add flight throws RuntimeException when null or negative duration

src/test/java/hs/fulda/de/ci/exam/project/AdminTest.java

@@ -86,6 +86,23 @@ public class AdminTest {
         });
     }
 
+    @Test
+    public void shouldThrowRuntimeExceptionWhenNull(){
+
+        assertThrows(RuntimeException.class, () -> {
+            admin.addFlight(null, airport_fr, airport1_ist, 140);
+        });
+        assertThrows(RuntimeException.class, () -> {
+            admin.addFlight("1", null, airport1_ist, 140);
+        });
+        assertThrows(RuntimeException.class, () -> {
+            admin.addFlight("1", airport_fr, null, 140);
+        });
+        assertThrows(RuntimeException.class, () -> {
+            admin.addFlight("1", airport_fr, airport1_ist, -40);
+        });
+    }
+
 
 
 }