A multi-stage, oral-fluid collection and testing device for collecting and testing an oral-fluid for substances, the testing device comprising: a body assembly and a cap assembly, the body assembly including: a collection sponge for absorbing an oral fluid received from a donor, a test strip for receiving the oral fluid and presenting a visual indicator indicating presence of a predetermined substance, a body portion securing the collection sponge and the test strip and defining a fluid reservoir and a test strip channel, the test strip located in the test strip channel; and the cap assembly including: a cap having a first closed end and a second open end, and configured to receive a portion of the body assembly, the cap defining a cap cavity; a fluid container having a sealing membrane and containing a fluid for mixing with the oral fluid, the fluid container housed within the cap cavity, and a plunger defining a fluid channel; characterized by the fact that the plunger has a penetrating tip and is axially slidable within said cap, the penetrating tip of the plunger being initially positioned at the sealing membrane, such that, when the cap assembly receives a cap-engagement portion of the body assembly in a first engagement position, the plunger slides towards the fluid container, thereby causing the penetrating tip of the plunger to pierce the sealing membrane of the fluid container which in turn causes a first-stage fluid flow and releases the fluid contained in the fluid container for mixing onto the collection sponge. a body assembly and a cap assembly, the body assembly including: a collection sponge for absorbing an oral fluid received from a donor, a test strip for receiving the oral fluid and presenting a visual indicator indicating presence of a predetermined substance, a body portion securing the collection sponge and the test strip and defining a fluid reservoir and a test strip channel, the test strip located in the test strip channel; and a collection sponge for absorbing an oral fluid received from a donor, a test strip for receiving the oral fluid and presenting a visual indicator indicating presence of a predetermined substance, a body portion securing the collection sponge and the test strip and defining a fluid reservoir and a test strip channel, the test strip located in the test strip channel; and the cap assembly including: a cap having a first closed end and a second open end, and configured to receive a portion of the body assembly, the cap defining a cap cavity; a fluid container having a sealing membrane and containing a fluid for mixing with the oral fluid, the fluid container housed within the cap cavity, and a plunger defining a fluid channel; a cap having a first closed end and a second open end, and configured to receive a portion of the body assembly, the cap defining a cap cavity; a fluid container having a sealing membrane and containing a fluid for mixing with the oral fluid, the fluid container housed within the cap cavity, and a plunger defining a fluid channel; characterized by the fact that the plunger has a penetrating tip and is axially slidable within said cap, the penetrating tip of the plunger being initially positioned at the sealing membrane, such that, when the cap assembly receives a cap-engagement portion of the body assembly in a first engagement position, the plunger slides towards the fluid container, thereby causing the penetrating tip of the plunger to pierce the sealing membrane of the fluid container which in turn causes a first-stage fluid flow and releases the fluid contained in the fluid container for mixing onto the collection sponge.