A testing apparatus employs an interface module removably attached to a filter testing device. The interface module includes a first flowpath communicating with an outlet of the testing device and a housing of the filter device, a first valve disposed in the first flowpath, a second flowpath communicating with the housing of the filter device and an exhaust, a second valve disposed in the second flowpath, and an enclosure enclosing the first flowpath, the first valve, the second flowpath, and the second valve. The interface module is cleanable and/or sterilizable, and replaceable. A filter integrity testing method uses an interface module to prevent contamination of the testing device and cross-contamination of different filter devices and avoid liquid ingress into the testing device.