QA,QC AND TESTING are closely related, but they are 
different concepts.

These three are useful in manageing the risk of the 
developing and managing software.  

Quality Assurance: A set of activities designed to ensure 
that the development and/or maintenance process is adequate 
to ensure a system will meet its objectives.
 
Quality Control: A set of activities designed to evaluate a 
developed work product. 

Testing: The process of executing a system with the intent 
of finding defects. 

QA activities ensure that the process is defined and 
appropriate.
 
QC activities focus on finding defects in specific 
deliverables.
 
Testing is one example of a QC activity, but there are 
others such as inspections

Testing therefore is product oriented and thus is in the QC 
domain