Testing Stripe payment (checkout) using Codeception

PayByStripeCept.php

<?php

/**
 * Codeception acceptance test for testing Stripe payments (Checkout)
 *
 * NB: I'm using lowercase variable for the Actor object ($i) instead of $I
 */

// replace these values
$initialPage = '';
$ccNumber = str_split('4242424242424242'); // convert the string to array, see below why
$expiry = str_split('1120');
$cvc = str_split('123');
$ccLength = count($ccNumber);
$expiryLength = count($expiry);
$cvcLength = count($cvc);

// since the input ids are dynamic and they don't have a 'name' attribute,
// I'm using the placeholder attribute which uniquely identifies the field
$fieldCard   = 'input[placeholder="Card number"]';
$fieldExpiry = 'input[placeholder="MM / YY"]';
$fieldCvc    = 'input[placeholder="CVC"]';

$i = new AcceptanceTester($scenario);
$i->wantTo('pay by using Stripe');

$i->amOnPage($initialPage);
$i->maximizeWindow();
$i->see('Payment summary');

// wait until Stripe's 'Pay by Card' button appears and is clickable
$i->waitForElementVisible('.stripe-button-el');
$i->click('.stripe-button-el');

// wait a bit for the popup to appear
$i->wait(2);

// it's an iframe, let's switch to it
$i->switchToIFrame('stripe_checkout_app');
$i->waitForElementVisible('input[type="email"]');

// enter the email address
$i->fillField('input[type="email"]', 'test@example.org');

// can't use the fillField() method here because it messes up the input value
// iterate through the arrays containing the characters
for ( $k = 0; $k < $ccLength; $k++ )
    $i->appendField($fieldCard, $ccNumber[$k]);

for ( $k = 0; $k < $expiryLength; $k++ )
    $i->appendField($fieldExpiry, $expiry[$k]);

for ( $k = 0; $k < $cvcLength; $k++ )
    $i->appendField($fieldCvc, $cvc[$k]);

// submit form
$i->click('button[type="submit"]');

// success page or message
$i->waitForText('Thank you for your order', 20);