public function testBin()
{
$creditCard = new CreditCard("1234560011112222", "12/2018", "999");
$this->assertEquals("123456", $creditCard->bin());
}
public function testBin()
{
$creditCard = new CreditCard("1234560011112222", "12/2018", "999");
$this->assertEquals("123456", $creditCard->bin());
}