/index.ts

@@ -18,6 +18,57 @@ const setAlert = w => {
   return w
 }
 
+const cachedDisplayNames: WeakMap<JSX, string> = new WeakMap();
+
+/**
+ * Gets the display name of the component when possible.
+ * @param type {JSX} The type object returned from creating the react element.
+ * @param fallbackName {string} The alias, or fallback name to use when the name cannot be derived.
+ * @link https://github.com/facebook/react-devtools/blob/master/backend/getDisplayName.js
+ */
+function getDisplayName(type: JSX, fallbackName: string = 'Unknown'): string {
+  const nameFromCache = cachedDisplayNames.get(type)
+
+  if (nameFromCache != null) {
+    return nameFromCache
+  }
+
+  let displayName: string
+
+  // The displayName property is not guaranteed to be a string.
+  // It's only safe to use for our purposes if it's a string.
+  // github.com/facebook/react-devtools/issues/803
+  if (typeof type.displayName === 'string') {
+    displayName = type.displayName
+  }
+
+  if (!displayName) {
+    displayName = type.name || fallbackName
+  }
+
+  // Facebook-specific hack to turn "Image [from Image.react]" into just "Image".
+  // We need displayName with module name for error reports but it clutters the DevTools.
+  const match = displayName.match(/^(.*) \[from (.*)\]$/)
+
+  if (match) {
+    const componentName = match[1]
+    const moduleName = match[2]
+
+    if (componentName && moduleName) {
+      if (
+        moduleName === componentName ||
+        moduleName.startsWith(componentName + '.')
+      ) {
+        displayName = componentName
+      }
+    }
+  }
+
+  cachedDisplayNames.set(type, displayName)
+
+  return displayName
+}
+
 /** Initialize an empty document w/ ReactDOM and DOM events.
     @function   cy.injectReactDOM
 **/
@@ -106,7 +157,7 @@ Cypress.Commands.add('copyComponentStyles', component => {
  **/
 export const mount = (jsx, alias) => {
   // Get the display name property via the component constructor
-  const displayname = alias || jsx.type.prototype.constructor.name
+  const displayname = getDisplayName(jsx.type, alias)
 
   let cmd
 
@@ -165,7 +216,8 @@ Cypress.Commands.overwrite('get', (originalFn, selector, options) => {
       }
     case 'function':
       // If attempting to use the component name without JSX (testing in .js/.ts files)
-      const displayname = selector.prototype.constructor.name
+      // const displayname = selector.prototype.constructor.name
+      const displayname = getDisplayName(selector.type);
       return originalFn(`@${displayname}`, options)
     default:
       return originalFn(selector, options)

src/counter-with-hooks.jsx

@@ -0,0 +1,18 @@
+import React from 'react';
+
+export default function CounterWithHooks({ initialCount = 0 }) {
+    const [count, setCount] = React.useState(initialCount);
+
+    const handleCountIncrement = React.useCallback(() => {
+        setCount(count + 1);
+    }, [count]);
+
+    return (
+        <>
+            <div className="counter">
+                {count}
+            </div>
+            <button onClick={handleCountIncrement}>+</button>
+        </>
+    )
+}

src/forward-ref.jsx

@@ -0,0 +1,5 @@
+import React from 'react';
+
+const Button = React.forwardRef(({ children, ...rest }, ref) => <button {...rest} ref={ref}>{children}</button>);
+
+export default Button;

src/pure-component.jsx

@@ -0,0 +1,7 @@
+import React from 'react';
+
+const Button = ({ children, ...rest }) => {
+    return <button {...rest}>{children}</button>;
+};
+
+export default React.memo(Button);