JUnit: using constructor instead of @Before

Question

I\'m using JUnit 4. I can\'t see the difference between initializing in the constructor or using a dedicated init function annotated by @Before. Does this mean

Answer 1

There is one thing that constructor can archive but not @Before.

You have to use a constructor when you need to initial fields defined in parent class. For example:

abstract class AbstractIT {
   int fieldAssignedInSubClass;
   public AbstractIT(int fieldAssignedInSubClass) {
      this.fieldAssignedInSubClass= fieldAssignedInSubClass;
   }

   @Before
   void before() {
      // comsume fieldAssignedInSubClass
   } 
}

public class ChildIT extends AbstractIT{
   public ChildIT() {
      // assign fieldAssignedInSubClass by constructor
      super(5566); 
   }

   @Before
   void before() {
      // you cannot assign fieldAssignedInSubClass by a @Before method
   } 
}