Checking ignition secondary is difficult first because there are several different kinds of secondary voltage distribution system and because failures don't always occur under all conditions.
Older distributor systems, whether they used points or some type of electronic trigger, can have many different failure modes. About the only tool that you can use to catch them all is the old Sun Ignition Analyzer Scope. I had a car back in the 70s that would miss/backfire/run crappy during damp weather. New point, rotor, cap, wires and plugs helped but did not cure it. I only found the root problem when I ran the engine in a completely darkened garage and sprayed a light mist of water on the cap and wires. Turns out there was a carbon arc trail from the coil center tower to the bracket holing the coil that would provide a path to ground when damp.
If you have a coil pack, you can possibly have internal shorts. With COP, you can not get to the secondary while it is on the engine.
Check resistance and even impedance on both the primary and secondary will not always show an issue. If you can access the PRIMARY control wire a simple inductive pickup will give you a lot of info from the back EMF if you know what you are looking for.
Same is true for injectors, but a partially clogged injector may still have a "good" signature.