A testing assembly for a drug delivery device is disclosed. The testing assembly can include a pressure vessel having a sealed pressure chamber that is configured to be pressurized to a predetermined pressure. The pressure vessel further defines an injection opening extending from an exterior thereof to the pressure chamber. A pierceable barrier extends over and seals the injection opening. The testing assembly further includes a measurement device disposed within the pressure chamber and a container aligned with the injection opening, such that the container is configured to collect a dose of a drug delivered via a drug delivery device through the pierceable barrier and the measurement device is configured to measure the dose of the drug.