The xmltv distribution contains a number of tools that can help you validate that a grabber behaves the way it is expected to.
tv_validate_grabber tests one grabber to see that it supports the correct command-line parameters and that it produces the correct output. See perldoc tv_validate_grabber for instructions.
The test_grabbers script is used to test all grabbers in the distribution at once. It can be found under grab/ in the source distribution of xmltv. To run it, cd to an empty directory and run it from there. It will automatically test all grabbers found in subdirectories relative to itself. It uses test.conf-files found in the subdirectory for each grabber. These can be created with
% ./grab/test_grabbers --configure --only xx
The test_grabbers script is run every night and published on the web. See XmltvStatus.