What Is API Testing?

Applications are typically made up of a data layer, a service layer, and a presentation layer. The service layer describes how users can interact with the app’s services, data, and functions. Since the service layer interacts directly with both the data layer and the presentation layer, it is an important piece of the application security puzzle.

The process of testing APIs usually involves making requests to API endpoints and validating their responses. Since APIs enable applications to interact with one another automatically, careful testing is vital to ensuring security flaws and vulnerabilities are not exposed.

What Does API Testing Achieve?

Testing reduces risk and makes applications more reliable. The cost of exposing a bad or poorly secured API to the internet is much higher than the price of testing.

For this reason, API testing is a requirement of many compliance frameworks, including PCI-DSS, HIPAA, and ISO 27001. These frameworks require organizations to secure the storage, processing, and transmission of sensitive data—including data transmitted through an API.

Organizations that commit to regular API testing also gain important benefits:

• Improved quality assurance. API errors and security issues can erode customer trust and harm your organization’s reputation. Continuous testing allows you to find and address these problems before users do.
• Early detection of security issues. Threat actors consider APIs high-value targets because they often provide deep, automated functionality with little oversight or visibility. Comprehensive testing ensures you patch security vulnerabilities before threat actors can exploit them.
• Verified authentication and authorization. APIs do not always leverage the same authentication and authorization methods that other network assets use. This exposes them to security weaknesses that can only be discovered through extensive testing.
• Efficient use of system resources. The more resources your APIs use, the less efficient your overall network environment becomes. API testing can help identify opportunities to improve the efficiency of automated operations.
• Faster CI/CD iteration. Many organizations deploy APIs in a DevOps model, enabling continuous integration and continuous deployment (CI/CD). Automated API testing ensures the team can rapidly validate code changes, preventing bottlenecks in the CI/CD pipeline.
  

How Does API Testing Work?

The process of testing APIs involves creating a testing environment with a specific set of parameters around the API. To do this, testers must configure the database and server to meet the application’s requirements. They must also review the API specification and understand what to expect when sending requests to it.

After that, testers will define input parameters that should result in the API taking specific actions. These parameters depend on the type of API being tested—for example, RESTful APIs accept header, query, and rest body parameters.

Testers will plan out a comprehensive list of input combinations and observe how the API responds to them. Professional testers use a combination of positive and negative tests to do this.

• Positive API tests verify the functionality of the API using valid user input and parameters. This ensures the outcome of valid requests meets user expectations.
• Negative API tests verify how the API responds to invalid user input and prohibited operations. This provides visibility into how secure the API is against many types of cyberattack.

API testers use a variety of tools to conduct these tasks. Postman is one of the most popular options on the market, alongside SoapUI and JUnit. Many of these options provide enhanced features for automating API testing and ensuring continuous performance monitoring and improvement.

What Kinds of Threats Does API Testing Defend Against?

API security risks include some highly technical attack tactics often carried out by sophisticated threat actors. Some of the threats that API testing can help identify and address include:

• Broken Object Level Authorization (BOLA): This exploit occurs when attackers manipulate the ID of objects sent in requests.
• Inadequate authentication: If the API does not authenticate users before accepting their input requests, it may allow attackers to send malicious requests.
• Excessive data exposure: This happens when API responses reveal more data than is strictly necessary. 
• Insufficient rate limiting: Rate limiting helps prevent Denial-of-Service (DOS) attacks and ensures smooth API operation.
• Injection attacks: This is when attackers send malicious data to the API and trick it into executing malicious commands.
• Insufficient logging and monitoring: API interactions should generate comprehensive logs that feed into a Security Information and Event Management (SIEM) platform.
• Insecure Direct Object References (IDOR): This happens when threat actors abuse API tools by manipulating input values.
• Misconfigured CORS: API misconfigurations can allow unauthorized domains to access your network. 
• Known vulnerabilities in API components. Your API may rely on libraries and other components that have recently discovered vulnerabilities. These must be patched to ensure a secure workflow.

What Are the Different Types of API Testing Methods?

There are many different types of API testing methods. Each one is designed to verify the functionality of a particular component or use case in the API:

1. Unit testing involves verifying small, isolated parts of the API to ensure good functionality. Testing how the API authenticates user logins is an example of unit testing.
2. Functional testing makes sure the API functions as expected. That usually means simulating user inputs and verifying the results.
3. Performance testing ensures the API operates as efficiently and reliably as possible. For example, you may test the API’s speed and responsiveness under peak usage.
4. Security testing looks specifically for security misconfigurations and vulnerabilities that attackers may exploit.
5. Penetration testing goes one step further than security testing, simulating attacks using real-world techniques to show what the likely consequence might be.
6. Integration testing verifies the API’s handling of third-party integration features. In a PCI-DSS compliance environment, that might mean testing the API’s payment gateway integration.
7. Load testing specifically focuses on how the API responds to high user traffic scenarios. 
8. Stress testing specifically looks at how the API responds to sudden spikes in user requests, or large data requests.
9. Fuzz testing sends random inputs to APIs, looking for unexpected errors and other unforeseen risks.

API Test Automation Enables Continuous Validation

API testing is an important part of web application security, and a key compliance requirement for many organizations. It can also be a time-consuming and painstaking manual process. Automating API testing enables organizations to meet compliance requirements and ensure API security without drawing talent from other high-impact tasks.

Novawatch can help you conduct comprehensive API testing and ensure your organization’s applications are securely connected to one another and to the public internet. Reach out to an API testing specialist to find out how we can help.