Angular 11 Unit Test Code Coverage is Now Breaking

Question

Prior to upgrading to Angular 11, I ran my unit tests with code coverage via the following command:

ng test --project my-app --code-coverage true

When I upgraded my project to Angular 11, I was still able to do my code coverage tests, but I started getting a message saying "'karma-coverage-istanbul-reporter' usage has been deprecated since version 11". It asked me to install karma-coverage and update karma.conf.js. So I did what it asked. I installed karma-coverage and karma via this command:

npm install karma karma-coverage --save-dev

As a result, I see in my package.json, under devDependencies, the entries for karma:

"karma": "^5.2.3",<br>
"karma-coverage": "^2.0.3"

I updated my karma.conf.js file. The following is what exists, everything was as it was originally except for my comments:

module.exports = function (config) {
  config.set({
    basePath: '',
    frameworks: ['jasmine', '@angular-devkit/build-angular'],
    plugins: [
      require('karma-jasmine'),
      require('karma-chrome-launcher'),
      require('karma-jasmine-html-reporter'),
      require('karma-coverage'), // NEWLY ADDED
      // ORIGINALLY HERE NOW REMOVED require('karma-coverage-istanbul-reporter'),
      require('@angular-devkit/build-angular/plugins/karma')
    ],
    client: {
      clearContext: false // leave Jasmine Spec Runner output visible in browser
    },
    reporters: ['progress', 'kjhtml', 'coverage'],
    // coverageIstanbulReporter NO LONGER HERE
    //coverageIstanbulReporter: {
    //  dir: require('path').join(__dirname, '../../coverage/my-app'),
    //  reports: ['html', 'lcovonly', 'text-summary'],
    //  fixWebpackSourcePaths: true
    //},
    // coverReporter NEWLY ADDED
    coverageReporter: {
      dir: 'build/reports/coverage',
      reporters: [
        { type: 'html', subdir: 'report-html' },
        { type: 'lcov', subdir: 'report-lcov' }
      ]
    },
    // THE FOLLOWING REMAINED AS IS
    port: 9876,
    colors: true,
    logLevel: config.LOG_INFO,
    autoWatch: true,
    browsers: ['Chrome'],
    singleRun: false,
    restartOnFileChange: true
  });
};

Having made this update, two things are happening and I can't figure out why.

1. When I run my normal code coverage command, I get the following error: "Server start failed on port 9876: Error: karma-coverage must be installed in order to run code coverage." I did install it, as my package.json indicates, but for some reason my project doesn't recognize this. In addition, if I add back the karma-coverage-istanbul-reporter require method to my conf.js file, coverage works fine, but I still get that deprecation message. Can anyone explain to me why I may be getting this error?

2. When I run my tests without coverage, I now get multiple warnings that I never got before, like: "Unable to determine file type from the file extension, defaulting to js. To silence the warning specify a valid type for C:/Angular/my-project/projects/my-app/src/app/app.component.spec.ts in the configuration file." What would I need to do to resolve this?

EDIT: I found the answer. Inside the coverageReporter object, you need to add the fixWebpackSourcePaths property to true:

coverageReporter: {
  dir: 'build/reports/coverage',
  reporters: [
    { type: 'html', subdir: 'report-html' },
    { type: 'lcov', subdir: 'report-lcov' }
  ],
  fixWebpackSourcePaths: true
},

Answer 1

The trick for me was to remove 'coverage' from the reporters. It should just be:

reporters: ['progress', 'kjhtml'],

The coverage report is then created as expected without weird warnings being thrown.

This seems to be the Angular way, have a look at the karma.conf.js generated by the ng new schematics.