API quality has a direct impact on the performance of the entire application. If the API does not work correctly, it can lead to failures in the operation of the web application or service as a whole. For this reason, conducting different types of API testing is necessary, and using modern toolÑ– such as API performance testing tool allows companies to reach a new level of understanding of API functioning. This article is devoted to the features of API testing, types of such testing, as well as errors that can be found during such testing.
What Is API Testing?
API testing is necessary to understand how accurately the API meets the expected functionality, security measures, and performance levels. Specialists can test the API directly or perform integration testing.
API is the code that enables communication and data exchange between two programs. An application usually consists of several layers, including APIs. API layers focus on the business logic of applications, defining requests, how they are performed, and the data formats used.
Unlike user interface (UI) testing, which focuses on checking the appearance of an application, API testing focuses on analyzing the business logic of an application, its security, and the data that the user receives.
API testing is often automated and used by development teams to perform continuous testing. It is usually performed by sending commands directly to the software under test using the application programming interfaces.
How to Approach API Testing?
The API testing process begins with a clear definition of the application scope and a thorough understanding of how the API works. This requires answering the following questions:
- What function does the API perform?
- What endpoints can be tested?
- What response code should be returned for successful requests?
- What is the expected response code for a failed request?
- What is the expected content of the error message?
- What are the expected best solutions for API testing?
- With answers to these and other questions, testers can begin to apply various testing techniques and, if necessary, write code to test the API.
Test cases written for API testing should define conditions or variables that testers can use to verify that a particular system is responding as expected and functioning correctly. The definition of test cases is followed by the execution stage. The goal is to compare the expected results with the actual ones, i.e. to confirm or refute them. Tests analyze responses such as:
- Request response time.
- Data quality.
- Authorization confirmation.
- HTTP status codes.
- Error codes.
Types of API Testing
In order to assess how correctly an API works, different types of testing can be applied. They generally differ in the set of tasks that need to be analyzed.
Validation Tests
This testing analyzes the following aspects: application programming interface performance and usability. Some typical questions asked when performing these tests include:
- Does the API meet the product goals, and does it solve the problems it is supposed to?
- Are there any serious bugs in the code that could break the API?
- Does the API access data according to the stated policy?
- Does the API store data according to security or regulatory guidelines?
- Can any changes to the code improve the overall functionality of the API?
Functional Tests
Functional testing ensures that the API works as expected. As part of testing, specialists evaluate how correctly certain functions in the codebase work. The goal is to make sure that the API can function within the expected parameters and can also handle errors if the expected parameters are exceeded.
Load Testing
Used to determine the number of calls an API can withstand. This type of testing is usually performed after a specific module or codebase has been completed. Specialists try to find out whether a theoretical solution can function in practice under a given load.
Reliability Testing
This type of API testing is necessary to ensure that the API can generate consistent results and that the communication between all components is stable and reliable.
Security Testing
Security testing tests the encryption methods used in the API as well as the access control scheme. It includes checking authorization for access to resources and managing user rights.
Penetration Testing
This testing is focused on security testing. It involves attacking the API by a person with no knowledge of the software. Experts can thus evaluate the attack vector from the attacker’s perspective. Such attacks can be limited to specific elements or target the API as a whole.
Fuzz Testing
In this testing, testers inject a large amount of fuzz into the system to cause certain negative behavior patterns, such as a crash or data overflow.
Unit Testing
During this testing, different modules of the application (units) are tested individually, independently of each other, to ensure that they are working correctly. The process of unit testing an API involves testing individual endpoints with a single request.
Integration Testing
Within this type of testing, specialists test different components of an application as a whole. Thus, this testing is aimed at assessing how the API integrates software, which consists of different interconnected important components.
Common Errors You Can Find When Testing an API
API testing typically reveals the following software errors:
- API reliability issues.
- API response time.
- Duplicate functionality.
- Request limit exceeded.
- Incorrectly structured response data.
- Lack of functionality.
- Multithreading issues.
- Security issues.
- Unused flags.
Conclusion
APIs are now common because they allow businesses to deploy software more efficiently. So, if one part of the application requires an update, others can work independently and without problems. Each component of the product has a separate data store, as well as unique commands for interaction. Most microservices use APIs.As microservices become more common, API testing becomes more important to ensure that all components work correctly, and tools such as the testing API performance are effective here. If you are interested in high-quality API testing services, then you should pay attention to PFLB. The company has over 15 years of experience in load testing and cooperates with companies from various industries.