Very difficult to test Hid systems.It is possible to check input power to the main ballast unit,usually located below the headlight,but output to the bulb is around 20kv strike voltage.Works a bit like a coil ignition system.Easy way is to swap parts from the other side headlight,but with 2 in trouble,that makes things more difficult.On some cars ,there are more gubbins inside the headlight that are not reachable or replaceable as individual parts.