public function testSquareColor()
{
$chess = new Chess();
$this->assertSame($chess->squareColor('a1'), 'dark');
$this->assertSame($chess->squareColor('b2'), 'dark');
$this->assertSame($chess->squareColor('b3'), 'light');
$this->assertSame($chess->squareColor('e4'), 'light');
$this->assertSame($chess->squareColor('e5'), 'dark');
$this->assertSame($chess->squareColor('aw'), null);
}
