The Need of Unit Testing:a) Unit testing gives programmers measurable confidence in the source code they produce.
b) Unit testing uncovers defects in source code shortly after it is written, which saves valuable time and resources, sometimes by orders of magnitude.
c) Unit testing significantly reduces the amount of debugging necessary by avoiding defects in the first place and by catching those that do occur while they are relatively easy to detect and fix.
d) Unit testing avoids the practice of testing everything at once when it is significantly more expensive in terms of cost, development team morale, and customer satisfaction.
e) Unit testing helps you focus on exactly what is important for a module so that when all of your tests run successfully, you can be reasonably sure that your module has no major defects.