Optional field, if you do not enter all test will run. If entered specify the test categories to run. You can use logical operators like:

Cateogry Filter	Result
Priority1	Any test with category Priority1
Priority1&SpeedTest	Test that have both Priority1 and SpeedTest categories
Priority1|SpeedTest	Tests that have either Priority1 or SpeedTest categories
Priority1&!SpeedTest	Test that have Priority1 category and also do not have SpeedTest category.

Command Line Argument: /category