Exposing the instantiation of an inner context for testing.

.java

public class Enclosing {

   public String methodA() {
     getContext();
     ......
   }

   protected void getContext() {
     Inner.getContext();
     ......
   }
  
 @Test
public void test_something() {
    Enclosing enclosing = new Enclosing() {
        @Override
        protected void getContext() {
            // do what you need here
        }
    };

  // your test code on enclosing where you control getContext
}