Testing for faulty airbags is usually built into the battery of electronic tests that your technician performs when you bring your car in for a regular service and inspection. Let’s face it. You cannot actually test for faulty airbags by whacking the front bumper with enough force to cause airbag deployment for two reasons. The first is that deployment of an airbag in anything other than an accident can cause huge damage to your car’s interior. The second is that replacing a deployed airbag, even if allowed by your state’s DMV, is largely expensive. This means you will have to rely on electronic testing, rather than the real thing.
For more info, see The Dangers of Car Airbags