public void Constructor_Valid_SetToSpaceCharacter()
        {
            // Arrange

            // Act
            var TestSquare = new TicTacToeGridSquare();

            // Assert
            Assert.AreEqual(' ', TestSquare.CurrentMark);
        }
        public void SetCurrentMark_SetToInvalidType_ThrowsException()
        {
            // Arrange
            var TestSquare = new TicTacToeGridSquare();

            // Act
            TestSquare.CurrentMark = 'd';

            // Assert -- exception was thrown
        }
        public void SetCurrentMark_SetToO_ReturnsXMark()
        {
            // Arrange
            var TestSquare = new TicTacToeGridSquare();

            // Act
            TestSquare.CurrentMark = 'O';

            // Assert
            Assert.AreEqual('O', TestSquare.CurrentMark);
        }
        public void SetCurrentMark_SetToXAndBackToSpace_ReturnsSpace()
        {
            // Arrange
            var TestSquare = new TicTacToeGridSquare();

            TestSquare.CurrentMark = 'X';

            // Act
            TestSquare.CurrentMark = ' ';

            // Assert
            Assert.AreEqual(' ', TestSquare.CurrentMark);
        }