public function testAddition(array $polynomialA, array $polynomialB, array $expected_sum)
{
$polynomialA = new Polynomial($polynomialA);
$polynomialB = new Polynomial($polynomialB);
$expected = new Polynomial($expected_sum);
$sum = $polynomialA->add($polynomialB);
$this->assertEquals($expected, $sum);
}