Challenge tests are laboratory tests in which a known number of microorganisms (such as Listeria monocytogenes, Salmonella, Bacillus cereus, yeasts or moulds) are deliberately added to a food product. The product is then stored under realistic storage conditions (such as temperature, packaging and time) to observe whether and how quickly the microorganism grows, survives or dies. The aim is to assess the microbiological safety or shelf life of a specific product in its actual matrix and packaging. Challenge tests are best known in the context of Listeria control, but they have many other applications and advantages.