Which of the following is the BEST way to ensure that an application is performing...

Integration testing is the best way to ensure that an application is performing according to its specifications, because it tests the interaction and compatibility of different modules or components of the application. Unit testing, pilot testing and system testing are also important, but they do not cover the whole functionality and integration of the application as well as integration testing does. References: CISA Review Manual (Digital Version)1, Chapter 4, Section 4.2.3