Below are concepts of the basic API Testing
What is an API?
API stands for Application Programming Interface, is a software mediator that allows communication between two applications to interact with each other.
Suppose you are looking for a Hotel booking on online Travel domain application. While Searching, you will fill the Information like City, Check-In date, Check-Out Date and Number of Guests. Then you will click Search Button. But, what is happening between submitting the form and getting the Hotel Details. The application gathers details from different hotels. When you click on “search,” the application then connects with each hotel’s API, which shows the results for available rooms matching with your search Criteria
But, if an API does not work Properly, it will never be acquired, nevertheless if it is free or not. To avoid that, API’s are tested before they are used.
What is API (Application Programming Interface) Testing?
We perform API testing as a type of software testing to test Application Programming Interface (APIs) and verify if they meet assumptions for functionality, reliability, performance, and security.
In other words, API testing aims to find bugs, inconsistencies, or variations from the expected behavior of an API.. Basically, applications have three different layers:
- Presentation Layer
- Business Layer
- Database Layer
API testing is done at the most crucial layer of software application i.e. the Business Layer. In the business layer, all transactions between User Interface (UI) and database occur. So, to ensure that, API provide complete functionality for easy future expansion of the software application.
Need of API Testing:
API testing is a crucial process that QA teams should focus on. It offers a few advantages over other types of testing
Language Independent: XML and JSON enable the transfer of data, facilitating automation in any language, irrespective of the programming languages used in the application’s development.
GUI Independent: We perform API testing to verify the main functionality of the application, identify small errors, and assess the quality of a build. API testing can be conducted without a user interface.
Improved Test Coverage: Most API’s have features, that helps a tester to create automated tests with high test coverage including positive and negative cases. We can rarely find test cases that cannot be automated.
Reduce Testing Cost: With API testing we can find bugs before the GUI of the application is ready. Generally, these bugs will become bigger during GUI testing. So, detecting those bugs while doing API testing will reduce cost of bug fix.
Enables Faster Releases: The test cases that take around 8-10 hrs executing UI regression testing take only around 1-2 hrs with API testing. This helps companies to release builds faster with API testing.
How to Perform
Below are the steps that we follow to perform API testing:
API (Application Programming Interface) Specification Review
The First step to test API is to create the document for API Testing requirements. What is purpose of API? Workflow of application? What Integration supported by API? What are the various Features of API? This API Document will help you planning API Testing throughout the Testing process
Setting Up Test Environment
Second step in this is to create the test Environment, with required set of components in the API. This involves configuring the database and server for the application requirements.
Integrating Application Data
During this step, we combine Application with API tests to make sure that the API functions as expected.
Deciding Type of API Test
After creating testing Boundaries, you decide what you want to test your API for.
Test Execution & Reporting
Once you decide what to test the API for, the next step is to create test cases around that requirements and execute them. Types of API Testing
In API testing, you can perform the following types of testing:
- Functionality Testing – We verify if the API works and performs exactly as intended.
- Reliability Testing – We verify if the API can be uniformly connected to and yield stable results.
- Validation Testing – It checks the aspects of application, behaviour, and efficiency of an API
- Load Testing – We do it to ensure the performance of the API under both normal and high load conditions.
- UI Testing – It includes testing the user interface for the API and other important parts
- Security Testing – To verify that the API is secure against all possible threats
- Penetration Testing – To detect vulnerabilities in an application from an attacker
- Fuzz Testing – To verify the API in terms of the limits to prepare for the “worst case scenarios”
The most commonly performed API test types are the ones mentioned above. By performing these tests What will you find?
You are validating:
- Duplicate or missing functionality
- Improper messaging
- Error handling mechanism is incompatible
- Multi-threaded issues
- Security, performance & security issues
- Reliability issues
As API Testing is acquiring popularity, we have many API Testing tools available in the market for the same. Below are some of the API Testing tools:
Here are some Tools
For performing API testing, you will require a tool to organize and run your test cases. Following are some of the API testing tools which can be used for Rest and Soap API:
SoapUI: It is the one of the most popular open-source tools for API testing. With SoapUI you can perform functional testing, performance testing, security testing, and data-driven testing. It gives the reports for testing and allow to export the data.
Postman: Additionally, it is one of the most popular testing tools with more than 4 million users worldwide. It is compatible with Mac, Windows, Linux & Chrome Apps. It allows you to set up all the headers and cookies your API expects, and then verifies the response.
Katalon Studio: It is a robust and complete automation tool for API, Web, and mobile testing. Gives easy deployment by including all frameworks, ALM integrations, and plugins in one package. It supports both SOAP and REST requests, along with various types of commands and parameterization functionalities.
REST–assured: It is an open-source Java Domain-specific language (DSL) tool for Rest testing which makes testing REST service simple. Compatible with XML and JSON requests.
Challenges of this:
- It does not have GUI, so it difficult for testers to give input values
- Test case management is a difficult process as tester might have to deal with large number of test cases
- The tester should possess expertise in the programming language(s) targeted by the API.
- It is Time-consuming as it need a lot of time and resources to develop tools and design tests
- Thorough testing is necessary for exception handling functions.
However, despite the challenges that we face, testing is quite crucial and highly required. If errors are not observed and an API breaks, it can not only break a single application but also disrupt an entire chain of application processes connected to it.
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