In one embodiment, a modular dissolution-testing apparatus has a base unit adapted to hold and control operation of between one and eight dissolution-testing modules. The base unit has a programmable controller and a color touch screen for user interface with the controller and the modules. Each module includes a vessel for holding a solution of a dosage form dissolving in a solvent, an agitator apparatus for stirring the solution, and a motor to power—via a multi-motion assembly and a stirring shaft—stirring by, lifting of, and lowering of, the apparatus. Each module has a vessel heater and a temperature sensor, both communicatively connected to the controller for heating and regulating the temperature of the vessel contents. Each module is independently controllable by the controller, where control includes manually (by a user) or programmatically setting stirring speed, lifting and lowering apparatus, and starting and stopping stirring and heating.