There is no proper answer of this question.Actuallly it 
varies with circumstances and condition on which you are 
testing and totally depends upon the requirements provided 
by the users and according to your project delivery 
deadline.

1.once Base documents like BRD ready, based on that FRD will
be prepared and individual functionalities  will be
identified and prioratized and those documents will be
circulated to both development team , understanding the
functional requirement the development team starts coding
and parallely testing team will prepare test cases.
2.There no exact answer like when to stop testing, testing
can be stopped at certain period like
  all the test cases should be executed.
  Pass percentage should be met.
  All major defects should be fixed and resolved.
  Schedule aspects and budget also considered here..