A payment gateway is an e-commerce service that processes, verifies and accepts credit and debit card payments for businesses. The global payment gateway market is projected to increase from US$26 billion in 2022 to US$189 billion by 2032. Payment gateway testing verifies the functionality and security of a payment gateway to ensure that the system can process online transactions accurately and securely.

Below, we'll cover what businesses need to know about types of payment gateway testing, how each type works and why keeping up with this testing is important.

What's in this article?

• Types of payment gateways
  
• Testing types for the payment domain
  
• Payment gateway testing scenarios and use cases
  
• Sample payment gateway test
  
• Why testing payment gateways is important
  
• A checklist for preparing test cases for a payment gateway
  
• How to test a payment gateway: A checklist
  

Types of payment gateways

Each type of payment gateway has advantages and considerations to take into account when it comes to integration complexity, user experience and security requirements.

• Hosted payment gateways: These gateways redirect the customer to the payment service provider's platform to complete the transaction. Once the customer has completed the payment, they are then redirected to the business's website. This method benefits businesses because it outsources most of the security requirements to the payment service provider. Examples of hosted payment gateways include PayPal and Stripe.

• Self-hosted payment gateways: These gateways collect payment details from the customer within the business's website or application before sending the data to the payment gateway's URL. Some gateways require the business to capture the payment data in a specific format, while others offer more flexibility. This method puts greater security obligations on the business because it needs to handle and secure the payment data.

• API-hosted payment gateways: These gateways let businesses integrate payment processing capabilities into their websites or mobile applications using the gateway's application programming interface (API). API-hosted payment gateways provide a better user experience because customers do not need to leave the business's platform to complete the transaction, as required with hosted gateways. Note that this type of payment gateway has the same security obligations as self-hosted payment gateways.

• Local bank integration gateways: This type of gateway redirects the customer to the website of their chosen bank to complete the payment. Once the transaction has been processed, the customer is redirected to the business's site, where the payment status is displayed. This method is straightforward but may not provide the best user experience because the customer has to leave the business's site to complete the payment.

Testing types for the payment domain

Testing payment gateways ensures that payment processing systems are reliable, secure and efficient. Here are several key testing types that are relevant in the payment domain:

• Functional testing: This type of testing checks that the payment system operates according to its specified requirements, by verifying payment processing, transaction statuses, refunds, chargebacks and reconciliation processes.

• Security testing: This type of testing checks for vulnerabilities to threats, such as structured query language (SQL) injection and cross-site scripting (XSS), as well as for compliance with security standards, such as the Payment Card Industry Data Security Standard (PCI DSS). It also scrutinises encryption mechanisms and data protection measures.

• Integration testing: This type of testing checks whether the system can be integrated successfully with various systems, such as e-commerce platforms, banks and fraud detection systems, and then exchange data accurately.

• User interface testing: This testing checks whether the payment gateway is user-friendly and intuitive, with clear instructions and feedback, to reduce the likelihood of errors and abandoned transactions.

• Performance testing: This testing checks whether payment systems can handle high volumes of transactions, especially during peak periods.

• Compatibility testing: This testing checks whether the payment system can provide a consistent user experience by working across different platforms, operating systems, browsers and devices.

• Regression testing: Whenever updates or changes are made to the payment system, regression testing checks that these changes don't have an adverse effect on existing features.

• Compliance testing: This testing verifies adherence to legal and regulatory standards, such as the PCI DSS for payment card data security.

• Disaster recovery and failover testing: This testing evaluates the system's ability to recover from failures and continue operating.

Payment gateway testing scenarios and use cases

Payment gateway testing involves running these systems through a series of scenarios and use cases to check whether they're functioning as desired. Common testing scenarios and use cases are outlined below.

Transaction processing

• Successful transaction: Verify that payments can be processed successfully using valid payment details. Check whether the transaction status has been updated correctly and whether the funds were transferred as expected.

• Failed transaction: Test with invalid card details or insufficient funds to check whether the transaction fails as expected and that the user receives a clear error message.

• Pending transaction: Some transactions may not be processed instantly and could be marked as pending. Verify that pending transactions are handled correctly and updated once they have been processed.

Card information

• Card validity: Test with expired, invalid or blocked cards to check whether the system validates card details properly.

• Save card information: If the gateway allows users to save their card details for future transactions, test the save functionality to confirm that the data has been stored securely and retrieved correctly for subsequent transactions.

Security and compliance

• Encryption and data protection: Check whether sensitive information, such as credit card numbers and card verification values (CVVs), is encrypted properly during transmission and storage.

• PCI DSS compliance: Verify that the payment gateway complies with all PCI DSS requirements.

User interface and experience

• Input validation: Test all input fields for proper validation, including card numbers, expiry dates and CVV codes. Confirm that users are receiving appropriate feedback for invalid inputs.

• Responsive design: Check that the payment gateway's interface is responsive and works across various devices and screen sizes.

• Localisation: If the gateway supports multiple languages or currencies, test these features to confirm that they work correctly and are user-friendly.

Integration testing

• API integration: Verify that the payment gateway's API has been integrated correctly with the business's system.

• Third-party integrations: If the gateway is integrated with other services (such as delivery, tax calculation or fraud detection), test these integrations for correct functionality.

Error handling and messaging

• Connection issues: Simulate network or server issues to test how the gateway handles connection failures, checking that users receive clear and appropriate messages.

• Timeouts: Test how the system handles timeouts at both the front end (user interface) and back end (server or API level).

Refunds and chargebacks

• Initiate refunds: Test the process of initiating a refund through the gateway and verify that the transaction can be reversed correctly.

• Chargeback process: Test the workflow for handling chargebacks, confirming that the business can respond to and manage chargeback disputes.

Reporting and reconciliation

• Transaction reports: Test the generation and accuracy of transaction reports, confirming that all transaction types (successful, failed and pending) are logged and reported correctly.

• Reconciliation: Verify that the payment gateway's records align with the business's records and bank statements, and that all transactions are accounted for accurately.

By testing these scenarios thoroughly, businesses can ensure that their payment gateway is secure, effective and user-friendly.

Sample payment gateway test

Below is a test case example for verifying a successful credit card transaction through a payment gateway. By walking through each step, you can evaluate how well the payment gateway handles the transaction and gain insights into the user experience and system reliability. The goal of this particular test case is to simulate a real-world scenario in which a customer uses a credit card to make a purchase through an online platform.

• Objective: The main goal is to check whether the payment gateway processes the credit card information correctly, and communicates the transaction outcome to both the user and the business's system. This involves validating the front-end interaction (what the user sees) and the back-end process (how the system handles the transaction data).

• Preconditions: Before you begin, you need a setup in which everything is in place for a transaction to occur, including a test environment that mimics the live payment processing scenario without actual financial implications, and access to a valid credit card for testing (usually provided by the payment gateway for testing purposes).

• Expected results: You're looking for a straightforward process in which the user inputs their details, submits them and receives a clear, positive confirmation that their payment was successful. Behind the scenes, the transaction should be logged correctly in the business's system, reflecting the successful transfer of funds.

Test steps

• Initiating the transaction: Check whether the process of selecting the payment method (credit card) is accessible and functional.

• Entering payment details: Check whether the payment details form is intuitive and guides the user correctly through entering their information.

• Submitting the payment: Check the responsiveness of the system and its ability to send data to the payment processor.

• Observing the outcome: Check whether the transaction was successful from the user's perspective, and assess the clarity and appropriateness of the messages displayed to the user.

• Post-conditions: After the test, check the credit card account and the business's records to verify that the transaction was processed correctly.

• Logging results and comments: Record what happened when the test was executed. Did everything go as expected or were there issues? Note any additional observations, thoughts or anomalies that you encountered during the test to guide future testing and development. This documentation will inform follow-up actions and troubleshooting.

Why testing payment gateways is important

E-commerce and online businesses rely on functional, easy-to-use payment gateways to create a reliable and secure payment experience. Testing the payment gateway can help to fine-tune the payment process in the following ways.

• Anticipating user behaviour: Testing helps businesses understand how customers interact with their payment systems in real scenarios. These insights can drive improvements in the payment process, potentially increasing conversion rates. For instance, seeing where users hesitate or drop off in the process can inform design changes that simplify the payment experience, encouraging a greater number of completed transactions.

• Proactive problem-solving: Testing anticipates challenges by examining the payment gateway under a variety of conditions. Businesses can identify potential points of failure before they affect customers and develop appropriate contingency plans, which ensures that business operations can continue smoothly even under unforeseen circumstances.

• Optimising transaction flow: Testing can reveal insights into the transaction flow's efficiency, such as the time required for different payment methods. This can highlight opportunities for optimisation, potentially leading to faster checkout experiences and greater customer satisfaction.

• Data-driven decision-making: Testing generates a wealth of data, offering businesses granular insights into the payment process. This data can inform key decisions, such as which payment methods to prioritise or where to allocate resources for upgrading the payment infrastructure.

• Strengthening security posture: Security testing can provide businesses with deeper insights into a system's resilience against emerging threats, informing a more calculated approach to security.

• Benchmarking and continuous improvement: Testing allows businesses to benchmark their payment system's performance against industry standards and competitors. This can be a powerful driver for improvement, pushing businesses to update their payment gateway processes on a continuous basis.

• Assessing scalability: Testing can help businesses to assess the scalability of their payment systems, predicting how the gateway will perform as transaction volumes increase or as the business expands into new markets with different currencies or payment methods.

A checklist while preparing test cases for a payment gateway

Here's a checklist to guide you through preparing test cases for a payment gateway. This checklist provides assistance with preparing comprehensive and effective test cases for payment gateway testing, in turn addressing a variety of important aspects to maintain the system's reliability, security and performance.

Pre-test information gathering

Before testing, note the following factors affecting your payment flow:

• Payment gateway integration requirements
  
• Supported payment methods
  
• Expected transaction flow for each payment method
  
• Specific business rules or logic applied during the payment process
  

Test environment setup

• Establish a secure and isolated test environment that mirrors the production setup as closely as possible. Confirm that test payment methods (e.g. test credit card numbers) are ready and operational.
  

Test data preparation

• Prepare valid and invalid test data for various test scenarios, including test data for different payment methods, currencies and countries, if applicable, as well as test data to cover edge cases and boundary conditions.
  

Design test cases

Design test cases across different types of testing that address a range of potential scenarios and check a range of functionalities. Here are the key areas to focus on:

• Functional testing
  
• Security testing
  
• Integration testing
  
• User interface and experience testing
  
• Performance testing
  
• Compliance and reporting testing
  
• Error handling and recovery testing
  

Make sure that all test cases are documented and align with security and compliance requirements. Review and update the test cases as necessary to align with any changes in requirements.

How to test a payment gateway: A checklist

To conduct a comprehensive and detailed assessment of a payment gateway, follow a structured checklist that addresses all key components of the system, such as functionality, security, usability and integration capabilities.

Functional testing

• Confirm that the gateway processes transactions accurately, using all supported payment methods.
  
• Execute tests for successful transactions to verify that funds are transferred correctly and that receipts are generated.
  
• Simulate transaction failures using invalid card details or insufficient funds to evaluate error handling and user notification clarity.
  
• Check how the gateway manages pending transactions and monitors their resolution status.
  
• Test the functionality for processing refunds, cancellations and chargebacks, observing the system's handling and recordkeeping capabilities.
  
• Determine the gateway's ability to handle partial payments or split transactions, if applicable.
  

Security testing

• Conduct compliance checks with security standards, such as the PCI DSS to validate adherence to industry requirements.
  
• Evaluate the encryption mechanisms for sensitive data during transmission and while stored.
  
• Perform comprehensive vulnerability assessments and penetration tests to find potential security issues.
  
• Test input validation for all fields to prevent common web threats, such as SQL injection and XSS.
  
• Examine the mechanisms for user authentication and data access authorisation within the payment system.
  

Integration testing

• Verify transaction flow integration with the website or application's front end.
  
• Test how well the payment gateway communicates with external systems, such as accounting, inventory or customer relationship management (CRM) software.
  
• Confirm that the gateway provides accurate notifications or callbacks after transaction completion.
  

User experience testing

• Evaluate the payment process on a variety of devices and browsers for consistency and responsiveness.
  
• Examine the clarity and helpfulness of payment instructions, error messages and confirmation notifications.
  
• Determine the navigational ease and intuitiveness of the payment process from start to finish.
  

Performance testing

• Analyse the gateway's capability to manage high transaction volumes simultaneously.
  
• Measure the response times under various load scenarios to identify any delays or bottlenecks.
  
• Test the system's resilience and behaviour under stress to pinpoint potential performance issues.
  

Compliance and reporting

• Check that the gateway generates accurate, detailed transaction reports.
  
• Review the system's logging and audit trails to confirm that they are comprehensive and secure for compliance purposes.
  

Error handling and recovery

• Test the system's response to network interruptions, system crashes and other anomalies to verify transaction data integrity.
  
• Validate procedures for managing interrupted transactions or system recoveries to maintain data consistency and operational continuity.
  

Documentation and support

• Review the payment gateway's documentation for clarity, completeness and accuracy.
  
• Evaluate the effectiveness of the gateway vendor's support channels, including help desks, FAQ and customer service responsiveness.