title: DataJpaTest annotation usage[Spring-boot]
body: <p>what is the usage of @DataJpaTest annotation when testing ?
  do we need it with every db connecting test?</p>
  
  <p>the test is working even without the annotation</p>
  
  <pre><code> @RunWith(SpringRunner.class) 
   @DataJpaTest
  </code></pre>
  
  <p>why @DataJpaTest is used why it has used and when to use it?</p>