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API testing goals – What types of tests can we design?

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Software development teams now understand the importance of API development and testing. It has helped grow the culture of shift-left testing, amplifying speed and improving the quality of product delivered to the customer. API tests effortlessly sync with the continuous testing, agile, and DevOps principles as well.

Thanks to the fact that several user-friendly API testing tools have emerged, more are now imbibed by software dev projects. Some devices even offer codeless options and provide easy-to-use interfaces, community support, and easy-to-understand tutorials. And the automation testing guide will help QA teams get started on this journey.

This article speaks to the API testing goals and some popular tools that SDLC-based projects can use. We know that API tests involve sending data through APIs and verifying the data generated at the base. There are more goals we can build tests on, and this is what we will explore here.

API testing goals – what can we test?

Remember that API tests function to interact with the product’s backend for test outputs and business logic verification. Tests’ design should also be around the atomicity, consistency, isolation, and durability factors.

API tests help verify various product factors while connecting, transferring data, and associating business logic across multiple systems and applications. They can perform tests for boundary conditions, recognizing errors, input parameter validations, and more.

This article describes several testing types that can be performed using API testing. We also note a few popular test automation tools as a bonus to help your project get started.

Test for the functionality of the product

In the case of use-case scenarios in which the testing of the product’s functionality is involved, API tests rely on verifying the mapping data between the frontend and the backend. Using user-friendly tools, one can test the functionality of the endpoints of the API. Functional tests, after all, should not stop at the GUI level.

For example, some possible tests to check for functionality:

  • Verify that when we add or delete items in the shopping cart, the overall item count is updated accordingly.
  • Click a button and verify it makes changes to the database data.

Test for reliability of the programming interfaces

Projects can use API tests to verify if the product remains failure-free for a predetermined period in a test, operational, or production environment. Using the test results, one can assess failure patterns, the root cause of failure, and more.

Test for performance of the programming interfaces

These non-functional tests verify how the application behaves under stress, load, and more. For example:

  • When a high number of users interact with the online shopping application, does the application crash?

Here, QA teams rely on virtual users for testing APIs. Eventually, it is easy to simulate load artificially and measure how the environment handles the situation.

In the load testing case, the load is increased on the application using API tests to check how the system behaves. Accordingly, the response time, throughput, etc., can be monitored using the API requests’ responses.

Test for security of the programming interfaces

These non-functional security auditing tests include options to verify the authentication, authorization, and access control capabilities of the product. For example, we could have scenarios to test deadlocks, data corruption, data loss situations, and more. Therefore, using the test results, projects can verify 3rd party or public APIs and check for internal APIs’ vulnerability. Also, penetration and fuzz testing come within the scope of security testing using API tests.

Test for runtime errors

In this case, we monitor the APIs’ run execution rather than only relying on its test results. As the API runs, the QA tester monitors it for handler failures, implementation and performance errors, etc.  Also, while it runs, resource and memory leaks are observed, if any. In the process, the QA team imparts known scenarios that cause failures to verify if the product can appropriately detect the errors, manage the errors, and take action accordingly.

Validation testing

In the product’s testing process’s final steps, the QA team can perform validation tests on the product using API tests to verify the product behavior, efficiency, etc. Eventually, it assures the quality of the final product to be delivered to the customer. Finally, it helps confirm if the team built the correct product as per the defined behavior.

Testing for interoperability

API tests can also verify the conventions for Web Services Interoperability. As a result of the tests, the QA team can check if the product can interact and integrate with external components without interoperability issues.

Popular automation testing tools for API testing

QA testers can perform API tests using API testing tools. The tools listed below feature user-friendly UI, and one can quickly write tests based on the responses of the requests sent utilizing the interface.


TestProject is a free-to-use end to end test automation platform that supports API testing as one of the test solutions. The tool has a  RESTful API Client Addon, which empowers testers to use REST APIs in test suites. QA test automation developers can integrate API and UI calls in the test scripts as well.


This tool is popularly known for its API development capabilities. It is used for testing APIs, wherein for test case scenarios such as exploratory testing, one can send different data inputs to analyze the returned value outputs. This platform helps teams automate manual test scenarios and integrate them into the CI/CD pipeline with ease.


This API test automation tool has both open-source and commercial versions. It is easy to create, manage, execute end to end test cases on REST, SOAP, JDBC, and other web services.

Wrapping up

While aiming for the API testing goals, software development projects ought to have a 360-degree outlook into exploring the several types of tests that API tests can help automate. It is necessary to choose reliable test automation tools that support your team on their test automation journey. A tool that helps speed up the delivery process can benefit both the customer and the organization building the software.

API testing is vital for product quality and continuous integration/continuous deployment processes, crucial for all software development organizations and customers. A well-designed, produced, and tested API is a must.

More on this topic:

The Six Rules of REST APIs

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