Is it possible to run Karma with no browsers at all?

I am going to add my two cents to this.

Correct - Karma requires a browser to run. BUT - you can run Chrome in Headless mode, which means although you do need the browser installed, it will not open it's UI, and you can therefore run the tests purely through an SSH session for example.

We used this configuration for our CI/CD deployments. Our Docker image for running the tests had Chrome installed and we ran them with Chrome headless mode. Worked like a charm.

To use this, simply modify your browsers property in your karma.conf.js

browsers: ['ChromeHeadless']

Hope this might help someone out there who may be looking for something similar...

Karma needs a browser to be set.

You can make use of PhantomJS instead of Chrome.
Indeed, it's more discreet than a traditional browser launch.

This question and answer is very relevant as of today (soon 2018, > angular2, @angular/cli, typescript, ...).

Here is a small update, based on what i found as useful on the net:

Say you have an angular cli generated project that has not been tempered with. Say you want to use PhantomJS to run your angular2 tests (nothing shocking).

Start by installing PhantomJS launcher for Karma in your project

npm i --save-dev karma-phantomjs-launcher

Next you have to update the karma.conf.js file as follows:

First the the plugins properties:

plugins: [  require('karma-jasmine'),  require('karma-phantomjs-launcher'),  require('karma-jasmine-html-reporter'),  require('karma-coverage-istanbul-reporter'),  require('@angular/cli/plugins/karma')],

Then the browser properties

browsers: [ 'PhantomJS' ],

Running the test at this point, you will probably stumble on the following error:

PhantomJS 2.1.1 (Windows 7 0.0.0) ERROR  TypeError: pre,template,textarea,script,style is not iterable!  at http://localhost:9876/_karma_webpack_/polyfills.bundle.js:792

Basically, that means your PhantomJS needs different polyfills. Uncomment the following lines in your src\polyfills.ts

import 'core-js/es6/symbol';import 'core-js/es6/object';import 'core-js/es6/function';import 'core-js/es6/parse-int';import 'core-js/es6/parse-float';import 'core-js/es6/number';import 'core-js/es6/math';import 'core-js/es6/string';import 'core-js/es6/date';import 'core-js/es6/array';import 'core-js/es6/regexp';import 'core-js/es6/map';import 'core-js/es6/weak-map';import 'core-js/es6/set';

Last but not least, here are the links that helped me work this out:

How to run jasmine tests without browser ?

New angular-cli app not working on iphone 4s