INTEGRATION TESTING ● After or during Unit Testing ● Putting modules together in a controlled way to incrementally build up the final system. ● Start with a hierarchy of modules. ● Write Stubs and Drivers as needed.

HIERARCHY A B CD E F G COPY DOWN

BOTTOM-UP Test E Test F Test G Test B,E,F Test C Test D,G Test A,B,C,D, E,F,G

Bottom-Up Testing ● No need for Stubs. ● Useful when many of the low-level components are general-purpose utility routines that are invoked often by others. ● Useful for object-oriented design. ● Major system functionality tested last!

TOP-DOWN Test A Test A,B,C,D Test A,B,C,D, E,F,G

Top-Down Design ● No need for Drivers. ● Test main functionality early. ● More stubs than drivers. ● Stubs are usually harder to write. ● May find some timing problems (low level modules) late in the testing cycle.

Modified Top-Down Test A B C D A,B, C,D E F G A,B,C, D,E,F

Modified Top-Down ● Reduces the number of stubs. ● Some drivers are needed to test each module separately.

BIG-BANG Test A B C D E F G A,B,C,D, E,F,G

BIG BANG ● Most programmers use this method. ● Somewhat practical for small systems. ● Not practical for large systems. ● Requires both stubs and drivers. ● It's difficult to find failures. ● Interface faults cannot be distinguished easily from other types of faults.

SANDWICH Test AGA F E D,G B,E,F A,B,C,D, E,F,G

SANDWICH ● Combines a Top-Down and a Bottom-Up approach. ● System is viewed as three layers, just like a sandwich (the target layer in the middle, the levels above and below). ● Testing converges on the target layer. ● Stubs for utilities need not be written. ● Does not test the individual components throroughly

MODIFIED SANDWICH Test AGA F E D,G B,E,F A,B,C,D, E,F,G C D B Test

MODIFIED SANDWICH ● Allows upper-level components to be tested before merging them with others.

Comparison of Integration Strategies Handout