Test methods are of two broad categories: chemical tests (e.g., for vitamins or pesticides) and microbiological tests (e.g., for spoilage agents or biological threat agents). Before a given method can be approved as an AOAC official method, it is peer reviewed and tested in 8–10 laboratories in what is called a "Collaborative Study". The findings are often published on the Journal of AOAC International.[5][6][3]