Is there a voltage drop test that ensure that electrical wiring in house is safe?
Your math all checks out.  You can calculate the actual resistance (sounds like in excess of 1.0 ohms) and/or you can go to a "voltage drop calculator" and compare the voltage drop you should get given your length, vs what you're actually getting.  

Certainly, 150 watts cannot be attributed to wire drop alone.  Heat is being made somewhere.  If you inspect the circuit after it's run at spec for awhile, you would find the problem area to be notably warm.   At 9A nothing should be warm.  Unless the wiring is much longer than you think, it is certainly a bad splice. Backstabs are the usual culprit, but so can be limp wristed wire nuts.  

The dead giveaway of bad wire-nut work is when the nuts are taped on; the person has found that they won't hold together by themselves, they think that is normal for wire nuts, and they think tape is the cure.  Actually, the refusing to hold together indicates they are also making poor electrical connection, and that means arcing faults will develop inside the nut.

You may want to consider fitting an arc-fault breaker on this circuit. That is your best bet to improving safety given these symptoms.