Explain about the activation coverage that is required to run the unit test

Author: datamweb

tests/README.md

@@ -19,7 +19,7 @@ If running under OS X or Linux, you can create a symbolic link to make running t
 	> ln -s ./vendor/bin/phpunit ./phpunit
 
 You also need to install [XDebug](https://xdebug.org/docs/install) in order
-for code coverage to be calculated successfully.
+for code coverage to be calculated successfully. After installing `XDebug`, you must add `xdebug.mode=coverage` in the **php.ini** file to enable code coverage.
 
 ## Setting Up