Api Testing

API Testing Tutorial: What is API Test Automation? How to Test

The acronym API stands for “Application Programming Interface,” and it refers to a computing interface that makes it possible for two separate software systems to communicate with one another and share data. A software system that executes an API typically contains a number of functions and subroutines that can be carried out by another software system. The Application Programming Interface (API) defines the kinds of requests that can be made between two software systems, as well as how those requests can be made and the data formats that can be used.

Testing of what exactly is an API?

Validating Application Programming Interfaces is the focus of the software testing method known as API Testing (APIs). The purpose of application programming interface testing (API Testing) is to test the programming interfaces for their functionality, reliability, performance, and security. When performing API testing, rather than using standard user inputs and outputs (such as a keyboard), you will use software to send calls to the API, obtain output, and record the response of the system. The Application Programming Interface (API) tests are very different from the Graphical User Interface (GUI) tests and will not concentrate on the look and feel of an application. The business logic layer of the software architecture is where the majority of its attention is focused.

API Testing image

API automation In order to test something, you need an application that has an API you can interact with. You will need to in order to put an API through its paces.

  • Make use of the Testing Tool to control the API.
  • You will need to write your own code in order to test the API.
  • In this tutorial on testing APIs, you will learn more about the following topics:
  • Establishment of an Environment for Testing APIs
  • Variations of an API’s Output Types
  • Case Studies for the Testing of APIs
  • Methodology Used in Testing APIs

Testing of application programming interfaces as opposed to unit testing

How to Perform API Tests

The Most Effective Methods for Testing APIs

API Testing may uncover the following types of errors:

Automating API Tests: A Step-by-Step Guide

The Difficulties in Testing APIs

Establishment of an Environment for Testing APIs

API Testing is distinct from other types of software testing because there is no graphical user interface (GUI) available. Despite this, you are required to set up an initial environment that invokes the API with the necessary set of parameters, and you must then check the result of the test.

As a result, the establishment of a testing environment for API automation testing appears to be somewhat difficult.

  • The database and the server should be configured so that they meet the requirements of the application.
  • Once the installation is done, the API Function should be called to check whether that API is working.
  • Variations of an API’s Output Types
  • One possible outcome of using an API is.
  • Any kind of information
  • Status (say Pass or Fail)
  • Make a call to a different API function.
  • In this tutorial on API testing, let’s take a look at an example of each of the Types mentioned above.

Any Kind of Information

For illustration purposes, there is a function available in the API that should add two integer numbers.

Long add (int a, int b)

The numbers themselves must be provided as one of the input parameters. The output should be the sum of two numbers that are both integers. This output needs to be checked against what was anticipated to happen next.

There is a need to make calls, such as to:

add (1234, 5656)

In the event that the number is greater than the integer limit, handling exceptions is required.

Status (say Pass or Fail)

Take a look at the following API function:




As an output, they provide any value, such as True (in the event that the operation was successful) or false (in the event that an error occurred).

A more accurate description of a test case would say that it is possible to call functions in any of the scripts and then later check for changes in either the database or the application’s graphical user interface.

Invocation of a different API or Event.

The image of the Testing API Approach

In this particular scenario, we invoke one of the API functions, which then causes another function to be invoked.

For instance, the first API function can be called to delete a particular record from the table, and then the second API function can be called to REFRESH the database.

Case Studies for the Testing of APIs:

The testing of APIs is done using test cases based on.

Return value that is dependent on the input condition; it is relatively simple to test because the input can be defined and the results can be verified.

does not give anything in return: A behaviour of the API on the system that needs to be checked when there is no return value

Trigger another API, event, or interrupt: If the output of an API triggers some event or interrupt, then the listeners for that event or interrupt need to be tracked.

The data structure should be updated. Changing the data structure will have some result or effect on the system, and that should be verified.

Modify specific resources: If an API call modifies any resources, then it needs to be validated by accessing the resources that are being modified.

Approach to Testing with the API

After the build is complete, the QA team will execute the predefined strategy or method known as the API Testing Approach in order to perform the API testing. This will occur after the build has been completed. The testing in question does not encompass the source code. The application programming interface (API) testing strategy contributes to a better understanding of the functionalities, testing techniques, input parameters, and the execution of test cases.

The user will find the following points helpful when doing API Testing approach:

Learn testing of APIs in just ten minutes!!!

Gaining an understanding of the API program’s functionality and elucidating the program’s scope both are necessary steps.

Implement various testing strategies, such as error guessing, boundary value analysis, and equivalence classes, and then write test cases for the application programming interface (API).

It is necessary to plan and define the input parameters for the API in an appropriate manner.

Carry out the test cases and examine the differences between the expected and actual results.
How to Perform API Tests

In addition to the typical steps of the SDLC process, API automation testing should cover at least the following testing methods.

Discovery testing requires the test group to manually carry out the set of calls outlined in the application programming interface (API). For example, the group should check that a particular resource made available by the API can be listed, created, and deleted as required.

Testing for usability: This testing determines whether or not the application programming interface (API) is user-friendly and functional. Furthermore, how well does the API integrate with the other platforms?

Testing for security: This testing includes determining what kind of authentication is required and determining whether or not sensitive data is encrypted over HTTP or both.

API testing should culminate in the creation of a set of scripts or a tool that can be used to execute the API on a regular basis. This is what is known as automated testing.

Documentation: The testing team has the responsibility of ensuring that the documentation is sufficient and offers sufficient information to allow for interaction with the API. The final deliverable ought to include documentation as one of its components.

Testing an API using the Most Effective Methods:

It is important to organise API Test Cases according to Test Category.

You need to make sure that the declarations of the APIs that are being called are included at the very top of each test.

The selection of parameters ought to be spelled out very specifically within the actual test case.

Calls to API functions should be prioritised so that testing can be done quickly and easily.

Each test case ought to be as self-contained and free of dependencies on other cases as is practically possible.

When developing, you should try to avoid “test chaining.”

When dealing with one-time call functions such as Delete, CloseWindow, and so on, extra caution and attention are required.

Difference between API testing and Unit testing

Unit testing API testing
  • Developers perform it
  • Testers perform it
  • Separate functionality is tested
  • End to end functionality is tested
  • A developer can access the source code
  • Testers cannot access the source code
  • UI testing is also involved
  • Only API functions are tested
  • Only basic functionalities are tested
  • All functional issues are tested
  • Limited in scope
  • Broader in scope
  • Usually ran before check-in
  • Ran after build is created

The call sequencing process needs to be carried out and carefully planned.

Create API test cases for each of the possible input combinations of the API so that you can make sure your tests cover everything.

API testing can uncover a variety of different types of errors.

Does not gracefully handle the presence of error conditions.

Flags that aren’t being used

a lack of functionality or an excess of it.

Problems With Reliability Having trouble connecting to the API and receiving a response from it.

Concerns Regarding Safety

Problems with multiple threads

Concerns Regarding Performance The response time of the API is quite slow.

Warnings and errors that aren’t appropriate for a caller

Handling of valid argument values that is incorrect

Response Data are not organised in the correct format (JSON or XML)

Automating API Tests: A Step-by-Step Guide

The following tutorials present an in-depth guide to the automation of API testing.

How to put API through its paces with REST Assured

How to put API through its paces using Postman

How to put API through its paces using UFT

In addition, there are other tools available for testing APIs. Have a look at them here.

The Difficulties in Testing APIs

API testing presents a number of challenges, including:

The most difficult aspects of testing a Web API are the parameter combinations, the parameter selections, and the call sequences.

Because there is no graphical user interface (GUI) available for testing the application, it is difficult to provide input values.

The process of validating and verifying the output in a different system can be somewhat challenging for testers.

The testers are required to have knowledge regarding the selection and categorization of the parameters.

Testing is required for the function that handles exceptions.

Testers need to be familiar with coding in order to be successful.


The application programming interface (API) is made up of a group of classes, functions, and procedures that stand in for the business logic layer. If the API is not properly tested, it may cause problems not only in the application that uses the API but also in the application that uses the API. In the field of software engineering, this test is required at all times.