@commuting pilot: there is one medical for the assessment. We call it the BIG medical and you have will the following done: (I might miss one or two)
1. Ears, Nose, Throat - the easy part
2. Eyes exam - no real issues here. Fairly standard. If you have glasses, bring your prescription.
3. Weight and flexibility - another easy part
4. Chest X-ray - no real issues here normally.
4. EEG: Some brainwave thing. You wear a bonnet with a bunch of electrodes attached. They are looking for epilepsy.
5. Stress ECG.
6. Normal ECG? (if I recall)
7. MRI
8. Blood and urine check
9. Blood pressure check
10. Liver and kidney ultrasound.
If you pass the medical and are offered a job, then there is another medical you will have to do for your resident visa. Regrettably, this will include another chest x-ray. Generally, this is much more forgiving and straight forward.
If you have had any minor surgery from a long-time ago, just put NO in the box that asks. If of course you've had surgery which is impossible to disguise, then don't. Bring along as much documentation that you can.
Tip: 3 weeks prior to your medical exam, stop drinking, liver detox (I recommend Milk Thistle for the 3 week period prior), avoid as much red meat as possible and DO NOT take any Tylenol at least a week prior to the medical - it spikes your ALT (a liver enzyme)! Milk Thistle is highly effective in lowering the ALT/GPT numbers for your liver check.
I hope this helps and good luck.