title: Unit testing in Java - what is it?
body: <p>Can you explain in a few sentences:</p>
  
  <ol>
  <li>Why we need it / why they make our life easier ?</li>
  <li>How to unit-test [simple example in Java] ?</li>
  <li>When do not we need them / types of projects we can leave unit-testing out?</li>
  <li>useful links</li>
  </ol>