Essentially yes.
there are basically 2 kinds if spark testers. Neon in-line and gap. Each can tell you different things. Neither will tell you the condition of a spark plug. There are internet rocket scientists on utube showing using an ohm meter to measure resistance and then proclaiming a plug good or bad. These people haven't got a clue. If you really need to test a 3 dollar spark plug you need a macine that puts it under pressure and high voltage.
Aviation Spark Plug Testers 110V And 220V Designed to clean and test all 14mm & 18mm massive and fine-wire electrode aviation sparkplugs.
www.aircraftspruce.com
You would be suprised how many machines i get in the shop that won't run or runs pooly and the only problem is the spark plug.