Cannot get code coverage with Cypress + Istanbul

问题

I tried setting up code coverage in an Angular 8 project using Cypress and istanbul nyc.

I managed to get the code instrumented (the global variable __coverage__ is properly set) :

and the coverage file generated in .nyc_output after running cypress:open

But the generated coverage report is empty:

$ cat coverage/coverage-final.json
{}

Same result when I execute the command:

$ npx nyc report --report-dir ./coverage --temp-dir .nyc_output --reporter=text
----------|----------|----------|----------|----------|-------------------|
File      |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
----------|----------|----------|----------|----------|-------------------|
All files |        0 |        0 |        0 |        0 |                   |
----------|----------|----------|----------|----------|-------------------|

Here is my package.json devDependencies:

"devDependencies": {
  "@angular-devkit/build-angular": "^0.803.3",
  "@angular-devkit/build-optimizer": "^0.803.3",
  "@angular/cli": "^8.3.3",
  "@angular/compiler-cli": "8.2.5",
  "@angular/language-service": "8.2.5",
  "@briebug/cypress-schematic": "^2.0.0",
  "@cypress/code-coverage": "^1.10.1",
  "@cypress/webpack-preprocessor": "^4.1.0",
  "@istanbuljs/nyc-config-typescript": "^0.1.3",
  "@types/jasmine": "^3.4.0",
  "@types/jasminewd2": "^2.0.6",
  "@types/node": "^12.7.4",
  "babel-plugin-istanbul": "^5.2.0",
  "codelyzer": "^5.1.0",
  "cypress": "^3.4.1",
  "istanbul-instrumenter-loader": "^3.0.1",
  "istanbul-lib-coverage": "^2.0.5",
  "jasmine-core": "^3.4.0",
  "jasmine-spec-reporter": "4.2.1",
  "karma": "^4.3.0",
  "karma-chrome-launcher": "^3.1.0",
  "karma-cli": "^2.0.0",
  "karma-coverage-istanbul-reporter": "^2.1.0",
  "karma-jasmine": "^2.0.1",
  "karma-jasmine-html-reporter": "^1.4.2",
  "mochawesome": "^4.1.0",
  "ngx-build-plus": "^8.1.4",
  "nyc": "^14.1.1",
  "protractor": "^5.4.2",
  "protractor-html-reporter-2": "^1.0.4",
  "protractor-http-client": "^1.0.4",
  "source-map-support": "^0.5.13",
  "ts-node": "^8.3.0",
  "tslib": "^1.10.0",
  "tslint": "^5.19.0",
  "typescript": "3.5.3"
}

And my .nycrc.json:

{
    "cache": false,
    "extension": [
      ".ts",
      ".tsx"
    ],
    "exclude": [
      "**/*.d.ts",
      "coverage/**",
      "packages/*/test/**",
      "test/**",
      "test{,-*}.ts",
      "**/*{.,-}{test,spec}.ts",
      "**/__tests__/**",
      "**/node_modules/**"
    ],
    "all": true,
    "check-coverage": true,
    "require": [
      "ts-node/register"
    ],
    "temp-directory": ".nyc_output",
    "sourceMap": false,
    "instrument": false,
    "include": ["src/**/*.ts", "src/**/*.tsx"]
}

回答1:

It seems to be an issue in nyc when excludeAfterRemap is true.

setting it to false fixed the problem.

回答2:

Here is details description step by step. https://docs.cypress.io/guides/tooling/code-coverage.html#E2E-code-coverage

I think you are missing code-coverage/support file in index.js Please do follow change and run. I think you should be good.

    // cypress/support/index.js
       import '@cypress/code-coverage/support'

   // cypress/plugins/index.js   
      module.exports = (on, config) => {
      on('task', require('@cypress/code-coverage/task'))}

When you run the Cypress tests now, you should see a few commands after the tests finish. We have highlighted these commands using a green rectangle below.

回答3:

With @cypress/code-coverage, you have to know that the plugin does not instrument your code. You need to use the babel-plugin-istanbul plugin for code instruments.

if you are already using babel, you need to add the plugin to your .babelrc as follow:

{
  "plugins": ["istanbul"]
}

For more info check https://github.com/cypress-io/code-coverage#instrument-your-application

来源：https://stackoverflow.com/questions/57876922/cannot-get-code-coverage-with-cypress-istanbul