What’s API testing? A Beginner’s guide Definition, principles and benefits.

An API is a software intermediary, or go-between, that enables two apps to communicate with each other. For example, every time you interact on Facebook, purchase a product on Amazon, or check the news on your phone, APIs are at work. An API operates like this: when you utilize an application on your computer or phone, the app connects to the Internet, sending your data to the server. The server downloads the information, interprets it as needed for the app, then returns a response to the phone or computer in a way that you can understand and use it. APIs are designed for developers to use. They are, in essence, coding tool that allows your application to communicate with other applications. APIs allow you to integrate third-party applications into your work or use your own data and processes in the cloud. The functionality of any application is defined by the connection it has with the outside world. For this reason, connecting your application with APIs becomes very helpful. In today's development process, APIs have become an essential part in web and mobile applications. They enable communication of different components of these systems and help you access data and services. A very important thing to keep in mind is that when dealing with APIs, you need to be sure everything works properly and that you get the correct feedback before integrating them into your applications. That's why testing them is essential. For this reason, a vital part of testing any type of software requires evaluating whether or not there's a way the app can be broken. In order to ensure a certain level of continuity when using an API in multiple ways simultaneously, you need to conduct API testing.

API testing is the process of sending requests to an API and monitoring the responses to ensure its behaving as expected. API testing is designed to assess the functionality, reliability, performance, and security of an API, and is therefore an essential part of the API development lifecycle. Software application development is dominated by the three-layered architecture approach, which is an architecture made up of a presentation layer, business logic layer, and database layer. The business logic layer contains the core functionality, or components, of the application. It must take information inputted by the user from the presentation layer, query the database layer and transform that data according to the business logic, and present the results back to the user via the presentation layer. But the business logic layer must also communicate with other applications as well as human users. To do so, it uses an API. So API testing is designed to validate the business logic as well as the performance, security, and other aspects of the application. API testing does not focus on the individual components of an application, like unit testing, or the look and feel of the application, like user interface (UI) testing, but on what the application does.

You can conduct API testing manually or automatically, and it is often considered a part of integration testing.

·         Manual API testing involves directly interacting with the API using tools like Postman, API Tester or any other available online tools.

·         Automated API testing uses specialized software to send requests to the API and then compares the results to the expected behavior.

API testing is important because it helps ensure that the various components of a system are working together as expected. By verifying the functionality of the API, you can be confident that the system as a whole will function as intended.

What is the difference between automated testing versus manual testing?

Automated testing requires you to use a testing tool, like SoapUI, while manual testing consists of writing your own code to test the API. API testing is one of the areas where automated testing is highly recommended, particularly in the world of DevOps, agile development, and continuous delivery cycles.

You should use manual testing when performing the following tests:

• Exploratory testing
• Usability testing
• Ad-hoc testing

You should use automated testing for the following:

• API functional testing
• Dynamic testing
• Repeated test design
• Analyzing your functional test coverage to know what you're missing
• Performance testing
• Testing protocols in a single, unified framework
• Data driven testing
• Load testing
• Error testing
• Testing in multiple languages
• Regression testing

Of course, automated API testing can be performed in many more cases than this, most importantly, when you are pressed for time.  API testing automation even allows you to test in tandem with development.

API usability testing should continue be a manual testing priority, making sure to create a better, simpler, developer experience. 

If you're looking for an quick and easy manual testing experience, try out the new tool from our friends over at Swagger, Swagger Inspector. It's a super easy to use testing tool that you can use right in your browser. 

API Testing Principles

Having a set of standard rules is the best way to ensure the quality of your APIs and their implementations. You can apply these rules during testing, coding, and development, as well as in production. Here are some principles that you should keep in mind:

·         API testing should be a part of your continuous integration and delivery pipeline.

·         API tests should be easy to maintain and write.

·         A well-designed API will make your tests easier to write.

·         You should test at the boundary of your system.

·         Keep your tests small and focused.

·         Make sure your tests are deterministic.

·         Run your tests in parallel for speed.

·         Use the available and freely accessible tools to simplify API testing.

The first part of API testing involves setting up a testing environment, with the required set of parameters around the API. This involves configuring the database and server for the application’s requirements.

Once you’ve set up your API testing environment, make an API call right away to make sure nothing is broken before you go forward to start your more thorough testing.

You can start combining your application data with your API tests to ensure that the API performs as expected against possible known input configurations.

Next, you need to organize yourself around the API test. Start by asking yourself these questions:

·         Who is your target audience? Who is your API consumer?

·         What environment/s should the API typically be used?

·         What aspects are you testing?

·         What problems are we testing for?

·         What are your priorities to test?

·         What is supposed to happen in normal circumstances?

·         What could potentially happen in abnormal circumstances?

·         What is defined as a Pass or a Fail? What data is the desired output? What is the chain of events?

·         What other APIs could this API interact with?

·         Who on your team is in charge of testing what?

After you’ve created these testing boundaries and requirements, you need to decide what you want to test your API for.

API Testing Best Practices

Before you head off on your own and get started with API testing of your very own, here are the top 10 tips we want you to remember when API testing!

1.      Test for the typical or expected results first

2.      Add stress to the system through a series of API load tests

3.      Test for failure. Make sure you understand how your API will fail. Just make sure the API fails consistently and gracefully

4.      Group test cases by test category

5.      Prioritize API function calls so that it will be easy for testers to test quickly and easily

6.      Limit the tests from as many variables as possible by keeping it as isolated as possible

7.      See how it handles unforeseen problems and loads by throwing as much as you can at it

8.      Perform well-planned call sequencing

9.      For complete test coverage, create test cases for all possible API input combinations

How to Start API Testing

There are many different types of tests you can perform on your APIs:

·         Functionality tests focus on ensuring that the API is able to perform its intended functions.

·         Performance tests measure the response times of the API and check for bottlenecks.

·         Security tests assess the vulnerability of the API to attack vectors such as SQL injection and cross-site scripting (XSS).

·         To get started with API testing, you will need to have access to an application with an exposed API. You will also need to choose a method for sending requests to the API (manual or automated), and select a tool or framework for writing your tests (if using automated testing).

Once you have these things set up, you can begin writing your test cases and running them against the API.

Benefits of API Testing

When we perform our API testing, one of the biggest benefits we can enjoy is that we can often test early. This is because the API component is often developed before the UI component which allows for Swiffer feedback as well and it can help steer development on the components that integrate with our API or even adept our API if need be. API testing is also a lot cheaper than manual e2e testing or automated UI testing because we can create much more fine grained component tests that we do not have to repeat every as often as our end-to-end scenarios. All of these benefits allow us to leave enough room for security testing where it is most impactful, the API level. Security testing on all levels is useful of course but we do not live in a world with endless budgets so we have to put our priorities in order. If we have tested our APIs well and documented them properly, we can allow for a much smoother integration and we can ensure that whatever interface subscribes to our API, they are well informed and ensured of a tested API.

Like we get a lot of advantages by using APIs in application, similarly by performing API testing we achieve a lot of things towards the success of the developed application. Below are some of the benefits i.e.

·         Earlier validation of correctness in response and data.

·         Earlier test maintenance.

·         Better speed and coverage of testing.

·         GUI independent testing.

·         Reduced testing cost.

·         Language independent test.

·         Helpful in testing core functionality.

API Testing Tips

API testing can be a challenge, but regardless of the tools you decide to use here are some tips that can help:

·         Make sure you have a clear understanding of the API before you start testing. Read the documentation and any other available materials. This will help you know what to expect and how the API should work.

·         Use API testing tools: This will give you a better understanding of how the API works and make it easier to find any issues.

·         Test all aspects of the API, including input validation, error handling, and security. These are all important factors in ensuring that your API is working correctly.

·         Keep your tests up-to-date as the API changes. This will help ensure that you catch any new issues that may arise.

·         Use mobile apps for API testing. Things are changing all the time these days, where many people are working remotely, and from their phones too. By using mobile apps you can increase your productivity, become more mobile, and work from anywhere in the world. A good example of such a tool is the API Tester.

By following these tips, you can help make sure that your API testing is effective and efficient.

Conclusion

API testing is a key part of ensuring the quality of your software. By following these highlighted rules you will be able to ensure your tests are functional, secure and have a reliable performance. As more and more services that we use every day rely on hundreds of different interconnected APIs, API testing is expected to increase in order to assure that these APIs and the software they connect work as intended. It’s important to understand what API testing is and how to conduct it in order to stay connected in this digital economy and release products faster.