Catalase is the enzyme that breaks hydrogen peroxide (H2O2) into H2O and O2. Hydrogen peroxide is often used as a topical disinfectant in wounds, and the bubbling that is seen is due to the evolution of O2 gas. H2O2 is a potent oxidizing agent that can wreak havoc in a cell; because of this, any cell that uses O2 or can live in the presence of O2 must have a way to get rid of the peroxide. One of those ways is to make catalase.
You can find the test protocol here.