To add a bit to what lomapaseo wrote:
Blade out events are extremely dynamic - every one is different and the results are not really repeatable. They run the full blown engine test once (generally after several smaller 'rig tests' to make sure things will work as designed) and hope that it passes - pass/fail being nothing goes out tangentially through the containment system, nothing important 'falls off', and the engine quits 'gracefully'. The blade is released by a small explosive charge in the root with the engine running at redline N1. The blade will hit the next (trailing) blade and containment ring (even the older steel ones would distort very dramatically), then the pieces tend to come back in and cause havoc, damaging the rest of the fan blades (occasionally even breaking off another blade), while the sudden imbalance causes massive vibrations of the whole mess. If you get a chance to watch one of the slow motion videos, do it - the amount of destruction and way everything moves around and distorts is simply amazing. By design, the fan disc shouldn't fail, although it'll likely lose bits of the fan blade attachment dovetails. Way back ~30 years ago when they did the fan blade out for the original PW4000, part of a fan blade made it through the (steel) containment ring and was embedded in the (fan case mounted) FADEC - interestingly that was considered a 'pass' since it didn't escape the engine...
Cause of a fan blade out are varied - oftentimes it's not an entire blade - the blade fails someplace outboard of the root (metal fatigue - possibly caused by FOD induced blade damage), I recall a Trent 800 event which was caused by wear of the blade dovetail due to inadequate lubrication of the dovetail. They do the test releasing an entire blade since that's considered to be worst case.
On the original GE90, when they did the blade out test the containment system worked, and the engine shutdown gracefully, but all sorts of stuff fell off - the inlet, parts of the gearbox, etc. GE argued that they could show by analysis that they'd solved the problem of stuff falling off, but the FAA didn't buy it and made them re-run the test, destroying another expensive engine in the process.