A payment gateway is an IT system that mediates the authorization and processing of electronic payments between online stores and financial institutions. It connects customers, merchants, banks, and card organizations, ensuring secure transmission of payment data and transaction verification. Modern payment gateways handle diverse payment methods – from traditional credit and debit cards, through BLIK and bank transfers, to modern digital wallets like Apple Pay or Google Pay. Their role is not only to process payments but also to protect sensitive financial data in accordance with the highest security standards.

In SaaS applications, payment gateways play a particularly crucial role, handling recurring payments, automatic subscription renewals, different pricing plans, and multi-currency settlements. A payment system failure in SaaS means not only losing new conversions but can also disrupt subscription renewal cycles, directly impacting Monthly Recurring Revenue (MRR) and long-term customer value.

What Threats Do Payment Gateways Face?

Payment gateways, as key elements of e-commerce infrastructure, are particularly vulnerable to various threats:

Technical threats include system overloads during heavy traffic, hardware failures (drives, servers, network components), integration problems between different systems, and application code errors. Inadequate architecture can lead to cascading failures of the entire payment system.

Security threats primarily involve hacker attacks – from system breach attempts, through DDoS attacks aimed at paralyzing the service, to card data theft attempts. Particularly dangerous are man-in-the-middle attacks, where criminals intercept communication between the customer and the payment system.

Regulatory threats relate to the necessity of complying with numerous regulations, such as PCI DSS for card data security, GDPR for personal data protection, or the PSD2 directive regulating payment services in Europe. Non-compliance with these requirements can result in high fines and license loss.

Why Is Payment Gateway Testing Crucial?

Testing payment gateways is an absolute necessity resulting from the critical role they play in the online sales process. Every payment system failure means immediate revenue loss, as customers cannot complete their purchases. Comprehensive testing allows identification of system weak points before they manifest in the production environment. This includes functional tests verifying correct processing of various payment types, performance tests checking system behavior under load, and security tests detecting potential vulnerabilities. Regular testing also helps maintain compliance with regulatory requirements. Security audits and penetration tests are often legal requirements, and conducting them protects against legal and financial consequences.

Payment Gateway Crises in History

History knows many payment gateway failures that show how costly testing negligence can be.

PayPal experienced a global outage in November 2024 that lasted about two hours and affected many of the company’s products. The outage impacted account withdrawals, express checkout, cryptocurrency functions, and several other features. Downdetector recorded a peak of problem reports at 8,735 reports. Users worldwide couldn’t log into their accounts, causing panic – many thought their accounts had been hacked.

Stripe, one of the world’s most popular payment gateways, also had its problems. In 2019, a several-hour outage caused thousands of online stores to be unable to process card payments. This was particularly painful for e-commerce companies in North America.

The Importance of Software and Hardware Testing

Payment gateways are complex systems consisting of both software and hardware components. Software testing focuses on verifying business logic, user interfaces, integration with external systems, and application security. 

Equally important is testing the hardware layer. Servers, storage systems, network components – all these elements must be checked for performance and reliability. Particularly critical are load tests simulating real-world usage conditions during peak traffic periods.

Testing should also include failure scenarios – what happens when one of the servers fails? Can the system automatically switch to backup components? Do data recovery procedures work correctly?

Case Study: A Sale That Turned into a Disaster

We know of a case involving a large e-commerce retail chain that experienced losses during a major sale when the payment gateway system couldn’t withstand increased load. The company was preparing for the biggest sale of the year – marketing was perfectly prepared, warehouses filled with merchandise, customer service team reinforced with additional staff.

However, preparations didn’t include thorough checking of the payment gateway’s technical infrastructure. In particular, no one verified the condition of hardware components that worked without problems under normal load.

When traffic on the site increased multiple times during the sale, and the number of payment transactions reached record levels, the infrastructure couldn’t withstand the operation intensity. Customers couldn’t complete purchases, carts were abandoned, and for several crucial hours, the company effectively couldn’t sell online.

The losses were significant – both in terms of lost revenue and reputation. Most painful was that the entire situation could have been avoided. Appropriate load tests conducted in advance would have revealed system weak points, and the cost of necessary upgrades would have been small compared to the losses incurred.

Why Act Now?

Preparations for the next shopping season – whether Black Friday, Cyber Monday, or holiday periods – should begin now. The earlier you identify potential problems, the more time you’ll have to solve them. What should you consider?

Software quality audit should include code review, unit and integration tests, security analysis, and performance optimization. Experienced QA specialists can find problems that may only manifest under high load.

Load testing is an investment that pays back multiple times. Simulating peak period traffic allows identification of system bottlenecks and preparation of appropriate solutions. It’s better to conduct such tests under controlled conditions than to discover system limitations during actual sales.

Capacity planning helps determine whether current infrastructure is sufficient or requires expansion. Sometimes the problem can be solved through code optimization, other times increasing computing power or network throughput is necessary.

Emergency procedures must be thought through and practiced. What will you do when the main server fails? How quickly can you switch to backup solutions? Do you have a communication plan with customers in case of problems?

Not Testing? You’re Testing Your Customers’ Patience.

In the world of SaaS and e-commerce, there’s no room for delays, errors, and user frustration. A stuck payment? That’s not just a lost transaction, but also a signal: „They can’t be trusted.”

Peak sales periods are not the time for experiments, but for achieving goals. Don’t wait for problems – act proactively and ensure payment systems are reliable. Because if you don’t test your gateway… your customer will do it for you. And that test might cost you much more than you think.

Start your audit today so you can sleep peacefully during Black Friday.

Book a free QA consultation!