Bugs love places to hide. This is true for software bugs as well. Likely the single best deterrent of software bugs is clean code design.

Likely bug injection points include:

  1. Incorrect or failed processing of certain test cases.
  2. Incorrect or failed processing for null test cases.
  3. Adding new or changing functionality.
  4. Failure to validate input data or to maintain data integrity.
  5. Failure to follow SRP.