State transition testing is useful for both procedural and object-oriented development. It is based on the concepts of states and finite-state machines, and allows the tester to view the developing software in term of its states, transitions between states, and the inputs and events that trigger state changes. This view gives the tester an additional opportunity to develop test cases to detect defects that may not be revealed using the input/output condition as well as cause-and-effect views presented by equivalence class partitioning and cause-and-effect graphing. Some useful definitions related to state concepts are as follows:

A state is an internal configuration of a system or component. It is defined in terms of the values assumed at a particular time for the variables that characterize the system or component.

A finite-state machine is an abstract machine that can be represented by a state graph having a finite number of states and a finite number of transitions between states.