API Testing: What, How & Why?

API Testing: What, How & Why?

API Testing: What, How & Why?

Testing is one of the most vital phases for the development of any product or software and has been practiced in order to deliver better solutions. But every product might demand a different type of testing, for example, though functionality testing does the job for a website, security testing is still required to be done. With major developments in Software Development Life Cycle approaches, we have various types of testing that assure the best quality products through all endpoints and API testing is one such type.

Multiple reasons like Security, Quality, cost-effectiveness, fulfillment of customer’s requirement, understanding the performance, hitting a rock with unknown feature along with how testing helps in enhancing the while development process makes the testing key phase. 

What is API Testing?

A type of testing that involves point testing of Application Programming Interface and is responsible for regulating the requirements for multiple functions in software. Here, we don’t provide any user input but rather a set of calls hit the API and receive the response. Now, to simply explain to you what API is, it is a set of programming commands and tools that programmers can use to write code on multiple levels. Every time we do a simple product search on Amazon, we use APIs written by the developers.

So, API testing is to examine these APIs and improve them. Functions like Performance, Security, Reliability, etc are properly tested. While most of the other testings consist of examining through User Interface, API testing is done on a different level where the design of the product is of no relevance and core business logic is inspected and improved. 

What are the Advantages of API Testing?

Testing is one of the most crucial parts of the development and ensures that the best quality is delivered to the end-user. As per the analysis of Web API Testing Company, Here is the list of different advantages of API testing

  • A number of tests are planned and executed, but this could be a final step to test the main core of the software. 
  • API testing unlike other testings does the job on the code level and minor errors can be eliminated before they turn into major problems in the future.
  • End to End testing of functions is carried out under API testing while Unit testing focuses on separate modules. API testing here has a wider scope.
  • Monitoring the application under various scenarios, which helps developers understand what could possibly go wrong and amend it.
  • Browser Compatibility is achieved through working out multiple scenarios on multiple web browsers.    

How Does an API Testing Work?

Now that we’ve learned what API testing is and how important is it, let us look into how it is done. Basically, API testing is planned after builds are ready and it is crucial you understand the functions of the API that you intend to test. A suitable test environment is established in accord with parameters, and databases and servers are made ready for proper tests.

Multiple questions are asked and answered as a process to have a strong argument through API testings, questions like Target Consumer for API, how the API works normally, Problems that might appear, what will decide the outcome of the test, etc. 

There is a number of tests that fall under API and testing these aspects assure the working of API. Tests like Functionality, Reliability, Load, Security, Proficiency, etc cover most parts of the software on the ground of API testing. One of the most interesting tests is Negative Testing, which is to predict what possibly could go wrong, set up a test, and make sure that even if it goes wrong as predicted, it won’t impact the functionality of the whole.  

Environment: Setting up the environment for testing can be complex as it does not involve any GUI, and all you do is play with parameters hit the database, and invoke APIs.

Test Cases: Multiple test cases are written like what would be the return value, what if there is no response or a null one, what if another API is triggered – whether relevant or not, etc.

Output: With different test cases, different out will be expected, and later it is important to compare the actual output with the expected output. 

Moving on, the errors that can be successfully detected in testing are security and performance issues, handling of unlike conditions, end-to-end working of a single functionality, structure of Response Data, ignored or absent functionalities, etc. These results assist in improving the API for further builds.

Learn Also: What are the Types of API Testing?

Why API Testing is Needed?

Basically, a simple reason for why API automation is required is to make sure the final product is of the best version, ensuring the API implemented functions as intended in multiple factors like security, performance, etc. Every software has a single-core API, so it is essential to make sure it’s working. APIs now being one of the key parts of an application, serving the business logic, makes API testing vital. On the other hand, most tests involve testing the GUI parts and do not bother with the functioning logic of the software.

One of the major aspects of API Testing is to test the capability of the API to perform under pressure. Here, what we refer to as Load Testing is somewhat similar to performance testing, where you have a number of test scripts, test cases, and multiple operations or functions performed, hitting the APIs and receiving response. Every hit to API and its response is recorded, along with time consumed, and performance is evaluated.

Furthermore, testing can be done in two ways like most other tests, which are Manual Testing and Automated Testing. Recent Developments in software enable you to set up a tool for automated testing, while on the contradict manual testing requires you to write test scripts and follow up on each step.


API automation testing is to make sure that the application functions the way it is made to, assurance of every function working properly. It certifies the product of its handling capabilities, security features, and compatibility across platforms. 

Postman, REST Assured, and Karate API Testing is the new trend!

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