To provide a testing device and a technique for testing a protection device appropriately.

A testing device 900 tests a communication control unit 10 functioning as a protection device for protecting attack to a communication device. The testing device 900 comprises: an output section 904 for outputting data to the communication control unit 10; a holding section 950 for correlating data outputted to the communication control unit 10 to data outputted from the communication control unit 10 for holding; an input section 906 for inputting data outputted from the communication control unit 10; an inspection section 908 for inspecting whether the communication control unit 10 is operating normally; and an update section 952 for updating data held by the holding section 950 following the update of databases. The output section 904 selects the data of a record updated by the update section 952 from among data held by the holding section 950 for outputting it to the communication control unit 10.