setUp/tearDown (@Before/@After) why we need them in JUnit?

Question

I believe that we are all know that setUp (@Before) will execute before any test method and tearDown(@After) will execute after test method.

Also we know that Junit

Answer 1

A custom runner such as SpringJUnit4ClassRunner may need to run some codes between the constructor and @Before method. In this case, the runner may inject some dependency which the @Before methods needs. But dependency injection can only be run after the object is constructed.