Integration is a systematic approach to build the complete software structure specified in thedesign from unit-tested modules. Integration testing identifies problems that occur when unit arecombined. By using a test plan that requires testing each unit and ensuring the viability of eachcombining units, any errors discovered when combining units are likely related to the interface betweenunits. It is a logical extension of Unit testing. The integration plan describes the sequence ofintegration, overhead software, test environment and resources required.