"Can not load "coverage", it is not registered!" error when running

[apond]

I install karma-coverage like this:
npm install karma-coverage --save-dev

I have a package file that contains this:
"devDependencies": {
"karma": "0.10.2",
"karma-coverage": "0.1.5",
"karma-junit-reporter": "0.1.0",
"karma-jasmine": "0.1.3",
"karma-chrome-launcher": "0.1.0",
"karma-ie-launcher": "0.1.1",
"karma-safari-launcher": "0.1.1",
"karma-firefox-launcher": "0.1.0"
},

And a config file that looks contains this:
// test results reporter to use
// possible values: 'dots', 'progress', 'junit', 'growl', 'coverage'
reporters: ['dots', 'junit', 'coverage'],

preprocessors: {
  // source files, that you wanna generate coverage for
  // do not include tests or libraries
  // (these files will be instrumented by Istanbul)
  'jstarget/**/*.js': ['coverage']
},

// configure the coverage reporter
coverageReporter: {
  type : 'html',
  dir : 'coverage/'
},

And I get an error that looks like this:
WARN [reporter]: Can not load "coverage", it is not registered!
Perhaps you are missing some plugin?

What do I need to do?

[apond]

I forgot to add karma-coverage to the list of plugins. This should be added to the sample config in the readme.

[vojtajina]

@apond what is your set up look like?

The recommended way is to install karma and all the plugins in your project (not global). Then, Karma automatically loads all the plugins (karma-*).

[apond]

@vojtajina All of my setup is shown above. I have installed karma and the plugins. Without the plugins listed in the config file this doesn't work. What is the alternative?

[vojtajina]

You can list the plugins, but it should work without it. By default, Karma loads karma-* modules that are siblings to karma module.

[ryoia]

I am having the same problem currently, it worked fine yesterday, but now it says can not load 'webpack'/'coverage'/'sourcemap' did you forget to install it? i have them in the devDep., and did npm i already. Also having 'Perhaps you are missing some plugin' for those 3 as well.

[davidpricedev]

I had this problem as well. I was able to get things working once I deleted all the global karma packages and reinstalled karma-cli as the only global (karma-related) package.

[ryoia]

I got it working by doing the same thing, thanks for replying!

[simon-nguyen]

@davidpricedev @ryoia I just got the same issue working with webpack, and when I run karma start, it said "cannot load webpack, source-map" I did as you suggested and now it works perfectly. Thanks.

[ryoia]

awesome @simon-nguyen !

[eelogic]

I ran karma with gulp and got the same issue, fixed as @apond mentioned:
plugins: [
'karma-webpack', 'karma-coverage'
]

[ekkis]

I've found that if I declare the plugins option with any values, it fails to load all the karma-* modules. if I remove it altogether then it works fine. I'm not sure why I would ever want to use plugins in that case, since I could only be declaring plugins that would be loaded anyway, without the declaration

[sukrosono]

I still facing that error with out explicitly specify karma-coverage as plugins.
as far as i remember i install karma-cli and karma-coverage globally.
IMO , should update the README.md