Unit Test cases
The responsible people for the Unit Test cases are the 
programmers. Are they able to test and find defects for the 
product they developed? The Answer would be Yes and No. 
Because when the developer created his module obviously he 
will think that his work will always be correct and he will 
not be able to visualize the defects. Hence there is chance 
for the programmer to skip the unit test cases and 
execution. But if properly the Unit test cases are written 
and executed the defect ration will come down drastically 
and the Testers will be able to concentrate on the Black 
box.

The Good Unit Test cases are hard to write and time 
consuming. The developers have to spend time to write such 
effective unit test cases similar to writing Code. Poor 
Unit test cases will also prove the efficiency and 
understanding of the requirement by the developers. Not all 
developers who are good in writing code are good in writing 
Test cases. 

Writing Unit test cases is a skilled task and which is the 
basic testing done before the code is delivered to the 
quality. Hence more attention should be given in writing 
Unit Test cases.

Integration Testing

A project may have many modules. Not all modules are worked 
together. Certain modules are covered in first iteration 
and remaining is in forth coming iterations. When one 
module is completed it should be integrated with other 
modules. If the project is small in size the system are 
assembled and the integration will happen at the end. 

The integration testing will be performed on multiple 
environments also. Some times the client may user different 
environment and the solution provider may have a different 
one. At that time the integration process is a must. 
Usually the integration testing is conducted in parallel 
with the Unit Testing.