Automation Testing

Is Selenium API Testing Possible?

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A person contemplating with a hand on their chin against a background split into blue and yellow halves, with a "Selenium" checkmark logo on the left and an "API Testing" speech bubble on

Selenium automates browsers. It allows software developers to interact with web browsers in order to automatically test their applications. But can you use Selenium testing for API testing? Is Selenium API testing even possible?

Read on to learn:

  • API testing
  • Incorporating API testing with Selenium testing functional tests
  • If Selenium is great for API Testing

INDEX

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APIs and Automated Testing

One question that came up during this year's Automation Guild session on Testing RESTful APIs with Rest-Assured with Bas Dijkstra was whether you can use Selenium for API testing.

This is actually a question that, surprisingly, I get asked all the time.

But I liked Bas's answer in our Test Guild Automation Podcast interview and during the Automation Guild Conference so much that I decided to share it with you.

How Do I Incorporate API Testing With My Selenium Testing Functional Tests

As I mentioned, whenever I talk about API testing, one question that probably comes to mind to most testers is, can I use Selenium for API testing, and if not, how do I incorporate API testing with my functional tests?

Bas pointed out that he actually wrote a blog post on this fairly recently on what Selenium is and what it is not. Because he also sees this question quite often, surprisingly often on media such as LinkedIn or specialized test automation forums and Twitter even.

For anybody who knows a little about Selenium webdriver that it's a … I'm not even calling it a test tool per se because it's a browser automation tool that simulates the interaction of a user with a browser. It does not simulate the interaction of a user of a system we make.

API testing has specific requirements and nuances that are better addressed by specialized API testing tools such as RestAssured, JMeter, and BlazeMeter. These tools were purpose-built with an understanding of the unique needs of API testing and automation.

Selenium is specifically designed to automate web browsers, not APIs.

The creators of Selenium highlight this distinction by stating that Selenium automates browsers, not APIs. Therefore, while Selenium is excellent for UI testing and interactions with web elements, using it for API testing can be inefficient and may not yield accurate and meaningful results.

To ensure comprehensive and effective API testing, teams are recommended to leverage tools dedicated to API testing, as they are tailored to meet the specific demands of testing APIs.

Selenium Is Not a Tool for API Testing

That should make it pretty clear that Selenium is not a tool for API testing.

Well, of course, if you have a user interface-based or custom framework which is built around the Selenium web browser, you could easily extend that framework to include API testing, but you need a different tool or library for doing that.

One of those libraries that Bas uses is Rest-assured. The Serenity framework also has nice integration for Selenium Testing and Rest-Assured, which you should check out.

make sure to check out my full list of the best open soure API testing tools as well.

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In what scenarios are Selenium tests considered useless?

Selenium tests may be considered useless in scenarios where the user interface (UI) is absent.

When there are no UI elements present, Selenium, being a browser automation tool, lacks the capability to interact with buttons, fields, or other UI components essential for identifying and testing web elements. In such cases, utilizing API tests could be a more effective approach as they can validate and verify the system functionalities even before the UI components are fully implemented. API tests are helpful as they allow for in-depth testing of the underlying logic and operations of the system without a GUI.

Therefore, when the system is in its early development stages and lacks a visible UI, relying solely on Selenium tests may not yield meaningful results.

How can API tests be utilized even when there is no UI in place?

API tests are invaluable for validating backend services, especially when there's no UI.

These tests interact directly with the application's APIs, allowing you to verify business logic, data responses, and performance issues before a UI is available 1 2 . This method is not only efficient but also accelerates the development process by identifying flaws early on. For instance, you can use API tests to simulate various user behaviors and data inputs to see how your system handles them, ensuring that when the UI is developed, it rests on a well-tested foundation.

API tests can be crucial in verifying and validating the system early in development, even without a user interface. By testing APIs' functioning directly, developers can ensure that their system's core functionality is operating correctly. Unlike UI testing tools like Selenium, API tests don't require graphical elements to function effectively.

Mocking tools, such as Parasoft Virtualize (FREE Community Edition Version), can simulate API responses and interactions during development.

This allows developers to test the integration of different components even before the full API or UI is finalized. This approach enables teams to catch and address issues earlier in the development cycle while laying a solid foundation for a robust and functional system.

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What are the goals of API automation testing?

The goals of API automation testing encompass a broad range of objectives to ensure the precision, functionality, and reliability of software systems. Some primary objectives teams can accomplish through API automation testing include:

1. Validate the correct functioning of multiple APIs within a software system.
2. Analyze the output data from API calls, such as verifying HTTP response codes and bodies, to confirm the accuracy of the tested API with diverse inputs.
3. Modify HTTP request headers and parameters and then verify outcomes.
4. Input both valid and invalid parameter values in post HTTP requests and check the resulting validations.
5. Utilize HTTP methods like GET, PUT, POST, and DELETE on designated API URLs.
6. Confirm that APIs respond correctly in edge cases.
7. To maintain product quality, Implement frequent and swift testing procedures, whether manually or through continuous integration triggers like Jenkins or Azure DevOps pipelines.
8. Minimize debugging efforts by identifying issues closer to their root causes.
9. Test the system at an earlier stage of development, even without a user interface.
10. Automatically generate API documentation from the API specification to enhance understanding and usability.

How do API testing tools differ from Selenium in terms of weight and speed?

API testing tools differ from Selenium in terms of weight and speed by being lightweight and faster in comparison. Unlike Selenium, which may require more resources and time to execute tests, API testing tools offer a more efficient approach. Their lightweight nature allows for quick execution of API tests without extensive resources, ultimately leading to faster testing processes.

This difference in weight and speed makes API testing tools a cost-effective and time-saving solution for improving product quality compared to Selenium.

Why may Selenium tests not be the best choice for automated runs via CI/CD pipelines?

You always want to have some e2e automated functional UI tests BUT they should not be 100% of your tests that you run in CI/CD.

Selenium tests or any other functional testing tool may not be optimal for automated runs via CI/CD pipelines due to their heavy and sluggish nature. These characteristics can hinder the efficiency and speed of the testing process within a continuous integration and deployment environment.

Selenium tests and API tests differ significantly in terms of speed and dependencies. Selenium tests, which involve a browser and a corresponding browser driver, are typically slower and more resource-intensive compared to API tests. This is mainly due to the dependencies required for Selenium tests, such as the correct browser version and the specific browser driver (e.g., Chrome Driver, Firefox Driver).

API test help here as well.

How?

The dependencies for tools like Selenium are unnecessary for API testing, making API tests faster and more efficient in terms of execution speed.

And because APIs tests run faster and more reliably they give you and your developers faster feedback during code commits.

For More API Testing Awesomeness

We have a bunch of free courses around API testing, mocking and virtualization to get you up to speed with success.

Be sure to check them out for example we have courses on Hands-On Guide to API Testing with KarateTest the Untestable Using the Power of API Simulation and more!

Free API Testing Courses

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