part of test verifies that the pack on the cylinder in question hasn't gone bad - if swapping a pack causes the issue to follow where the pack is moved, its the pack. Otherwise its an issue with the circuit driving that coil pack for the cylinder in question.
To really test spark - coil pack is removed but still connected to the harness, spark plug inserted (and grounded) and then a visual inspection of spark (or not) is done while engine is cranking....