public void ShouldNotThrowExceptionWhenValid()
            {
                var action = new ImagemapMessageAction()
                {
                    Text = "test",
                    Area = new ImagemapArea(1, 2, 3, 4)
                };

                action.Validate();
            }
            public void ShouldThrowExceptionWhenAreaIsNull()
            {
                var action = new ImagemapMessageAction()
                {
                    Text = "test"
                };

                ExceptionAssert.Throws <InvalidOperationException>("The area cannot be null.", () =>
                {
                    action.Validate();
                });
            }
            public void ShouldThrowExceptionWhenTextIsNull()
            {
                var action = new ImagemapMessageAction()
                {
                    Area = new ImagemapArea(1, 2, 3, 4)
                };

                ExceptionAssert.Throws <InvalidOperationException>("The text cannot be null.", () =>
                {
                    action.Validate();
                });
            }