Angular 11 Unit Test Code Coverage is Now Breaking - unit-testing

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.
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?
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.

Answer 2

Also, I found that the reporters must have a subdir field:
Doesn't work
reporters: [
{ type: 'html' }
}
Doesn't work
reporters: [
{ type: 'html', subdir: '' }
}
Works:
reporters: [
{ type: 'html', subdir: 'report-html' }
}