Application Programming Interfaces (APIs) enable business applications to interact with each other. Whatever be the platform or technology the applications are built upon, APIs facilitate the exchange of data between them. APIs are playing a leading role in accelerating application integrations and digital transformations. While development of APIs assumes business-critical importance, testing the APIs on time is equally important to ensure product release velocity.
In this article, Sai Dinesh, Software Test Engineer, Qapitol QA introduces the concepts of API testing, provides an insight into the approaches, identifies some best practices and concludes with an example of the risks involved in not performing API testing efficiently.
Before diving deep, we have to make sure that we are prepared with the following three things:
The API documentation helps us understand the business logic and also the importance of the API. This document provides an idea as to what are the different technologies used for the particular SUT (System Under Test).
One should have knowledge of the tool and what features it offers that makes it the perfect tool for testing the API. Choose the tool wisely based on your analysis. (Personally, I recommend Postman).
It is safe to have a separate test environment so the changes/issues don’t affect the QA environment and the teams working on it.
An API stands for Application Programming Interface. An API simply states the set of rules for the communication between systems/services.
The purpose of API Testing is to check the functionality, reliability, performance, and security of application programming interfaces. It mainly concerns with the business logic layer. API testing helps find vulnerabilities that may be missed in functional testing (UI level).
An API testing approach is a predefined strategy or a method that the QA team will perform. This helps to better understand the functionalities, testing techniques, input parameters, and the execution of test cases and also will help testers with better coverage.
The following points will help the tester to design the API testing approach:
API testing helps in better understanding of the core logic of an application and its functionalities. Each test consists of test actions. These are the individual actions a test needs to follow as per the API test flow.
For each API request, the test would need to perform the following actions:
API testing should cover at least the following testing techniques:
Functional testing: This testing involves validating the functionality of an API according to the business logic.
Validating the Request/Response with various inputs: This includes productivity, behavior, and the efficiency of an API, while validating the user inputs and handling the exceptions and limiting the request payload size.
Usability testing: Verifying whether an API affiliate works well with another platform as well and check if error logging is happening or not. (For shared APIs)
Security testing: This testing includes what type of authentication is required and whether sensitive data is encrypted over HTTP(s). Understanding what level of encryption is performed may also be a part of this and includes Pentesting & Fuzz testing.
Performance testing: API performance will have a major impact on the application responsiveness. So testers have to make sure that the average response time for an API must be within designed limits under various circumstances.
API design test: As a part of the design test, one should validate whether the APIs have been developed with the REST principles or not.
Maintaining a checklist is one of the most important practices as it helps to be on track and also to determine additional test cases for good coverage. Here is a checklist for some of the most important testing techniques mentioned above.
HTTP headers play a key role in the API world. Headers guide the application & server to understand the Request and Response. Headers also help to prevent hacking.
Headers are mostly classified into two types — Response and Request headers.
As a part of Header validation, we have to analyze how an API behaves with/without Headers and by manipulating the values of the Headers. when sending the request for testing an API, will have to set the Assertion against the response Headers to ensure that the right Headers are being returned.
Here is the sneak-peak of some of the secure Headers that help to prevent the APIs from the major cyber-attacks.
As discussed earlier securing an API is the most critical and important aspect of testing.
Of all the components that make up an application, APIs provide the easiest access point for a hacker.
Here is the checklist for the API security testing:
There is always room for improvement.
Here are some of the best practices that we can follow to improve our skills in API testing for better coverage.
A very popular company that provides local search for different services over the phone and online redesigned its apps, but left the outdated APIs running and unprotected with access to the user databases. When this event got exposed, the company had to face a loss of reputation and experienced a dent in its business.
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