fix: code coverage incomplete on redirect (#660)

Co-authored-by: Matt Schile <mschile@gmail.com>
Co-authored-by: Cacie Prins <cacieprins@users.noreply.github.com>
Co-authored-by: Matthew Schile <mschile@cypress.io>

Author: 3 people

.circleci/config.yml

@@ -11,7 +11,7 @@ jobs:
     docker:
       - image: cimg/node:20.8.0
         environment:
-          # we don't need Cypress to check code styl
+          # we don't need Cypress to check code style
           CYPRESS_INSTALL_BINARY: '0'
     steps:
       - attach_workspace:
@@ -158,6 +158,7 @@ workflows:
                 - ts-example
                 - unit-tests-js
                 - use-webpack
+                - redirect
       - windows_test
       - publish:
           filters:
@@ -184,4 +185,5 @@ workflows:
             - test-ts-example
             - test-unit-tests-js
             - test-use-webpack
+            - test-redirect
             - windows_test

.nycrc.json

@@ -1,6 +1,6 @@
 {
   "exclude": [
-    "support-utils.js",
+    "support.js",
     "task-utils.js"
   ]
 }

support.js

@@ -72,13 +72,15 @@ const registerHooks = () => {
         return
       }
 
-      if (
-        Cypress._.find(windowCoverageObjects, {
-          coverage: applicationSourceCoverage
-        })
-      ) {
+      const existingCoverage = Cypress._.find(windowCoverageObjects, {
+        coverage: applicationSourceCoverage
+      })
+      if (existingCoverage) {
         // this application code coverage object is already known
-        // which can happen when combining `window:load` and `before` callbacks
+        // which can happen when combining `window:load` and `before` callbacks,
+        // it can also happen when the user navigates away and then returns to the page
+        // in which case we need to use new applicationSourceCoverage, because the old will not be updated anymore.
+        existingCoverage.coverage = applicationSourceCoverage
         return
       }
 

test-apps/redirect/.babelrc

@@ -0,0 +1,3 @@
+{
+  "plugins": ["istanbul"]
+}

test-apps/redirect/.nycrc.json

@@ -0,0 +1,5 @@
+{
+  "exclude": [
+    "app.js"
+  ]
+}

test-apps/redirect/README.md

@@ -0,0 +1,3 @@
+# example: redirect
+
+Tests a frontend app that redirects, through un-instrumented code, back to itself.

test-apps/redirect/app.js

@@ -0,0 +1,28 @@
+// This redirect code needs to be un-instrumented (excluded in .nycrc.json)
+// - If the redirect code is instrumented, Cypress would then treat them as different coverage objects and merge the code coverage (not testing what we want).
+// - If the redirect code is un-instrumented, Cypress can't tell them apart and will update the existing coverage object to point to the correct one (testing what we want).
+
+import { returnToApp } from './utils'
+
+// Timeouts are necessary to allow cypress to pick up the "initial" coverage object and compare it to the existing coverage objects.
+new Promise((resolve) => {
+  if (window.location.port === '1234' && !localStorage.getItem('visited')) {
+    localStorage.setItem('visited', true)
+    console.log('Not visited. Redirecting')
+    setTimeout(() => {
+      window.location.href = 'http://localhost:1235'
+    }, 500)
+  } else if (window.location.port === '1235') {
+    console.log('Redirecting back.')
+    setTimeout(() => {
+      window.location.href = 'http://localhost:1234'
+    }, 500)
+  } else {
+    console.log('Visited');
+    setTimeout(() => {
+      resolve()
+    }, 500)
+  }
+}).then(() => {
+  returnToApp()
+})

test-apps/redirect/cypress.config.js

@@ -0,0 +1,18 @@
+const { defineConfig } = require('cypress')
+
+module.exports = defineConfig({
+  fixturesFolder: false,
+  e2e: {
+    setupNodeEvents(on, config) {
+      require('@cypress/code-coverage/task')(on, config)
+      return config
+    },
+    baseUrl: 'http://localhost:1234',
+    env: {
+      codeCoverage: {
+        exclude: ['cypress/**/*.*']
+      }
+    },
+    chromeWebSecurity: false
+  }
+})

test-apps/redirect/cypress/e2e/spec.cy.js

@@ -0,0 +1,11 @@
+// enables intelligent code completion for Cypress commands
+// https://on.cypress.io/intelligent-code-completion
+/// <reference types="Cypress" />
+
+context('Page test', () => {
+  it('redirects back to the app', function() {
+    cy.clearLocalStorage()
+    cy.visit("http://localhost:1234")
+    cy.contains("Returned to app")
+  })
+})

test-apps/redirect/cypress/support/e2e.js

@@ -0,0 +1 @@
+import '@cypress/code-coverage/support'

test-apps/redirect/index.html

@@ -0,0 +1,4 @@
+<body>
+  <h2>Test page</h2>
+  <script src="app.js"></script>
+</body>

test-apps/redirect/package.json

@@ -0,0 +1,16 @@
+{
+  "name": "example-redirect",
+  "description": "Tests a frontend app that redirects, through un-instrumented code, back to itself.",
+  "devDependencies": {
+    "@babel/core": "^7.12.0"
+  },
+  "scripts": {
+    "cy:run": "cypress run",
+    "start:app": "parcel serve -p 1234 index.html",
+    "start:other-app": "parcel serve -p 1235 index.html",
+    "pretest": "rimraf .nyc_output .cache coverage dist",
+    "test": "start-test start:app http://localhost:1234 start:other-app http://localhost:1235 cy:run",
+    "coverage:verify": "npx nyc report --check-coverage true --lines 100",
+    "coverage:check-files": "check-coverage utils.js && only-covered utils.js"
+  }
+}

test-apps/redirect/utils.js

@@ -0,0 +1,4 @@
+export const returnToApp = () => {
+  document.body
+    .appendChild(document.createTextNode('Returned to app'))
+}