Original answer of December 29, 2010:
Ignore Apple's distinction between “logic tests” and “application tests.” Use GTM instead. You will have one test goal that works either on the simulator or on the device, and can be debugged without additional configuration.
New answer:
Xcode inline unit testing has come a long way since. I switched from GTM to OCUnit. See http://qualitycoding.org/xcode-unit-testing/
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