public void Test_SetBONull() { //---------------Set up test pack------------------- Car bo = new Car(); BOStatus status = new BOStatus(bo); //---------------Execute Test ---------------------- try { status.BusinessObject = null; Assert.Fail("expected ArgumentNullException"); } //---------------Test Result ----------------------- catch (ArgumentNullException ex) { StringAssert.Contains("Value cannot be null", ex.Message); StringAssert.Contains("value", ex.ParamName); } }