Application programming interfaces (APIs) are some of the most important concepts in modern software development. RESTful API is considered the most popular and flexible, and it’s becoming more widespread.
However, they must be properly maintained and tested to minimize the chances of unwanted outcomes, such as malfunctions and cybersecurity risks.
This article breaks down the concept of REST API testing and some of the best practices that will help developers and QA specialists in the development process.
What is REST API testing?
REST ( or Representational State Transfer) APIs use HTTP protocols for communication, making them widely used for connecting web and mobile applications to servers or external services. For example, REST APIs can help manage user data through CRUD.
REST API testing aims to evaluate its functionalities, reliability, and security, and confirm whether it’s working as intended.
Here are a few problems that REST API testing aims to recognize:
- Mishandles requests and responses: Returns wrong data, error codes, and messages.
- Processes data inaccurately: Data isn’t stored and retrieved correctly.
- Unreliable under specific loads: Becomes inaccessible when under large data volumes and when handling multiple users.
- Vulnerable to cyber threats: Can be potentially exploited through brute force attacks.
You can use several methods to leverage each of these potential problems. API testing tools, such as Apidog, can streamline the process.
5 Best methods for REST API testing
REST API testing ensures that there aren’t any error codes that could compromise your application.
With these five testing methods, you’ll undoubtedly minimize the chances of such problems, but nothing can guarantee a bug-free code. You should always consult experts in your niche and leverage the most applicable methods to your specific case.
1. Test CRUD Operations Thoroughly
CRUD, Create, Read, Update, and Delete operations are the foundation of REST APIs, enabling data manipulation. Testing these operations ensures the API works as intended in all scenarios.
The key steps of testing CRUD include:
- Create (POST): Test resource creation with valid and invalid payloads. Check that the database reflects changes.
- Read (GET): Check data retrieval for specific resources or collections.
- Update (PUT/PATCH): Ensure all updates are applied correctly and that partial updates work if using PATCH.
- Delete (DELETE): Remove resources. – You cannot access these afterward.
You should streamline this process using automated tools to test CRUD operations across multiple environments. For example, an app you’ve made works on a PC but has problems on Android. Testing it on different devices allows you to recognize what the problem is.
2. Validate HTTP Status Codes
Even if you’re a regular internet user and not a developer, you’ve probably come across the “404 Not Found” HTTP status code.
HTTP status codes indicate whether the server has completed the required request.
It is important to test these to ensure that the clients receive proper HTTP status codes.
You should mainly test the most common codes:
- 2xx: This refers to a successful message. This means that the server has successfully received and accepted the client request. Examples include “200 OK” and “201 Created”.
- 4xx: This refers to an error message. It means that the page is unavailable or that the website (or page) could not be reached. Examples include “404” and “400 Bad Request Error.”
There are 5xx status codes that occur because of internal problems, which you should also test. These include, for example, “500 Internal Server Error” and “502 Bad Gateway”.
It’s also best to include test cases for rare and specific scenarios, such as malformed requests or expired tokens. Then, verify how the API responds to rate limits or timeouts.
3. Use secure coding
One of the most important types of tests for REST APIs occurs early in the development process. Secure code scanning is a powerful practice that helps conduct security testing during development and finds vulnerabilities.
Later, these vulnerabilities can cause larger problems, such as delaying development and causing financial losses.
This proactive approach strengthens the security of your APIs and saves time and effort by addressing problems during the development phase. Incorporating secure code scanning as part of your API testing best practices ensures that your APIs are robust, reliable, and protected against evolving threats. It’s a must-have step for any team aiming to deliver secure APIs.
4. Test Input Validation
Input validation is a test that safeguards against malicious data and ensures the API processes requests correctly. Its most important feature is testing for proper data formatting and length.
It helps you validate all the input fields, such as headers and query parameters. This type of test can also check for potential vulnerabilities, like SQL injection and cross-site scripting (XSS).
5. Perform Load and Performance Testing
Conduct load and performance testing to ensure that your application works under high traffic. This is essential for proving reliability and scalability for future development ideas.
This test occurs through API testing tools that simulate concurrent requests, often in an event-driven architecture where systems respond to events such as high traffic or API calls. These also allow you to test under different network conditions (e.g., high latency, low bandwidth) to measure performance.
You should evaluate response times, error rates, and throughput during these tests.
Pick essential practices for REST API testing
Testing REST APIs is becoming a non-negotiable requirement for delivering high-quality, secure, and reliable products.
There are other API tests that check that your code works well. However, we’ve outlined the five most common practices that improve the functionality and security of your API and enhance the overall user experience.
In the long run, this can improve customer engagement and retention and help you gain a competitive edge in your industry.
