public void TestIncreaseRevsSpeedLessThan40()
        {
            ISeacraft seabird = new Seabird();

            seabird.IncreaseRevs();
            seabird.IncreaseRevs();
            Assert.IsFalse(((IAircraft)seabird).Airborne);
            Assert.AreEqual(0, ((IAircraft)seabird).Height);
            Assert.AreEqual(20, seabird.Speed);
        }
        public void TestIncreaseRevsSpeedGreaterThan40()
        {
            ISeacraft seabird = new Seabird();

            seabird.IncreaseRevs();
            seabird.IncreaseRevs();
            seabird.IncreaseRevs();
            seabird.IncreaseRevs();
            seabird.IncreaseRevs();
            Assert.IsTrue(((IAircraft)seabird).Airborne);
            Assert.AreEqual(100, ((IAircraft)seabird).Height);
            Assert.AreEqual(50, seabird.Speed);
        }