I just started with PHPUnit. Some simple tests I wrote are working. So in general PHPUnit is up and running. There\'s something wrong with the MySQLi class though.
I
PHPUnit normally runs within the CLI - command line interface.
The PHP you've got there is different than with the webserver. Different binary and often a different configuration as well.
$ php -r "new mysqli();"
Should give you the same error. Verify where the binary and configuration is located:
$ which php
And
$ php -i | grep ini
Ensure you've got the extension for the mysqli class installed and enabled. Once configured you should be able to run your unit-tests flawlessly.