A foam test is not a valid laboratory test, also a smell test is not either. Depending on what you eat and drink can determine the amount of foam (if at all) or smell (if at all). Drink a lot of beer --- foam and no smell, eat a lot of asparagus --- terrible smell and a lot of foam. drink a whole lot of water and eat nothing but vegetables --- no foam and no smell. No foam can flag it for more testing, but it cannot be used for an actual failure. They have to find some actual chemical reason to fail a person. Something that can be put into writing and specific levels can be read. So far there is no scale or level for the absence of smell and foam.