How is an on ground lightning strike test conducted? Whenever a design company is obtaining an STC for an aircraft (Supplemental Design Certificate) for an electrical installation, one of the required tests to obtain the STC is a lightning strike test. The test is needed to show that the electronics installed can withstand a lightning strike without degrading their performance or inducing degradations into other systems. 

We can't position the aircraft on ground waiting for a lightning bolt to hit like 'Doc' in 'Back to the Future', so how do design companies, or engine manufacturers, etc. simulate a lightning strike and draw conclusive results that the system with withstand actual lightning?
You create your own lightning. You can do that with an impulse generator. Here's what a smaller one looks like:



I don't know if that's what is used for the certificates but it certainly one way to test against lightning strikes (provided that you can generate a high enough voltage).