How can I test reaction time? How can I measure someone's ability for the speed to which they react to something? Is their a way to test something like a person's reaction timing that doesn't involve something as simple as the ruler test, but rather something a bit more complex.

Edited: The ruler test: https://www.youtube.com/watch?v=yn6WRm6TiPk
I have not yet done initial research on this topic because I want some good opinions on sources that I can use to better my understanding of this topic. I apologize if I was not clear at first.
It is very typical to record response times. Usually using a computer keyboard. It's easy to program or some software can do it for you (e.g. e-prime). You can also use already-made response boxes (e.g. RTbox), or make your own (e.g. with an arduino). As pointed out, it is usually good to control for performance to prevent speed-accuracy tradeoff confounds.

Li, X., Liang, Z., Kleiner, M., &amp; Lu, Z. L. (2010). RTbox: a device for highly accurate response time measurements. Behavior Research Methods, 42(1), 212-225.

Schubert, T. W., D’Ausilio, A., &amp; Canto, R. (2013). Using Arduino microcontroller boards to measure response latencies. Behavior research methods, 45(4), 1332-1346.