This website is dedicated to providing a archive of all performance tests done in and around the game Factorio. The goal being to maximize the size of the factory without succumbing to performance costs.
A good example of a hardware test is to benchmark a map while at stock CPU frequency and then to benchmark that same map when overclocked. Hardware tests can enable us to better model our ingame tests to be most representative of actual megabase gameplay.
As for ingame tests, these are tests in which we compare designs in the actual game. We can set a targeted production rate and scale each design to meet or exceed that target. There are an extreme variety of designs possible, thus these type of tests will tend to fall into two different types of tests. Firstly, comparing radically different designs A and B to gauge on a fundamental level which designs are more UPS efficient. The second usual type of ingame test is testing design A1 versus design A2. These tests take the same essential design and modify a small part of it. This tells us the inherent efficiencies of each fundamental design element. An example of the first tendency ingame tests have is testing an oil build with coal liquefaction versus advanced oil processing. A good second tendency test is testing inserters swinging all the time against using the circuit network to control how often they swing.
A general testing guidelines document can be found here.