In V-model different documents are required to conduct 
testing.

Testing phase                         Document
User Acceptance                       BRS
System Testing                        SRS
Integration Testing                   Design Document
Unit Testing                          source code

BRS:Business Requirement Specification
SRS:Software Requirement Specification

their r seven types is their.
1.Analysis phase review
2.Design phase review
3.Unit testing
4.Integration testing
5.System testing
6.User acceptance testing
7.Maintaince phase testing

Analysis phase review:
                   During this test reviews r conducted on 
 the design documents BRS,FRS,Project plan, etc
Design phase review: 
                   The reviews r conducted on the design
document to design the document as per the customer
requirement the logic,the design is understandable,the
design is good, coding also reviewed.
Unit testing:This test is conducted by the developer or
white box test engineer.
            it test single peace of code or component .this
test is conducted based on the code written by the developer.
their four steps in Unit testing
1.Statement coverage
2.Loop Coverage
3.Branch coverage
4.Functional Coverage
Statement Coverage:
        It is to be ensured each statement is executed
minimum one time.to validate the correctness
Loop Coverage:verify the loop statement like
while,for.....and other statements r working correctly r 
no.