Have you tried one of the mold test kits from Home Depot?  It is a plastic petri dish with a nutrient-rich gel that will allow any floating mold spores to land and take root.  Well, EVERY HOME will always test positive with that test.  And that is because mold spores are everywhere.  So, that homes mold test kit is pretty much worthless.  

Testing for mold is simple in some cases, and difficult to accomplish in other cases.  So, we rely on an extensive visual inspection, years of experience, and some of the best testing equipment available.  In the end, we can find or rule out mold as a serious problem.

The example petri dish shows that a few mold spores landed on the gel and started to grow.  So, what does that mean.  Is there an active mold threat in the home, or is this normal?  After all, mold spores a free-floating in nearly every building.  They don't mean much unless they are the result of one or more active colonies of mold hiding somewhere.

The NUMBER of mold spores tell us more.  So, we use particle meters for real time mold testing, then we use moisture detection to locate potential mold problem.