Integration is an essential characteristic of any network, database or assembled set of interacting systems. The human brain is a collection of many small, relatively simple units (neurons), which produces complicated results through the interaction of its parts. An individual neuron cannot do much; it cannot even survive on its own but it is connected with thousands of other neurons. It is their integration that gives neurons their collective power.

Integration testing is the process of ensuring that components fit together and work together correctly, after they have been shown to work individually by unit testing. For example, the client-based queries in a system need to work correctly with the remote server data bases. The art of integrating together components, applications or systems is a complex one. There are many possibilities for incompatibility and interference among the components, leading to the need to test their integration. The term "integration" means different things to different people and the testing of all these types of integration will be discussed in this class.