A test cylinder of a valve assembly is mounted a body of the valve assembly, the body includes a holder containing an accommodation chamber, a bottom fence formed, and a cold-water inlet and a hot-water inlet which respectively communicate with a cold-water inflow pipe and a hot-water inflow pipe of the body. The accommodation chamber has a first mixing-water outlet and a second mixing-water outlet which individually communicate with a first outflow pipe and a second outflow pipe. The test cylinder includes a peripheral fence, a first orifice, an edge fence, and a first cavity defined. The peripheral fence has at least one second orifice, a second cavity, and an internal surround portion of the accommodation chamber. The edge fence has a closing portion extending from an outer wall thereof and has a conduit defined in the edge fence.