we are not going to develop test plan document. test lead is
going to prepare test plan documents.bottom up and top down
approaches are used for integration testing.in top down
approach we are connecting main module with submodules in
the place of remaining under constructive sub modules we
will use stubs. in bottom up approach in the place of under
constructive main module we will use a temporary program
call ed driver

k friends
subhan.k

the Test lead is preparing the test plan document and he is
scheduling that means how to test, what to test, who to test
and when to test.
BOTTOM-UP approach is, in this the main module will be under
construction, to conect the main module with submodule we
use a temperory programme called Drivers in the place of
Main module.
TOP-DOWN, in this approach the sub modules will be under
construction to connect this main module to sub modules we
use  temperory submodule called Stubs.
By using temperory programmes called Stubs(sub-module),
Drivers(main module) we connect the programmes.

Normally Test lead is preparing Test plan document but team
member May be involved in preparing Test plan document. 
This is the information given in the ISTQB Material.

WBS-Work Break down Structure is used to do scheduling which
holds the following information.

1. what to test, 
2. who to test
3. when to test.
By using WBS we can analyze whether we are going in the
right path or varying from the plan.

Test plan & schedule is prepared from following:

1. Historical data
2. If some similar project is currently under testing
3. SRS doc
4. Functional Specification Doc