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What is API testing? Advantages of API testing

8 Apr
4 Min
Api Testing

Table of content

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    Table of Contents
    1. What is API?
    2. Advantages of API testing services
    3. Top Tools for the API Testing

    Before going for API testing, let’s have a quick look at the brief introduction of API.

    What is API?

    Basically, API is a connecting source that enables the exchange of information between two different applications. In more simplified term, the function of API is to deliver the user’s response to the application, and send application’s response to the user. Furthermore, API is a collection of functions that enables applications to interact with the microservices, operating systems and other components of an existing software.  

    You can check out this example: We all are quite used to making online payments through various modes like Internet Banking, UPI, Wallets, etc. This is an application of Payment Gateway API. Here, you will get to know about the concepts of API testing services, processes, and benefits of API testing.

    What is API Testing:

    To validate the performance, reliability, and security of the Application Programming Interface (API), the QA team follows the API testing method. Also, the main objective of API testing is to verify the responsiveness and functional behavior of the API under various scenarios.  During API testing, testers prefer to use software to send calls to the APIs and validates their performance.

    Also, they make a note of the system’s response. Moreover, during the process, the team keeps all the attention on the business logic layer rather than the look & feel, etc.  Furthermore, to deliver accurate outputs, you must examine the APIs, and hence knowing about the API testing process is a must.

    Why does API Testing need to perform?

    If you are thinking about the need for API testing, the following section will help you. We are living in a time where users expect everything ready. This is the reason; IT companies are inclining towards the concept of microservices.  Moreover, microservices facilitate different datastores corresponding to each section of the application that requires different commands for operations.

    Companies prefer to use the concept of microservices because it allows quick deployment which further makes the development process smoother. However, we have shared the concept of microservices because APIs play an important role here. Each section of the applications gets commands through the API only.

    Now you must be able to connect microservices and APIs.  Hence, API testing is a must to do because it helps to identify the errors or bugs at the very early stage of development. Also, through API testing, we get to know whether the API is effectively interacting with all the sections of the code or not? Here, testers validate the response of the API.  

    Furthermore, you must have heard, “Sooner is better” and the same goes here. Finding bugs at the earlier stages, always make the application more productive and robust. Also, it protects the application from further damages. Because of these important reasons, one should definitely go for the API testing process. Also, the mobile API testing is equally significant.

    Do you know about API Testing in the test pyramid?

    If you are investing more than expected time waiting on the test suite to run? Also, if there is a scenario in which you are rerunning the test suits because it fails every time? If you are experiencing these kinds of issues, you are missing the test pyramid. Basically, the test pyramid is a framework that helps developers to bring quality to the product.

    It acts as a guide to make an application robust and fast which further drives them towards the reliable test suite.  Being a leading API testing company, we always recommend including the test pyramid because it offers immediate feedback to the development team that the updated code will not damage the existing features of the application.

    As a result, the developer takes the decision either to move ahead with the code or not which further helps in saving time and building the robust platform.

    Levels of Pyramid Testing

    Moreover, the test pyramid consists of three levels. The pyramid name is given because of this structural flow.

    • Lowest level: Unit testing.
    • Middle tier: Integration testing.
    • Top-level: End-to-end testing.

    Also, the implementation of the test pyramid reduces your waiting time that you spend for a test suite to run.

    Advantages of API testing services:

    So far, you know about API testing and the reasons why we use it. Now here we will get to know about some concrete advantages of the running API testing process:

    1. Saves Time:

    Do you think we need to explain the worth of time? In such a competitive time, if you are not smartly optimizing your time, you will be lagging. Through API testing services testers save time because API testing always takes lesser time as compared to GUI functional testing.  For instance: If we compare both the concepts practically, we find the worth of API testing.  

    Suppose you are running 40,000 automated API tests, it will take only 10-12 hours whereas if you perform the same activity for GUI tests it will take 65 hours approximately. Big difference guys, we can do lots of productive tasks such as marketing in the saved hours. Moreover, when API testing is saving time, will automatically save your cost. Hence acknowledge API testing benefits and plan the execution accordingly.

    2. No dependency on programming language:

    During API testing, the exchange of data takes place using XML or JASON. So in order to perform the activity, the testing team is free to select any core language.

    Also, it does not demand too much technical knowledge. If you know, how to perform testing that is enough.

    3.Earlier identification of the bugs:

    This is one of the main API testing benefits because it increases the productivity of the application by saving cost and time both. Also, when the developer gets bugs at the initial stages, they resolve them more efficiently.  

    Moreover, as we know codes are always interrelated with each other and a small bug can be a bigger issue at the later stages. Also, resolving them becomes complex and takes time as well.  So these are the API testing benefits and one should always include API testing prior to delivering an application to the client.

    Top Tools for the API Testing

    1. Postman

    Testers who are not comfortable dealing with the code in an IDE using the developer’s programming language should go for Postman. It is the tool to perform API testing. Basically, Postman was only a Chrome browser plugin and by this, it has extended its limits. The tool offers their solution for Windows as well as Mac.

    Advantages of Postman

    • No need to learn the new programming language.
    • An interactive interface that makes it easy to understand.
    • Supports maximum OS (operating systems) like Windows, Mac, Linux, etc.
    • Facilitates features of Run, Test, Monitor, and Document.
    • Easy KT (Knowledge Transfer) process.

    2. Rest Assured

    For those who are looking for API testing in Java language only, Rest Assured will be a reliable option. Also, it is open-source and one can efficiently work on it. Moreover, in order to use the API testing tool, one should not be an HTTP expert.

    Advantages of Rest Assured

    • The tool is available with in-built functions and you are not required to write code from scratch.
    • In order to test the Web APIs, no expertise in HTTP is required.
    • Rest Assured supports BDD (Behavior Driven Development) testing.

    3. Katalon Studio:

    Katalon Studio facilitates end-to-end testing services and hence became the leading tool for API testing. Also, it offers solutions for programmers as well as testers. Moreover, the team prefers to use it because it is free and one can test even Desktop Apps, Web Apps, and Mobile Apps. Actually, Katalon Studio is an emerging API testing tool that supports SOAP and REST requests.

    Advantages of Katalon Studio:

    • It supports CI/DC Integration.
    • Katalon Studio is based on the data-driven concept.
    • Supports SOAP as well as REST APIs.
    • Works well across multiple operating systems like Mac, Windows, and Linux.
    • Non-technical person can also work on the tool comfortably.

    4. SoapUI:

    When you are finding yourself in the most complicated scenario during API testing, simply for SOAP API. It helps developers to execute tests for Web Services, REST, and SOAP APIs. The tool is dedicatedly built for API testing that creates custom codes by the use of Groovy. The tool becomes easier to access because of its drag and drop feature.

    Advantages of SOAP API:

    • One can test the most complex scenario with the help of the tool.
    • Exclusively for API testing.
    • Supports asynchronous testing.
    • Easy to run test cases.

    5. PAW

    An API testing tool that is designed for MAC operating systems. Whether you are an API user or a creator, PAW will be useful for you anyway. It helps to create HTTP requests. Also, with the help of PAW, testers will be able to examine the response from the server. Moreover, it allows the QA team to generate the client codes as well. These magnificent features make it the leading API testing tool for MAC.

    Advantages of PAW:

    • Enrich with an interactive and attractive interface.
    • Very easy to learn and perform testing.
    • Gives concrete performance as compared to other API testing tools.
    • It holds the feature of multi-dimensional settings.

    6. JMeter

    By seeing this name, you must be thinking about load testing. You are right. Initially, JMeter was created to perform load testing but because of its extra features, people start using it for API testing as well. Also, it performed well and that is why still in trend. The additional features of JMeter make API testing easier and result-oriented.

    Advantages of JMeter

    • Enrich with features to test API as well as performance.
    • Reduces testing efforts.
    • Supports Jenkins so can be integrated with the CI pipelines.

    7. Karate DSL

    With powerful assertion capabilities here comes another API testing tool. Karate DSL is an open-source framework based on the cucumber library. The API testing tool helps to create environments for API-based BDD tests using simple methods. Here, no need to write long step-by-step definitions in order to execute the run.

    Advantages of Karate DSL

    • Karate DSL supports configuration switching.
    • For API testing, it allows reusing of payload-data.
    • The tool supports multi-thread parallel execution.
    • Simple and easy to execute tests.

    8. Assertible

    If you are looking for a reliable API testing tool, Assertible can also be an option. It follows CI (Continuous Integration) and delivery pipeline for automated API tests. Also, the testing tool supports GitHub, Slack, and Zapier.

    Assertible has a Sync feature that allows testers to update their tests automatically if any change is made in their specification. A new feature was introduced to Assertible in Oct 2019 which we call Encrypted Variable. Here, you get a new and secure way to store passwords, tokens, and data which further improves the performance of the APIs.

    Advantages of Assertible

    • Offers validation of HTTP responses.
    • Keeps JSON Path integrity tests.
    • No manual intervention is needed towards any change in specification.

    ROI for the API Testing?

    We at QAble a leading API testing company across the globe and by using our experience we are highlighting the ROI of API testing.

    By reading the above content, you must have understood the worth of web API testing as well as mobile API testing. Also, we understand, building a product and launching it in the market is not everyone’s cup of tea and hence you need to be smart to make your product smart. If you follow the right approach and strategies from development to execution you will get the best returns on your investment. By following the API testing process, you will be able to

    • Generate more time to market the product.
    • Gain client’s trust easily.
    • Save time and save cost.
    • Make your application more productive.
    • Maximize the revenue.


    Hence always give priority to API testing. Also, if you are looking for the most prominent API testing company, QAble will be on the top. Feel free to share your queries. We will be more than happy to assist.

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    Written by Nishil Patel

    CEO & Founder

    Nishil is a successful serial entrepreneur. He has more than a decade of experience in the software industry. He advocates for a culture of excellence in every software product.


    What are the 4 method API testing?

    Four methods form the foundation of API testing: GET retrieves data, POST creates or submits new data, PUT updates existing data, and DELETE removes data. These methods allow us to interact with and test the behavior of various API endpoints.

    What is API testing done for?

    API testing safeguards the quality and functionality of our applications by verifying their data exchange, assessing reliability under load, identifying security weaknesses, and optimizing performance. It's an essential step to ensure our applications function as intended and interact seamlessly with other systems.

    What are advantages and disadvantages of API testing?

    On the positive side, it enables early bug detection, improved code quality, enhanced security, and faster development through parallel testing. However, it has limitations, including limited scope (excluding UI/UX), complexity, and dependence on accurate documentation. A balanced testing strategy should consider both API testing and other methods for holistic quality assurance.

    What is importance of API testing?

    API testing is vital for building secure and dependable applications. It guarantees the API delivers accurate data, functions as designed, and safeguards sensitive information through vulnerability detection. It also optimizes performance to handle real-world user interactions effectively. By proactively addressing these areas, API testing empowers us to build applications with confidence.

    How API testing benefits you.

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