Apple has begun widespread testing of the latest update to Mac OS X 10.5. The update represents the third update to OS X Leopard and although in the early stages already contains over 75 changes.

Apple has asked developers to focus testing in Mac OS X 10.5.3 to the following areas; AddressBook, AppleScript, Audio, Back To My Mac, Dashboard, the Dock, DVD Player, Finder, Graphics, iCal, Mail, Portable Home Directories, Printing, Rosetta, Spaces, Spotlight, Time Machine, and VoiceOver.

Apple has also turned its efforts to bug fixing in iCal, Core Animation, Installer app, Spotlight, Preview, Mail alarms, Spaces, Stacks and the Dock.

Mac OS X 10.5.3 is expected to be released in late April.