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What all you need to know about API Testing

by The Post Zilla
API Testing

What all you need to know about API Testing

API Testing describes how one software program communicates and exchanges data with one another software program.


GUI testing mainly takes place on the presentation layer. While API testing is totally different from GUI testing. It generally applies to the business layer of an application. API testing is responsible for checking if API is giving the expected results.  Whether it is reliable, its performance, and whether it is secure or not. However, API testing does not focus on the outward look of the application. It mainly concentrates on API’s performance as well as integration. API Testing Training in Gurgaon can be the best medium to add this expertise as your skill.

Different kinds of API Testing

There are different types of testing on API

Unit testing

Security Testing

UI testing

Interoperability and WS Compliance testing

Functional Testing

Load Testing

The run time or Error Detection

Unit Testing: Unit testing is about the testing of a unit or some specific functionality.

Functional Testing: Functional testing is for testing functions in the codebase. These tests run to ensure API functions are within expected parameters and correctly handling errors.  

Load Testing: Load testing is done to ensure the performance as well as the functionality of an API under load.

Security Testing: Security testing takes place to ensure the API is secure from outside threats.

UI Testing: UI testing is a test of your user interface for API and its essential components. It especially looks after the function of UI, whether the interface depends on command line calls or even it is graphical in nature.

Runtime Error Detection: This test is responsible to identify exceptions or resource leaks to secure future erroneous scenarios.

Penetration Testing: Penetration testing is done to determine how vulnerable the application is to attackers.

Fuzz Testing: Fuzz testing is negative testing to examine how API behaves in a worst-case scenario.

Interoperability and WS Compliance Testing: It only works for SOAP APIs. It usually checks 2 fields. Firstly, you check Interoperability by making sure with Web Services Interoperability Profiles. Secondly, compliance checks make sure standards like WS-Discovery, WS-Addressing, WS-Federation, WS-Security, WS-Policy, and WS-Trust are properly utilized and maintained.

API Test Environment Setup

API Testing falls different from another testing as GUI does not involve API Testing. To test API, you require to set up an environment, which accepts input parameters, invoke APIs with those parameters and derive the result.

To set up the API Test environment, you need to configure the database and server as per application requirements. After its installation, you can call API functions to verify if API is working or not.

Test Cases for API

Below is the list of some usual tests you carry for testing:

Return value for an input condition: You need to verify responses on the basis of the request. It is comparatively easy to test as input variables are known and further it authenticates the results.  

Effect of updating data structure: If we update data structures, it will also affect the outcome of an API. Further, you need to authenticate this outcome.

Redirection of an API – an event or another API call: If an API redirects control to an event or another API then it should also track the rest.  

In case of no return value: When API does not return any value, it must verify its behavior.

Resource Modification: If API calls modify some resources, then it needs to verify and validate those resources accessing them.

API Testing Approach

There are different points that help in choosing the best API approach

  • Start by defining the scope of the program by understanding the functionality of the API program.
  • Set up the test environment which generally includes database and server configuration as per the application needs.
  • Perform testing by using multiple testing techniques like boundary value analysis, equivalence classes, as well error guessing. Also, start writing test cases for the API.
  • Plan and define input parameters for proper implementation of API
  • Perform test cases with known input configurations and also ensure API meets the expected result.


After reading all these points about testing, you must have got an idea about its basic performance. To make the learning process, even more, easier API Testing Online Training in India can be of great help. Thus, start learning and exploring the different opportunities at your hand.

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