// Initialize a new card:
card := creditcard.Card{Number: "4242424242424242", Cvv: "11111", Month: "02", Year: "2016"}

// Retrieve the card's brand (which credit card company this card belongs to)
err := card.Brand() // card.Brand({Code: "visa", Name: "Visa"})

// Display last four digits
lastFour, err := card.LastFour() // 4242

// Validate the card's number (without capturing)
err := card.Validate() // will return an error due to not allowing test cards

err := card.Validate(true) // this will work though