How to PROPERLY test that your smoke detectors work?
Proper test methods depend on type, as there are different technologies employed depending on model. Some use a photo-sensitive element to "see" smoke, others use a radioactive element to detect products of combustion (even invisible ones), others "see" flames with an infrared detector and others detect heat.

You should test them exactly according to manufacturer's instructions and if they do not perform then replace them immediately. Like any other consumer product, you should deal with the seller and/or supplier and manufacturer for grievances related to defective products.

Exercise your right not to buy crap products and you will end up with reliable smoke/fire/CO detectors.