API testing types

API testing is generally categorized into common categories below:

Validation Testing

Validation testing is among the final steps and plays an essential role in the development process. Validation test helps verify the aspects of product, behavior, and efficiency.

In other words, the validation testing can be seen as an assurance of the correct development against the stated user needs and requirements.

Functional Testing

Functional testing includes the testing of particular functions in the codebase. These features are the representation of specific scenarios to make sure the API functions are handled well within the planned parameters.

End-to-end Testing

UI testing is defined as a test of the user interface for the API and other integral parts. It is mainly about the UI functions, in which the interface is naturally graphical or rely on the command-line endpoint calls.

Generally, the test is more likely of the interface which ties into the API rather than the API testing itself. Although UI testing is not a specific test of API in term of the codebase, this still provides overview information about the health, usability, and efficiency of both front-end and back-end.

Load Testing

Load testing is generally done after a specific unit, or the whole codebase has been completed to check if the theoretical solutions work as the practical plan.

Load testing is performed to ensure the performance under both normal and at peak conditions. To do so, load testing takes on some various scenarios:

Baseline – tests the API against theoretical regular traffic that the API expects in ordinary usage;

Theoretical maximum traffic – this is to make sure during the full load periods, the solutions respond to those requests properly;

Overload test – to test the maximum capability according to the theory, then add 10-20% more on the peak traffic.  

Runtime/Error Detection

This testing type is related to the actual running of the API, particularly with the universal results of utilizing the API codebase. Generally, they focus on one of the below aspects:

Monitoring: The runtime of the compiled code is tested for different implementation errors, handler failures, and other intrinsic issues to help ensure the codebase does not contain any insecurity.

Execution Errors: The code needs to show the response to valid requests and marks the failure for invalid requests predictably and in a known way, just the same with valid requests.

Resource Leaks: The requests which are invalid or commonly illegal will be submitted to the API to test the memory, resource, data, or operation leaks/insecurities

Error Detection: The known failure scenarios will be used to test the code to make sure the errors are appropriately figured and resolved

Security Testing

Security, Penetration and Fuzz testing are the three separate elements of the security auditing process. They are used to ensure the API implementation is secure from external threats.

Besides enclosing with penetration and fuzz testing, security testing also includes additional steps like the validation of encryption methodologies, and of the design of the access control for the API. It also contains the user rights management and validating authorization checks to access the resources.

Penetration Testing

Penetration testing is considered the second test in the process if auditing. In this testing type, the users with limited API knowledge will try to attack to assess the threat vector from an outside perspective, which is about functions, resources, processes, or aim to the entire API and its components.

Fuzz Testing

Fuzz testing is another step in the whole security audit process. In this testing type, a vast amount of random data (referred to as “noise” or “fuzz” ), will be input into the system with the aim to try a forced crash or any negative behavior. This fuzz test will help test the API in term of the limits to prepare for the “worst case scenarios.”