Testing Definitions - Part 3

what is the purpose of test plan?what are the key featuresto be mentioned  in test plan ?

A Test Plan gives detailed testing information, including
Scope of testing
Schedule
Test Deliverables
Release Criteria
Risks and Contingencies
and also includes the Test Strategy.

In practice, a Test Strategy is a subset of a Test Plan, if a Test Plan is formalized.

What is the integration testing ? explain it .

Integration Testing :  Integration testing is a logical extension of unit testing.
It could be in any format like between 2 or more modules / Units / Softwares / Environemnts / System Components..
Integration testing has to be repeated for each change/version that has been effected one of the object in the environement until it is specified as completely individual.

 
There are 3 types of Integration testings
1) COTS (Component Off The Shelf Testing).
2) Software Integration.
3) System Integration.
 
COTS : - It is done by the developer it checks the interface between the modules/functions.

Software Integration : It can be done by developer/tester If it is done by tester it'll be checking the interface between tow diffrent modules/software. How the data are transfering means integrity of data.
 
System Integration : It is done by tester it checkes the interface b/w tow diffrent system/software components.

What is tracibility Matrix? Does a test paln consists of/ What is the use of tracebility amtrix and when is it used?

Traceability matrix is helpful to trace a defect to requirements . Also it gives info whether all the requirements are covered in the Testcases.

It could be a part of the Testplan and depends on how you defined the Testplan Template for your Organization. Else u could have a separate document.

Requirements and corresponding testcases are plotted in X and Y-Axis. The cell (Testcase and Requirement
Cross Section) can have a value 'Y' (if Traceable) and 'N' (Not Traceable).