A device for testing a fluid including an elongated carrier; two foam members for absorbing the fluid, which are arranged at an end of the carrier; a positioning member having a sleeve which is slidably arranged on the carrier; and a diagnostic device, which is arranged in the positioning member having a sensor die adapted to detecting at least one property of the fluid and means for supplying the fluid to a sensor surface of the sensor die. After the fluid has been supplied to the foam members, the positioning member is moved towards the end of the carrier where the foam members are located. When the diagnostic device comes into contact with one of the foam members, the fluid is squeezed from the foam member and supplied to the sensor surface of the sensor die through the fluid supplying means of the diagnostic device.