7 Powerful Ways to Improve Your API Tests

It’s no secret that the quality of your API tests can have a massive impact on the amount of money your app makes. So how can you make sure you are getting the best possible results when writing your API tests?

The top 7 API testing best practices are:

  1. pick the proper testing tools
  2. simulate production environment
  3. use real data
  4. test positive and negative scenarios
  5. mock missing API and 3rd party dependencies
  6. continuous API testing
  7. include security and performance tests

This article explains how to improve your API tests and ensure you get the best results.

What is API Testing?

API testing is the process of verifying that the APIs (Application Programming Interface) meet the requirements specified by the stakeholders. The API testing process includes a set of activities that help to ensure the APIs are functioning as expected and meet the requirements for functionality, reliability, performance, and security. In the testing pyramid, API testing belongs to integration testing.

api testing

Testing APIs is vital because APIs are the backbone of most modern software applications. A well-functioning API can help to ensure the success of an application. Conversely, poorly functioning or insecure APIs can lead to various problems for an application, including data loss, system crashes, and security breaches.

There are many ways to test APIs, including manual, automated, and fuzzy testing.

Manual testing is the most basic type of API testing and involves checking the API manually for errors and vulnerabilities. Automated testing automates the process of manual testing and can help find errors that you might miss during manual testing. Fuzzy testing is a more advanced type of test automation that involves sending unexpected data to the API to find security vulnerabilities.

However, not all tests are created equal. To make the most out of your testing efforts, you need to follow the best practices.

#1 Pick the proper API testing tools

API testing tools ensure that the APIs work as expected and help you build reliable and scalable APIs.

There are several factors to consider when choosing the right API testing tool:

  1. Consider is the size and complexity of the API. The tool should be able to handle the complexity of the API and be able to scale with the increasing demand.
  2. Consider the type of required testing. The tool should be able to support both functional and load testing.
  3. Consider the tool’s compatibility with the development process and other tools in use. The tool should be easy to use and integrate into the existing development process.
  4. Consider the cost. The tool should be affordable – you should be able to buy one or two licenses at a time.

Popular API testing tools are Katalon Studio, Apache JMeter, SoapUI, and Postman. API testing tools allow you to test different aspects of APIs. For example, you can test the performance of an API, the functionality of its methods, and its security.

The tools help improve the quality of APIs by identifying bugs before they go live. They also ensure that the APIs are not vulnerable to attacks and data leakage.

#2 Simulate production environment

Testing an API in a simulated production environment is important to ensure that the API is ready for release.

You can create a simulated production environment using various methods, such as a testing server or setting up a test environment cloned from the production environment.

You can also various tools to simulate a production environment by capturing live traffic from the production environment and recreating it in the testing environment.

Once you have tested the API in a simulated production environment, you can release it to the live production environment. If you find any issues in the test environment, they can be quickly addressed and fixed. This helps ensure that the API is functioning properly and meeting the needs of the end-users. 

#3 Use real data while performing API testing

You should perform API testing using real data as much as possible. That will help ensure that the API is functioning properly and that the data passing through it is accurate. Additionally, using real data will help identify potential API issues that may not be evident when testing with simulated data.

To help simulate real data, you can use the API documentation to create dummy data. You can also get sample data from the production environment and anonymize it before using it in testing. If that’s not possible, you may have to spend some time creating data that mimics the actual data.

#4 Test positive and negative scenarios

It is important to test positive and negative scenarios to ensure the API can handle them gracefully. That involves creating fake input data and deliberately attempting to break the API. Tracking the API’s response in each case will help you identify and fix any potential problems.

One common negative testing scenario is an unexpected input. For example, if your API expects a number as input but someone sends a string instead, the API might fail. Testing for this type of scenario and tracking the API’s response can ensure that the API will handle unexpected inputs gracefully.

There are a few benefits to testing positive and negative outcomes and tracking API responses. First, it can help ensure that all aspects of the API are working as expected. Additionally, it can help to improve the overall quality of the API. 

#5 Mock missing API and 3rd party dependencies

It can be difficult to test APIs that use other APIs that haven’t been implemented yet. One way to work around this is to use libraries that create fake objects that you can use in place of the real objects. They can help you test your API without worrying about the missing dependencies. 

When testing an API, it’s important to test all possible use cases. However, that can require more time and money. Also, it can be difficult when the API uses a 3rd party library, for example, a payment gateway. You don’t want to process real payments in your tests, right?

One way to mock 3rd party dependencies is to use a stub. A stub is a dummy implementation of the 3rd party dependency that you can use while testing. It allows you to test your API without calling the 3rd party dependency.

#6 Continuous API testing

When you Include API testing as part of the continuous integration and continuous delivery (CI/CD), the pipeline can help ensure that your APIs function as expected and meet the quality criteria you set. In addition, having continuous testing in place to test your APIs regularly can help you avoid costly and embarrassing outages.

Instead of manually testing your API, you can use a special tool to automate the process. You can use different tools to test your API and highlight any inefficient code that is slowing down the process.

Automating API validation helps ensure that new updates have not broken any other API endpoint. It’s also useful for newcomers who are helping to develop the API as they quickly get up to speed on how the various interfaces work.

#7 Include security and performance tests

The API tests can be the first line of defense against attacks and any security flaws in your application. As more and more people start using APIs on their websites, it becomes more important to test them to ensure they’re secure.

Your API testing strategy should also verify that an API is functioning as intended and is not exposing any security vulnerabilities. API security is critical for the safety of websites and applications that rely on APIs.

Security testing can include fuzzing the input, validating input and output, and verifying authentication and authorization.

Performance tests are often conducted as part of API testing to determine how the API will respond under heavy loads. One common performance issue when using an API is latency, which is the delay between when a request is sent and when the response is received. To reduce latency, it is important to optimize the code that you will use to call the API.

So, don’t forget to monitor the performance of your API. If your API starts to perform poorly, it could be unhappy users and lost revenue.

By including security and performance testing as part of your API testing, you can ensure that your API is secure and efficient, which will help garner the trust of your customers.


API testing, though often neglected, is a critical part of software quality engineering.

The first step in API testing is to create a test suite. It should include both functional and non-functional tests. Functional testing verifies that the API is working as expected, while non-functional testing measures performance and reliability.

Once you have your test suite, you need to run it regularly. The best way to do this is to automate it. Automation testing can help you find problems early before they cause serious damage.

By following some simple best practices, you can go a long way towards ensuring the quality of your API.

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