How to test your APIs – Best Practices

API (Application Programming Interface) testing is an essential part of the software development process, as it helps make sure that your APIs provide the expected results, and are reliable, performant, and secure.

In this blog, we’ll cover the basics of API testing, best practices, and how to test your APIs. 

What is an API?

An API is a set of programming instructions that allows different software systems to communicate with each other. It’s basically the connection between different systems or applications.

For example, at Koderly we develop APIs which are used by a customer’s website. The API communicates with the database layer providing key information to populate the presentation layer. In addition, the API can communicate with other third-party APIs, such as a payment provider to facilitate the processing of payments.  

how to test your APIs - best practices - What is API testing? Image

How to test your APIs - best practices

Now that we have a basic understanding of what an API is, let’s look at why API testing is important.

API testing makes sure that your APIs are reliable, efficient, and secure. It also helps to identify any potential bugs or issues with your APIs before they become a problem for your users (we’ll discuss the benefits of API testing later in this blog).

Here are some best practices for how to test your APIs:

1. Understand your API

You should start with a clear understanding of your API’s functionality and expected results. Ask yourself, does the API have sufficient documentation, and is it clear?

Understanding what the API is capable of will help you create a comprehensive test plan and ensure that you are testing all the relevant functionality.

2. Set-up your test environment

It’s vital that your testing environment is separate from your production environment. A suitable test environment will allow you to make changes safely and test out different configurations without affecting your live API.

3. Use API testing tools

There are many tools available that can help you automate the testing of your APIs, which can save you time and effort. This article, lists the top 10 API testing tools of 2023.

4. Test the different layers separately

This includes the user interface, the business logic, and the database layers, as mentioned above.

This will help you identify any issues at the specific layer, rather than having to troubleshoot issues across multiple layers.

5. Use positive and negative test cases

Positive test cases involve testing the API with valid input and verifying that the expected output is returned.

Negative test cases involve testing the API with invalid input and verifying that the API returns the appropriate error message.

6. User a variety of test data

You need to make sure that your API is handling all types of input correctly. This includes testing with different data types (e.g. strings, integers, booleans), different lengths of input, and different combinations of input.

7. Monitor the performance of your API during testing

This includes monitoring the response time of the API and checking for any performance issues.

8. Documenting your test results and any issues

This will help you keep track of your progress and identify any recurring issues that need to be addressed.

Benefits of API testing

Performing API testing has several benefits, here are just a few that stand out:

1. Early detection of defects

API testing enables testers to identify defects in the software application or system early in the development cycle. This helps reduce the cost of fixing bugs and improved the overall quality of the software.

How to test your APIs - benefits of API testing - Detect defects

2. Improved test coverage

API testing provides the ability to test a wider range of scenarios in a short amount of time. This means that more functionalities can be covered by the tests, resulting in better overall test coverage.

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3. Increased productivity

Since API testing can be automated, it can be run quickly and repeatedly without requiring manual intervention. This helps increase the productivity of the development and testing teams.

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4. Better collaboration

API testing provides a common ground for developers and testers to collaborate, share knowledge, and ensure that the system works as expected.

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5. Reduced risk

By thoroughly testing the interface, API testing helps to reduce the risk of unexpected behaviour or data loss. This ensures that the system is reliable and provides a positive integration experience.

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API testing is an important part of the software development process, and following these best practices can help you ensure that your APIs are reliable, performant, and secure. By thoroughly testing your APIs, you can identify and fix any issues before they become a problem for your users.

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Jeff Ng

Jeff has been working in software and technical support for over 15 years, and has intimate knowledge of our client portfolio and product suite. He's passionate about diagnosing performance issues within SQL Server databases and specialises in migrating software to the cloud or on-premise infrastructure. He offers extensive support for our clients ever-changing needs.