API Unit Testing - Carefully Analyse APIs Now!

API unit testing isolates & tests individual functionalities, catching bugs early & preventing future headaches. It ensures each API piece works as planned, leading to a more reliable & maintainable system.

Steven Ang Cheong Seng

Steven Ang Cheong Seng

15 May 2025

API Unit Testing - Carefully Analyse APIs Now!

An API's testing phase may be one of the longest and most tedious stages of an API lifecycle. To ensure that no flaws revolve around the API, API developers do their utmost best to remove any problems that an API may exhibit. One of these methods is API unit testing.

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API unit testing can be done with most API tools you can find online - however, some of these tools may be limited due to a paywall, or they just do not have enough features to properly support testing.

Apidog, a comprehensive API development tool, does not have this restriction. Apidog allows users to build, mock, test, and document APIs conveniently within a single app, so you no longer need multiple tools to create an API!

If Apidog sounds like a solution to your API problems, start downloading Apidog today by clicking on the button below! 👇 👇 👇
Apidog An integrated platform for API design, debugging, development, mock, and testing
REAL API Design-first Development Platform. Design. Debug. Test. Document. Mock. Build APIs Faster & Together.
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What is API Unit Testing?

API unit testing is a meticulous approach beyond simply testing an entire API endpoint. API uni testing involves ensuring individual functionalities within an endpoint work as intended, even if these functionalities might interact with other parts of the system.

API unit testing should also not be confused with API health checks and validation testing. Although they both sound like they "test" the APIs to ensure they are running smoothly, they have minute differences!

API Health Check | Routinely Monitor Your APIs
API health checks are like check-ups for your software. Regularly pinging an API endpoint triggers tests, generating a report on functionality & performance. This helps catch issues early, preventing outages and ensuring a smooth user experience.
Validation Testing | What You See is What You Should Get
Thoughtful API validation testing is vital for software development. This ensures API robustness, reliability, and security, fostering trust and facilitating seamless application integrations.

Goals of API Unit Testing

1.Validating Functionality with Precision:

2.Isolation for Focused Scrutiny:

3.Early Bug Detection: Nip it in the Bud:

4.Maintainability:  Building a Documented API:

API Unit Testing Key Aspects

api unit testing pyramid

1.Mocking and Stubbing:

2.Testing Frameworks and Libraries:

3.Assertions:

4.Focus on Functionality, not Implementation:

5.Integration with Development Workflow:

Importance of API Unit Testing

1.Catch Bugs Early, Save Time and Money:

Think of unit tests as quality inspectors for your API. They meticulously examine each endpoint, ensuring it functions as intended with various inputs. This proactive approach helps identify bugs early in the development process before they become bigger issues.  

Imagine finding a tiny crack in a car's windshield during construction versus discovering a shattered one after it rolls off the assembly line – that's the difference between catching bugs early and dealing with them later. Early detection saves time, resources, and frustration for everyone involved.

2.Build Confidence and Embrace Change:

With a comprehensive suite of unit tests in place, developers gain confidence in the API's stability. They can make changes to the codebase knowing that the tests will act as a safety net, catching any regressions or unintended side effects.

This fosters a more agile development environment where innovation and experimentation are encouraged.  Think of it like having a safety harness while rock climbing – it empowers you to explore new features without the fear of a major fall.

3.Deliver a Reliable and Predictable API:

Just like you wouldn't trust a car that sputters and stalls unpredictably, users depend on APIs to function consistently. Unit testing helps ensure your API behaves as expected in different scenarios. This translates to a more reliable and predictable user experience.  

Imagine a vending machine that dispenses the wrong item half the time – that's the frustration users experience with an unreliable API. Unit testing helps avoid such scenarios.

4.Maintain a Clean and Documented Codebase:

Well-written unit tests act as living documentation for your API. They clearly outline the expected behavior for each endpoint under various conditions. This makes it easier for new developers to understand the codebase and contribute effectively.  

Think of unit tests as clear instructions for maintaining your machine – they ensure everyone working on it understands how it functions.

Apidog - Create Automated Tests in Predetermined Environments

An API tool suitable for developers who wish to increase their efficiency is Apidog, an all-in-one API development tool that facilitates multi-stage testing cases called testing scenarios.

apidog specifications

Aside from rigorous testing, you can also create and modify new or existing APIs. The only thing that stops you from doing it is yourself!

Individual API Request Testing Using Apidog

With Apidog, you can test API endpoints individually. This can be preliminary tests that you can run before diving deeper with API unit testing methods. However, before you make the requests, you might have to read the API endpoint documentation to ensure that you know what to expect from the API.

To target the correct API endpoint, you first have to insert the corresponding API endpoint that you want to test. Once you have included the intended API URL, include the parameters that you want to use for the endpoint (if relevant).

In case you are unfamiliar with passing multiple parameters in an API URL, check out this article to find out how you can specifically target a resource inside a rich collection of data!

Tutorial: How to Pass Multiple Parameters in REST API URLs?
Two commonly seen parameter types are widely used in modern websites. Although they slightly differ based on their functions, parameters help developers identify specific resources found within a collection or system.

Creating a Testing Scenario for Your API Using Apidog

Testing scenarios are a much more realistic feature that simulates real-world situations. With Apidog, you can simulate potential scenarios where users and APIs might face, and therefore understand their respective interactions.

initializing new test scenario apidog

Firstly, hit the Testing button, followed by the + New Test Scenario button.

add detail apidog test scenario

Apidog will prompt you to fill in the details for your new test scenario. Make sure to give it a proper name so its function is predictable.

add step new test scenario api apidog

Continue by adding a step (or many more steps) to your test scenarios by clicking on the Add Step section. You should be able to see the image below.

select import from api soap apidog

Select "Import from API" from the drop-down menu.

add soap api web service test case scenario apidog

Next, select all the APIs you would like to include in your test scenario. In the example above, the API called NumberConversionSOAP has been included.

edit testing environment start run test scenario apidog

Before hitting the Run button to start your test scenario, make sure to change the test scenario environment, which should be Testing Env, as pointed out by Arrow 1.

apidog testing results

Once the testing scenario is complete, you are returned a condensed, rich analysis of your API's performance. You can see how much time is consumed, along with other factors that you may see significant in your API. Leverage the details of your API performance to compete with your competitors!

Conclusion

API unit testing serves as a critical cornerstone for building robust and reliable software. By isolating and testing individual API functionalities, developers can identify and fix bugs early in the development cycle, preventing them from cascading into larger issues later. This focus on granular testing fosters a more maintainable codebase, simplifies future modifications, and ultimately leads to a more positive user experience by ensuring APIs function as intended.

Furthermore, a well-established suite of unit tests acts as a safety net during the development process. As code evolves, unit tests provide a regression check, guaranteeing that changes haven't unintentionally broken existing functionalities. This not only saves development time but also instills confidence in the overall stability of the API. By investing in thorough API unit testing, developers can deliver high-quality APIs that empower seamless integration and foster a foundation for long-term success.

If you wish to find an API tool that can facilitate your API testing requirements, you should consider choosing Apidog - epsecially if you anticipate developing more APIs of your own or with your team. With Apidog, you can collaborate online with other developers in creating the API of your imagination.

Apidog An integrated platform for API design, debugging, development, mock, and testing
REAL API Design-first Development Platform. Design. Debug. Test. Document. Mock. Build APIs Faster & Together.
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