Common factors in deciding when to stop Testing:

  1. Show stoppers encountered
  2. Too many minor bugs pending to be fixed
  3. Deadlines (release deadlines, testing deadlines, etc.)
  4. Test cases completed with certain percentage passed
  5. Test budget depleted
  6. Coverage of code/functionality/requirements reaches a specified point
  7. Bug rate falls below a certain level
  8. Beta or alpha testing period ends

All this depends and varies from organization to organization. But these are the general factors to take into consideration. If you want to add anything, let us know by making a comment below.