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 . <EOS>