Can't run unit tests on iOS device

I can't run unit tests on my iPhone. I need to run the unit tests on the phone because I need to access devices on the phone that the simulator cannot emulate. But every time I am get a breakpoint:

Thread 1: EXC_BREAKPOINT (code=1, subcode=0x1200c1088)

The code highlighted at the breakpoint is:

dyld`dyld_fatal_error:
->  0x1200c1088 <+0>: brk    #0x3

Has anyone seen this before?