The hardware under test either can be the on-chip peripherals of a microcontroller or hardware external to the microcontroller. This enables a so-called hardware-in-the-loop (HIL) test for unit and integration testing. Such a test makes especially sense if the microcontroller is implemented as soft core in a FPGA, because in this case the on-chip peripherals actually are not hardware, but software, which might change during the course of the development and therefore needs repetitive testing.
To accomplish such tests, special test hardware and software is used, adapted to the hardware under test in question.
Tessy usually uses a debugger as test execution environment. Such a debugger needs to provide a special feature in order to enable Tessy to incorporate hardware in module / unit / integration testing. Unfortunately, not all debuggers dispose of this feature. Hence, it is not possible to incorporate hardware in module / unit / integration testing with every debugger.