Natalie Monko Lead Project Manager

• Fintech

April 21, 2022 8 min read

How to Perform Payment Gateway API Testing: Best Practices

The digital payment segment is among the most fast-growing markets in the financial sector. Technological advancements stipulated shifts in consumer preferences, from in-store and cash payments to online methods, including cards, electronic wallets, and cryptocurrencies. 

The COVID-19 pandemic significantly contributed to the increased demand for virtual payments. To ensure business continuity, numerous organizations were forced to start delivering goods and services via the Internet only. Customers, in turn, highly enjoyed the possibility to carry out contactless transactions and shop from home, this way staying safe during the outbreak. 

As online payments and money remittances provide convenience and cost savings (people do not have to pay transport costs required to visit a store or bank), their popularity will continue growing even after the end of the coronavirus pandemic. According to Statista, digital transaction value is anticipated to spike by 15.2% in the US, 16.3% in Europe, and 11.2% in China between 2020–2025. Insider Intelligence reports that online money transfers are projected to account for $428 billion, climbing by 45% from 2021 to 2025. 

At the moment, brands and institutions across various industries like fintech, food delivery, e-commerce, and entertainment are integrating payment gateway APIs (application programming interfaces) into software solutions to let customers easily perform orders and money remittances. 

However, to offer a seamless user experience (UX), enable security, and increase reliability, vendors have to provide the proper operation of the transaction verification process. Since any issue, associated, for example, with data safety or performance, has a direct impact on merchant revenue, user trust , and overall traffic volume, it is crucial to perform thorough payment gateway API testing prior to software product release.

In this article, Surf will explain how to test payment gateway functionality and what problems you can avoid due to thorough testing. 

What is QA and why is it important to focus on this stage? 

Quality assurance is a part of the software development life cycle (SDLC) that aims to monitor respective processes and techniques for delivering superior solutions and meeting project requirements. In fact, QA encompasses software testing that focuses on identifying bugs and errors. 

However, QA goes beyond and involves tasks such as achieving performance, security, and compliance with industrial standards. What’s more, QA teams make sure that developers follow best software engineering practices when building a digital product.

In order to carry out payment gateway API testing, QA experts should be aware of its tasks and functions, as well as know respective terminology.

There are several parties involved in the payment process: buyer, merchant, banks, card networks. A gateway acts as an intermediary between merchants and consumers while banks are responsible for ensuring data privacy. Representing a third-party digital terminal, a gateway solution serves for verifying customer identity and authorizing transactions. 

When a user makes a purchase, payment card data is sent to the gateway system. To ensure security, payment gateways encrypt sensitive information, such as user names, passwords, card numbers, and CVV. The gateway transfers this data to the acquiring bank of a merchant and then—to the organization that issued a user card, for instance, Mastercard or American Express. 

The gateways, involving market leaders like Stripe, PayPal, Square, and Braintree, ensure compliance with Payment Card Industry Data Security Standards (PCI DSS) and other regulations. 

Furthermore, gateways protect companies from a variety of issues, covering fraud, expired cards, and exceeding credit limits. To learn more about payment gateways and their most popular providers, read our article on the topic.

To remain competitive, businesses have to enable high availability of their services, so that users can make purchases or money transfers at any time, despite heavy loads and system failures. Operating with highly sensitive data, enterprises must ensure protection against a variety of security threats, from hacker attacks to malware. Additionally, to keep users satisfied, online payments should take a few seconds. With the view to address the above-mentioned challenges, it is essential to conduct payment gateway API testing.

Let’s consider how a QA team carries out payment gateway API testing to prevent potential issues (bugs, errors, security vulnerabilities, unstable performance, and others) and improve user experience, this way raising the conversion rate.

How to perform payment gateway API testing

Payment gateway testing scenarios 

At Surf, we have extensive experience in testing different kinds of software, especially banking and finance apps that use payment gateways to enable money transfers and digital transactions. When testing respective software solutions, QA engineers shall address a wide range of issues to ensure that everything works as intended. 

The first step is collecting the necessary test data. This data comprises dummy card numbers that are generally utilized by merchants around the world (Visa, Amex, Discover, UnionPay, and others). 

Additionally, there is a need to check whether the gateway supports all other declared payment options such as digital wallets (Google Pay, Apple Pay, Samsung Pay), bank directs (like Bancontact, iDeal, Giropay, P24, SOFORT), and cryptocurrencies.

A good practice to test gateway functionality is to utilize the Payment Processor Sandbox, which is a separate testing environment used by QA engineers, to avoid the need to pay real money. 

QAs analyze numerous payment gateway testing scenarios that include among others:

• Checking different combinations of payment details used by customers to make a purchase or money remittance, for instance, “Invalid card number + valid expiry date + valid CVV” and “Valid card number + valid expiry date + invalid CVV”. 

• Ensuring that user funds are withdrawn after a transaction is authorized.

• Verifying that a user receives an email about successful payment.

• Verifying that a consumer gets a notification indicating a reason for payment failure.

• Trying to turn off the Internet when carrying out a transaction.

• Clicking the “Back” button after a transaction is confirmed.

• Trying to provide payment information when a session is not active.

• Changing localization settings during the payment process.

• Checking whether funds are debited from a user card when the gateway system does not respond to requests.

By testing the payment functionality (adding goods to the shopping cart, applying discounts and promo codes, making a purchase, filling out the necessary information), QA experts verify the proper execution of the entire process while providing security and uninterrupted performance.

A payment gateway testing checklist 

In order to verify that a software system performs as intended, quality assurance engineers practice using checklists that contains points such as:

• Every payment method supported by the gateway solution triggers a respective payment flow.

• A user is not able to carry out a transaction while not providing the necessary information.

• The gateway supports currencies indicated in a technical specification.

• The system shows a relevant message to customers if their card data is blocked.

• A transaction is not authorized if a card has expired.

• Payment is not made if there are no sufficient funds on a user account.

• User data is sent to the gateway via a secure channel, for example, HTTPS.

• If the app or website suggests users keep card information to automate transactions, this data is encrypted.

At Surf, we have our own knowledge base that involves test scenarios, checklists, and valuable tips that assist the team in their work. This also allows us to onboard new QA experts much faster. Using best practices and documentation, we are able to quickly train clients’ in-house specialists and transfer testing processes to them if required.

Types of payment gateway API testing

1. Functional testing

The QA team verifies that the gateway successfully resolves user needs and behaves in compliance with project requirements, for instance, supports the necessary payment options and authorizes transactions in a few seconds. At this phase, QA engineers prepare test cases to check the user interface, validation for all data fields, as well as navigation throughout the payment and checkout processes.

2. Security testing 

Since transactions are subject to cyberattacks, it is essential to prevent any risks. For this purpose, QAs conduct security tests by analyzing the system for vulnerabilities to potential threats. 

Payment gateway API testing includes validating that sensitive data is encrypted and transferred via secure channels, and verifying that only authorized users can make payments while automatically receiving warning alerts about suspicious activities.

3. Integration testing

To ensure the proper operation of a software system and its payment functionality, the QA team conducts integration testing. This process is meant to verify each step of the transaction, from clicking the “Add to Cart” button to payment authorization. 

4. Performance testing

When building an app or website, it is crucial to enable its stable, uninterrupted performance, vital to delivering a seamless user experience (UX) and preventing downtime. Otherwise, a business may encounter customer churn due to platform unavailability caused by peak loads, and lose a lot of money.  

Final words

To create top-notch products, you shall thoroughly test the gateway functionality of websites and applications, analyzing all scenarios possible and making sure everything works as designed. By focusing on this stage of custom software development, QAs prevent potential issues associated with:

• Security
• Performance
• User experience

Thanks to high-quality products that align with project requirements, businesses improve customer engagement, minimize bounce rate, and save costs. Furthermore, delivering a seamless UX  significantly increases the credibility of company services.