The two types of scalability tests done in performance testing are:
Upward scalability test: This kind of test refers to one in which the number of users of the system is increased on a particular scale, up until the system gets to a crash point. The essence of doing this test is to enable us to find the maximum capacity of the application in question.
Downward scalability test: This is the test carried out when load testing is not passed. This test involves reducing the numbers of users for a system until a set goal is achieved, this reduction would enable us to find at what point congestion starts and where system limits lie.