feat: add code coverage merge command

.circleci/config.yml

@@ -2,7 +2,7 @@
 version: 2.1
 orbs:
   # https://github.com/cypress-io/circleci-orb
-  cypress: cypress-io/cypress@2 # used to run e2e tests
+  cypress: cypress-io/cypress@2.2.0 # used to run e2e tests
   node: circleci/node@1.1.6 # used to publish new NPM version
   win: circleci/windows@2 # run a test job on Windows
 
@@ -126,6 +126,36 @@ workflows:
                 command: npm run check
                 working_directory: examples/backend
 
+      - cypress/run:
+          name: merge coverage
+          executor: cypress/browsers-chrome99-ff97
+          requires:
+            - cypress/install
+          # grab the workspace created by cypress/install job
+          attach-workspace: true
+          working_directory: examples/merge-coverage
+          command: 'npm run cy:run1 && npm run report && npm run cy:run2 && npm run report'
+
+          # there are no jobs to follow this one
+          # so no need to save the workspace files (saves time)
+          no-workspace: true
+          post-steps:
+            - run:
+                command: npm run merge
+                working_directory: examples/merge-coverage
+            # store the created coverage report folder
+            # you can click on it in the CircleCI UI
+            # to see live static HTML site
+            - store_artifacts:
+                path: examples/merge-coverage/coverage
+            - run:
+                command: npm run report
+                working_directory: examples/merge-coverage
+            - run:
+                name: Check code coverage 📈
+                command: npm run check
+                working_directory: examples/merge-coverage
+
       - cypress/run:
           name: fullstack coverage
           requires:

.gitignore

@@ -10,3 +10,5 @@ cypress-coverage/
 examples/*/cypress/videos
 examples/*/cypress/screenshots
 yarn.lock
+cc1
+cc2

README.md

@@ -501,6 +501,31 @@ npm run dev
 npm run dev:no:coverage
 ```
 
+## Merge coverage reports
+
+When running tests in parallel, you can download all coverage folders into one top folder and then merge the coverage and regenerate new combined report using `cc-merge` command included in this module.
+
+For example, if this is the top folder with downloaded coverage subfolders:
+
+```
+project/
+  reports/
+    one/
+      coverage-final.json
+    two/
+      coverage-final.json
+    three/
+      coverage-final.json
+```
+
+Use this command to combine all `coverage-final.json` files
+
+```
+npx cc-merge reports
+```
+
+The coverage will be written into `.nyc_output` folder (which is automatically cleared) and the reports will be written into `coverage` folder.
+
 ## Links
 
 - 🎓 Take my course [Testing The Swag Store](https://cypress.tips/courses/swag-store) that shows e2e and component code coverage

bin/cc-merge.js

@@ -0,0 +1,63 @@
+#!/usr/bin/env node
+
+const debug = require('debug')('code-coverage')
+
+// finds all "coverage-final.json" files in the give folder
+// and merges them into a single "cc-merged/out.json" file
+// Use:
+// npx cc-merge <top coverage folder>
+const topCoverageFolder = process.argv[2]
+if (!topCoverageFolder) {
+  console.error('use: npx cc-merge <top coverage folder>')
+  process.exit(1)
+}
+
+const coverageFilename = 'coverage-final.json'
+debug('looking for %s files in %s', coverageFilename, topCoverageFolder)
+
+const fs = require('fs')
+const rimraf = require('rimraf')
+const path = require('path')
+const globby = require('globby')
+const allFiles = globby.sync(`**/${coverageFilename}`, {
+  absolute: true,
+  cwd: topCoverageFolder,
+})
+debug('found %d coverage files', allFiles.length)
+debug(allFiles.join(','))
+
+if (!allFiles.length) {
+  console.error(
+    'Could not find any %s files in the folder %s',
+    coverageFilename,
+    topCoverageFolder,
+  )
+  process.exit(1)
+}
+
+const nycOutputFolder = '.nyc_output'
+if (fs.existsSync(nycOutputFolder)) {
+  debug('deleting the existing folder %s', nycOutputFolder)
+  rimraf.nativeSync(nycOutputFolder)
+}
+
+if (!fs.existsSync(nycOutputFolder)) {
+  debug('creating folder %s', nycOutputFolder)
+  fs.mkdirSync(nycOutputFolder)
+}
+allFiles.forEach((filename, k) => {
+  const outputFilename = path.join(nycOutputFolder, `c-${k + 1}.json`)
+  fs.copyFileSync(filename, outputFilename)
+  debug('%d: copied %s to %s', k + 1, filename, outputFilename)
+})
+
+const { getNycOptions } = require('../task-utils')
+
+const processWorkingDirectory = process.cwd()
+const nycReportOptions = getNycOptions(processWorkingDirectory)
+debug('calling NYC reporter with options %o', nycReportOptions)
+debug('current working directory is %s', processWorkingDirectory)
+const NYC = require('nyc')
+const nyc = new NYC(nycReportOptions)
+
+nyc.report()

examples/merge-coverage/.babelrc

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

examples/merge-coverage/README.md

@@ -0,0 +1,3 @@
+# example: merge-coverage
+
+Run each spec one by one, producing partial report. Then use cc-merge to merge them into a single combined report, and then produce the final report.

examples/merge-coverage/cypress.config.js

@@ -0,0 +1,18 @@
+const { defineConfig } = require('cypress')
+
+module.exports = defineConfig({
+  e2e: {
+    env: {
+      coverage: {
+        exclude: '**/cypress/**',
+      },
+    },
+    fixturesFolder: false,
+    video: false,
+    // We've imported your old cypress plugins here.
+    // You may want to clean this up later by importing these.
+    setupNodeEvents(on, config) {
+      return require('./cypress/plugins/index.js')(on, config)
+    },
+  },
+})

examples/merge-coverage/cypress/e2e/add.cy.js

@@ -0,0 +1,6 @@
+/// <reference types="cypress" />
+import { add } from '../../src/math'
+
+it('adds two numbers', () => {
+  expect(add(2, 3)).to.equal(5)
+})

examples/merge-coverage/cypress/e2e/sub.cy.js

@@ -0,0 +1,6 @@
+/// <reference types="cypress" />
+import { sub } from '../../src/math'
+
+it('subtracts two numbers', () => {
+  expect(sub(2, 3)).to.equal(-1)
+})

examples/merge-coverage/cypress/plugins/index.js

@@ -0,0 +1,5 @@
+module.exports = (on, config) => {
+  require('../../../../task')(on, config)
+  on('file:preprocessor', require('../../../../use-babelrc'))
+  return config
+}

examples/merge-coverage/cypress/support/e2e.js

@@ -0,0 +1 @@
+import '../../../../support'

examples/merge-coverage/package.json

@@ -0,0 +1,15 @@
+{
+  "name": "example-merge-coverage",
+  "description": "Merge partial code coverage reports",
+  "scripts": {
+    "cy:open": "../../node_modules/.bin/cypress open",
+    "cy:run1": "npm run clean && rm -rf cc1 && ../../node_modules/.bin/cypress run --spec cypress/e2e/add.cy.js && mv coverage cc1",
+    "cy:run2": "npm run clean && rm -rf cc2 && ../../node_modules/.bin/cypress run --spec cypress/e2e/sub.cy.js && mv coverage cc2",
+    "check:covered": "../../node_modules/.bin/check-coverage --from coverage/coverage-final.json math.js",
+    "check:extras": "../../node_modules/.bin/only-covered --from coverage/coverage-final.json math.js",
+    "check": "npm run check:covered && npm run check:extras",
+    "clean": "rm -rf .nyc_output && rm -rf coverage",
+    "merge": "DEBUG=code-coverage ../../bin/cc-merge.js .",
+    "report": "../../node_modules/.bin/nyc report"
+  }
+}

examples/merge-coverage/src/math.js

@@ -0,0 +1,19 @@
+/**
+ * Adds two numbers together
+ * @param {number} a
+ * @param {number} b
+ */
+export const add = (a, b) => {
+  console.log('add %d to %d', a, b)
+  return a + b
+}
+
+/**
+ * subtracts numbers
+ * @param {number} a
+ * @param {number} b
+ */
+export const sub = (a, b) => {
+  console.log('sub %d to %d', a, b)
+  return a - b
+}