Add more test cases

Author: tamasvajk

java/ql/test/query-tests/EmptyMethod/EmptyMethod.expected

@@ -1 +1,3 @@
 | Test.java:13:15:13:16 | f2 | Empty method found. |
+| Test.java:27:17:27:17 | f | Empty method found. |
+| Test.java:32:18:32:23 | method | Empty method found. |

java/ql/test/query-tests/EmptyMethod/Test.java

@@ -21,4 +21,15 @@ public abstract class TestInner {
     public abstract void f();
   }
 
+  public class Derived extends TestInner {
+
+    @Override
+    public void f() { } // $ Alert
+  }
+
+  public interface TestInterface {
+
+    default void method() { } // $ Alert
+  }
+
 }