Following from a few posts above
The engine test is just that, nothing more. The idea is to demonstrate the engine capabilities and provide enough load data to the various installers to use in estimating the loads on their nacelle and their pylon mounts. This goes along way in later analysis to demonstrate to t the FAA that the engine has the capability to be safely installed on multiple aircraft designs. It's then up to the Boeings and Airbus to design their parts to remain safe,
The last thing the engine guy wants is to have some sort of test apparatus that screws up the engine to demonstrate itself and to generate useful load data. Hence interface parts like inlets and nacelles are chosen simply as end-loading attachments. The inlets must operate at zero static speed and max power so they really don't look like flight inlets and then ejected blade pieces just screw themselves forward and out the inlet rather than through the side (just like a turbine exhaust pipe)
The FAA is quite tolerant of the measured load capability in the presence of containment and rundown of the engine debris. Some of us like numbers more than just a one-off test..
On the engine side the worst loads to the mounts and fan bearing supports etc. occur in about 5 rev of the fan, after that it's just run-down loads and changing frequencies to the stuff hung off the engine. This quite often shows up in large oscillations as the plane slows down for landing. Typically nothing to worry about except for passenger comfort
Obviously there are some lessons to be learnt here that will have to wait for the investigation to complete