I'm trying to cover the plugin controller with unit tests, but when I try to run phpunit this error shows up:
Warning: Cannot modify header information - headers already sent by (output started at /craft/app/vendor/phpunit/phpunit/src/Util/Printer.php:172 ) in /craft/craft/app/helpers/JsonHelper.php on line 25
The same error indicates also line 26 and 27 of JsonHelper.php
Did someone already had this issue? Can somebody help me on this?
Thank you very much.