Everything You Need to Know About Unit Testing

Everything You Need to Know About Unit Testing

What are APIs?

An API is a set of protocols and tools for building software applications. It specifies how software components should interact with each other, allowing them to communicate and exchange data. APIs often expose data and functionality through a set of endpoints, which are URLs that accept requests and return responses.

Why use APIs?

There are many reasons to use APIs in your own projects. Here are a few examples:

  • Accessing data from other sources: APIs can allow you to access data from other websites, databases, or services. For example, you might use an API to retrieve data from a social media platform, a weather service, or a financial market.

  • Integrating with other systems: APIs can allow you to integrate your own projects with other systems, such as payment processors, shipping carriers, or CRM systems.

  • Extending your own functionality: You can use APIs to add new features or functionality to your own projects. For example, you might use an API to add image recognition or translation capabilities to your app.

How to use APIs in your own projects

Using APIs in your own projects typically involves making HTTP requests to the API's endpoints. Depending on the API, these requests might be GET requests to retrieve data, POST requests to send data or other types of requests to perform different actions.

Here's an example of how to make a GET request to an API using Python:

import requests

import requests
response = requests.get("https://api.example.com/endpoint") 
if response.status_code == 200:
   data = response.json()

This code uses the requests library to make a GET request to the specified endpoint. If the request is successful (i.e. the API returns a status code of 200), it will print the data returned by the API, which is typically in the form of a JSON object.

Depending on the API you are using, you may need to provide additional information in the request, such as an API key or other authentication credentials. You can also use different HTTP verbs (e.g. POST, PUT, DELETE) to perform different actions.

Types of API Testing

  • Unit Testing: testing manually one endpoint by one call, waiting for one response.

  • Functional Testing: testing functions based on the code.

  • User Interface Testing: testing how easy it is to use and access the application.

  • Security Testing: to make sure of the application’s safety against threats.

  • Load Testing: testing the ability to withstand heavy load.

  • Runtime & Error Detection: to make sure it’s empty from errors.

  • Validation Testing: verifying the final efficiency, behavior, and other functions.

  • Fuzz Testing: to rule out any possible negative behaviors.

  • Integration Testing: It’s the most common API testing type.

  • End-to-End Testing: in order to verify the data influx through some API connections.

Unit Testing

Unit testing is a software testing technique that involves testing individual units or components of an application in isolation from the rest of the application. The goal of unit testing is to validate that each unit of the application is working as intended and meets the specified requirements.

Unit tests are typically written by developers as they write code, and they are run every time the code is modified to ensure that the changes have not introduced any new bugs or caused any existing functionality to break.

Benefits of Unit Testing

There are several benefits to unit testing:

  1. Early Detection of Bugs: Unit tests can identify problems with code early on, before the code is integrated into the larger application. This can save time and effort in the long run, as it is easier to fix bugs when they are isolated to a specific unit or component.

  2. Improved Code Quality: Writing unit tests forces developers to think about how their code will be used and to consider edge cases that might not have been initially considered. This can lead to better code design and higher overall code quality.

  3. Easier Maintenance: As code evolves and changes over time, unit tests can provide a safety net to ensure that changes do not break existing functionality. This can make it easier to maintain and update the codebase.

  4. Increased Confidence: By running unit tests regularly, developers can have confidence that their code is working as intended and is ready for integration and testing at the next stage of the development process.

Best Practices for Unit Testing

To write effective unit tests, it is important to follow some best practices:

  1. Keep unit tests simple and focused: Each unit test should test one specific aspect of the code and should not have any external dependencies.

  2. Use test-driven development: Write the unit test before writing the code, so that you have a clear understanding of what the code needs to do.

  3. Use assertions: Assertions allow you to verify that the code is doing what it is supposed to be doing.

  4. Use mocking: Mocking allows you to isolate the unit under test and simulate external dependencies.

  5. Use a testing framework: There are many testing frameworks available for different programming languages, such as JUnit for Java and NUnit for .NET. These frameworks provide helpful tools and features for writing and running unit tests.

  6. Use a code coverage tool: Code coverage tools measure how much of the code is being tested by the unit tests. This can help identify areas of the code that are not being adequately tested and help ensure that all aspects of the code are being covered by unit tests.

  7. Write meaningful test names: Test names should clearly describe what the test is testing and should be easy to understand.

  8. Follow a testing workflow: It is a good idea to follow a testing workflow, such as the "Arrange-Act-Assert" pattern, to help ensure that unit tests are structured and easy to understand.

API Testing Tools

API testing is an important part of the software development process, as it helps to ensure that an API functions correctly and meets the needs of its users. There are a wide variety of tools available for API testing.


Keploy is an e2e testing toolkit for developers that generates tests cases and data mocks.

It converts API calls into test cases.

Mocks/stubs are automatically generated with the actual request/responses.

Keploy Features

  1. API calls from anywhere can be converted to Test-Case.

  2. Mutations are mocked automatically.

  3. Accurate Noise Detection

  4. Native interoperability

  5. Simple Integration Framework for New Libraries

Get your hands dirty with Keploy here.

You can also star them on GitHub, I am sure they won't mind 😝.


Postman is a API testing tool that provides a graphical user interface (GUI) for making and analyzing API requests.


SoapUI is an API testing tool that is specifically designed for testing APIs that use the Simple Object Access Protocol (SOAP).


Unit testing is a valuable tool for ensuring the quality and reliability of software. In this blog post, we've explored some of the most popular Unit testing tools (tool for a tool), including Keploy, Postman, SoapUI. These tools offer a range of capabilities for testing APIs, including unit testing, functional testing, security testing, performance testing, and more. By using the right API testing tool for your needs, you can ensure that your APIs are reliable, performant, and secure.

I hope you now have a thorough understanding of the API and Unit Testing.

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