I have heard the term "smoke test" as a diagnostic tool, but was not sure what it is for. Is it to measure the opacity of the vehicle exhaust or is it some sort of test to find air leaks into the passenger compartment?
The "Smoke Test" is the first time an electrical device is powered up and is when the device is checked for leaks.
It apparently first originates with Lucas electrical parts and wiring looms. Paul Lucas is also known as the Pince of Darkness and credited with inventing the short circuit.
Most early British cars use Lucas electrics and when these fail is usually because of an escape of smoke.
It is noted that once the smoke escapes the circuit no longer works and the logical conclusion is that smoke is a vital component and if lost must be replaced in order to restore functionality.
For Lucas electrics there is a replacement smoke kit available: