karma test runner not running any tests

Under karma.config.js, set either singleRun or autoWatch to true. In your case both of them are set to false, hence karma is not running the tests.

singleRun: If true, it captures browsers, runs tests and exits with 0 exit code (if all tests passed) or 1 exit code (if any test failed).

singleRun: true

autoWatch: Enable or disable watching files and executing the tests whenever one of these files changes. Incase you want to watch your files.

autoWatch: true

Simple but sometimes overlooked cause: ensure you don't have syntax or compilation errors.

If running a Karma test for JavaScript via your IDE, you may have a syntax error which doesn't appear when you run your tests. This leads to Karma issuing the message "no tests were found".

I ran it under WebStorm; the error appeared under the "Karma Server" tab, while the "No tests were found" message appeared under "Test Run" (both tabs under "Run" or "Debug" tool window).