Connection device for connecting a pressurised container to a pressure test bench in a self-reinforcing embodiment, comprising: - a main component which is formed by a bottom component and a top component arranged on the bottom component, - a connection device formed on the top component of the main component for a connection to a pressurised container to be tested, - a further connection device formed on the bottom component of the main component for a connection to a pressure test bench, - a fluid supply line, which is formed for supplying a pressurised test fluid into the pressurised container to be tested, in the main component and which connects the connection device and the further connection device, wherein an inlet on the test bench side and an outlet on the pressurised container side of the fluid supply line are formed on opposing front faces (9, 10) of the main component, - a functional component which is displaceably arranged on the main component in a component receiver (16, 18) in the longitudinal direction of the main component, wherein the component receivers (16, 18) for receiving the functional component are formed with a lower receiving portion on the bottom component and an upper receiving portion on the top component, - a sealing ring made of resilient material which is mounted on the main component and bears against the functional component and - a further fluid supply line which is formed in the main component and which is configured in order to introduce an additional pressurised fluid into a functional space in the component receiver (16, 18), such that the functional component in the component receiver (16, 18) displaces the sealing ring by compression and at the same time a further functional space of the connection device is enlarged, the pressurised test fluid being able to flow therein for further pressurisation of the functional component and thus for further compression of the sealing ring, wherein the functional component is S-shaped with a central portion and opposingly angled-back portions in both end regions and wherein the functional component is pressed toward the inlet on the test bench side on the front face of the bottom component when the sealing ring is compressed in the component receiver (16, 18). - a main component which is formed by a bottom component and a top component arranged on the bottom component, - a connection device formed on the top component of the main component for a connection to a pressurised container to be tested, - a further connection device formed on the bottom component of the main component for a connection to a pressure test bench, - a fluid supply line, which is formed for supplying a pressurised test fluid into the pressurised container to be tested, in the main component and which connects the connection device and the further connection device, wherein an inlet on the test bench side and an outlet on the pressurised container side of the fluid supply line are formed on opposing front faces (9, 10) of the main component, - a functional component which is displaceably arranged on the main component in a component receiver (16, 18) in the longitudinal direction of the main component, wherein the component receivers (16, 18) for receiving the functional component are formed with a lower receiving portion on the bottom component and an upper receiving portion on the top component, - a sealing ring made of resilient material which is mounted on the main component and bears against the functional component and - a further fluid supply line which is formed in the main component and which is configured in order to introduce an additional pressurised fluid into a functional space in the component receiver (16, 18), such that the functional component in the component receiver (16, 18) displaces the sealing ring by compression and at the same time a further functional space of the connection device is enlarged, the pressurised test fluid being able to flow therein for further pressurisation of the functional component and thus for further compression of the sealing ring,