These tests can be classified under two broad categories. Those which test the stability of the product and those that test the stability of the product from external forces. In the first group you will find elevated temperature, freeze-thaw, evaporation, stability with packaging, and stability with labels.
External testing includes resistance to attack by microorganisms, UV radiation, and oxygen.
In cosmetics, only antimicrobial testing is required by law. The chemistry of common anti-oxidants, preservatives, and UV absorbers, along with how to formulate for each type, is covered. A realistic battery of stability tests is also reviewed, which will indicate the stability of a product and the rationale for its use.