types of integeration testing:
top down
bottom up
Top down :
               testing hierarchy starts from higher level 
to lower level.if suppose testers dnt get the lower modules 
for testing(consider the lower modules are under developmnt)
wat the testers wil do thy wil place dummy modules and 
integerate these dummy modules with the higher level 
modules.in top down apparoach the dummy modules r called 
Stubs.
Stubs- Def
       stubs r the dummy modules tht simulates the low 
level modules.
Bottom up:
           in this the dummy modules r called drivers.
Drivers- Def:
         drivers r the dummy modules tht simulate the high 
level modules.

Integration testing: carrying out integration tests.

Integration tests (After Leung and White) for procedural 
languages. This is easily generalized for OO languages by 
using the equivalent constructs for message passing.  In 
the following, the word "call" is to be understood in the 
most general sense of a data flow and is not restricted to 
just formal subroutine calls and returns ? for example, 
passage of data through global data structures and/or the 
use of pointers.

    Let A and B be two components in which A calls B.
    Let Ta be the component level tests of A
    Let Tb be the component level tests of B
    Tab    The tests in A's suite that cause A to call B.
    Tbsa  The tests in B's suite for which it is possible 
to sensitize A -- the inputs    
     are to A, not B.
    Tbsa + Tab == the integration test suite (+ = union).