create test cases checking expected outcomes

[riebl]

At the moment, we have a number of smoke tests that just abort if something goes utterly wrong. However, smaller problems or changes in behaviour may be undetected.

I would like to have the following aspects under test (non-exclusive):

• a station's position is properly initialised and updated (see Receive messages - RSU #59)
• generated messages are actually transmitted by the radio
• CBR calculation produces reasonable results