Best API Testing Frameworks and Tools: Features and Approaches Overview

What is API Testing?

First of all, it’s a crucial component quality assurance process and an integral part of any software development lifecycle that aims to detect bugs and improve code quality in the early stages. An API itself or Application Programming Interface is a collection of functions through which other software applications can be accessed.

API testing is a process of checking whether the software meets performance, functionality, security, and reliability. Validating the accuracy of data, HTTP status codes, and error codes. Also, among the benefits of test automation is that it identifies bugs, security vulnerabilities, and inconsistencies before it goes to UI and saves your team from spending extra expense, time, and effort on manual regression testing. Failure to test an API may lead to inefficient software.

The types of testing that you perform for an API testing are

• Functionality: Does the API work?
• Load: Does it load appropriately?
• Reliability: Can users connect to the API and achieve results?
• Usability: Is it easy to work with?
• Security Testing: How well data is encrypted?
• API documentation: how to guide a user into the purpose of the API

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API in the Three-Tier Architecture

APIs are a crucial component of a three-tier architecture as they facilitate communication and interaction between different layers of the software system. They provide a well-defined interface for clients (client layer) to access and utilize the functionality and data stored in the application (server layer) and data (data layer) tiers.

This separation of concerns and abstraction of functionality makes it easier to develop, maintain, and scale complex software systems.

API Testing Advantages

API testing offers several benefits for software engineering and quality assurance processes:

• Early issue detection. Since APIs get tested before the user interface is developed, it helps identify problems before they spread to other application parts.
• Quicker release. API testing helps speed up the software development lifecycle by allowing you to validate core functionalities and integrations early in the engineering process.
• Reduced testing costs. You can significantly reduce testing costs by catching defects earlier in the long run.
• Isolation of functionalities. API testing enables the focus on specific features and ensures they work correctly in isolation before integrating them into the system.
• Efficient data validation. Testers can verify data inputs and outputs, ensuring the API behaves as expected when transferring information.
• Better test coverage. API testing extensively covers your application’s functionality by focusing on the underlying logic and data exchange between components.

Types of API Testing

QA engineers take a multifaceted approach to API testing. They assess its performance by verifying if it provides accurate outputs and evaluating its compatibility with client-layer software. Additionally, testers examine how the API responds to exceptional scenarios, such as failures, unforeseen inputs, and extreme conditions, as well as potential security threats.

Let’s delve into each of these facets.

Functional Testing

Functional testing involves evaluating distinct functions within the codebase to ensure the API operates as intended within specified criteria. This can include:

• Load testing. It involves simulating many concurrent users or requests to measure the API’s response time and ability to handle a high load without degrading performance.
• Soak testing. Soak testing aims to evaluate how a system performs when subjected to a sustained or prolonged workload over an extended period. It helps uncover issues that may not surface during shorter performance tests.
• Stress testing. Stress testing pushes the API to its limits and beyond. It aims to identify the breaking point at which the API starts to fail or experience performance degradation. As a result, you uncover vulnerabilities and bottlenecks in the system.
• Spike testing. Spike testing assesses how a system handles sudden, sharp increases in user load or traffic. It is crucial for apps that may experience sudden surges in user activity, such as e-commerce websites during flash sales.
• Scalability testing. It checks how well the API can scale to accommodate increased user loads. This is crucial for solutions that need to handle a growing user base without a significant drop in performance.

One functional testing approach is Positive/Negative testing. Negative testing assesses an API’s responses to various incorrect inputs, while positive testing validates the API’s proper operation when the input adheres to established norms.

Performance Testing

API performance testing helps ensure the API can handle the expected load and deliver a seamless user experience. It consists of:

• Load testing. It involves simulating many concurrent users or requests to measure the API’s response time and ability to handle a high load without degrading performance.
• Soak testing. Soak testing aims to evaluate how a system performs when subjected to a sustained or prolonged workload over an extended period. It helps uncover issues that may not surface during shorter performance tests.
• Stress testing. Stress testing pushes the API to its limits and beyond. It aims to identify the breaking point at which the API starts to fail or experience performance degradation. As a result, you uncover vulnerabilities and bottlenecks in the system.
• Spike testing. Spike testing assesses how a system handles sudden, sharp increases in user load or traffic. It is crucial for apps that may experience sudden surges in user activity, such as e-commerce websites during flash sales.
• Scalability testing. It checks how well the API can scale to accommodate increased user loads. This is crucial for solutions that need to handle a growing user base without a significant drop in performance.

Security Testing

API security testing focuses on identifying vulnerabilities and weaknesses in an application’s API. It includes:

• Security testing. Security testing aims to identify vulnerabilities in an API that malicious actors could exploit. The primary goal is to protect the API against various threats and unauthorized access.
• Penetration testing. It focuses on simulating real-world attacks on an API to uncover weaknesses. This testing goes beyond identifying issues and aims to determine their impact.
• Fuzz testing. Fuzzing involves sending large volumes of random or unexpected data (fuzz) as inputs to identify vulnerabilities related to input validation and error handling.

Integration and Reliability Testing

API integration and reliability testing are essential to guarantee that an application’s API operates seamlessly and consistently in the production environment.

• Integration testing. It validates that the API interacts effectively and accurately with other system components, services, databases, or third-party APIs it needs to integrate. It is essential for complex applications with multiple interconnected modules, microservices architectures, or systems with intensive data exchange.
• Reliability testing. This testing focuses on assessing an API’s stability, availability, and fault tolerance under different conditions. It ensures that the API remains reliable even in adverse scenarios.

5 Things You Should Consider Before Selecting an API Testing Tool

There are lots of API testing tools available on the market, so it’s a challenge to pick the one. Here are a few tips from our experts on features you have to pay attention to:

Ease of Use and Key Capabilities

Your API testing tools should prioritize user-friendliness and deliver ample functionality to perform intricate tasks without the need for scripts. This allows even novice users to quickly adopt them with minimal training.

We recommend considering these essential capabilities:

• An intuitive, script-free, and visually guided approach to testing
• A framework for custom extensions
• Automation of assertions and validations
• Support for data-driven testing, where test cases are executed with various datasets
• Tools should facilitate the creation of reusable test components
• The ability to swiftly create tests, even before the service launch
• Authentication features should be included

Efficient Workflows

Your API testing tool should encompass advanced techniques that simplify tasks such as test generation, message flow analysis, data manipulation, and seamless integration of your API testing solution.

Here are several workflows your API testing tool should encompass:

• Thorough testing of logic flows within your API
• Leveraging artificial intelligence to assist in creating tests
• Simplifying the management and generation of test data
• Facilitating the observation and tracking of events
• Integrating Behavior-Driven Development (BDD) practices using tools like Cucumber

Supported Technologies

Any tool you choose must support the full range of required formats and industry-specific message protocols. For example:

• Comprehensive testing of REST APIs
• SOAP APIs evaluation
• Testing involving MQ (Message Queue) and JMS (Java Messaging Service)
• Adaptability to microservices architecture and the Internet of Things (IoT)
• Supporting database testing
• Testing on cloud-based applications and services
• Robust performance evaluation capabilities

Automation

Leveraging automation allows you to effortlessly incorporate your test cases into your nightly processes or trigger them as required. Pay attention to:

• Integration of your API testing into your Continuous Integration (CI) pipelines
• The ability to create custom system plugins
• Effortless execution of tests from the command line interface
• DevOps principles with incorporating open APIs into your API testing solution.

Maintenance and Management

Maintaining and managing an extensive repository of test cases can become a significant undertaking as your library expands over time. This includes:

• Test case visibility with identification of available API tests and the specific requirements associated with these tests
• The ability to organize your test case library into logical configurations
• Detailed test result reports with insights into the API quality and performance
• Change management feature, allowing to version different API test projects and understand how alterations to your applications impact them.
• Checking the total cost of ownership (TCO), including integration with requirements management systems, reporting options, test orchestration, adaptation to change, and accessibility.

Web API Testing Tools: How to Choose the One

There are lots of API testing tools available on the market, so it’s a challenge to pick the one. Here are a few tips from our experts on features you have to pay attention to:

• Easy-to-use, rich interface
• Integration with a constant integration pipeline
• Ability to organize group API requests into collections
• Possibility to run asynchronous tests to improve the execution time
• Synchronization options for teams
• Ability to generate API reports directly from the platform

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The Best API Testing Tools on the Market

To make the automation testing process efficient, it is important to use the best API testing platforms available for your project. Let’s review a few of them.

Postman

Being initially a Google Chrome plugin, now Postman is a cross-platform service that can be used as a web version as well as a desktop app either on Mac or Windows. It is easy to set up parameters on method calls. Here you can create automated tests, perform debugging, monitor the API, and manage requests. (But bear in mind that you can’t test more than one API simultaneously) Postman includes built-in tools and collections and supports several formats, including Swagger and RAML.

The service is a free-to-use API testing tool, but extra features cost $12 for each user per month.

SoapUI

SoapUI is also among the top REST API test tools. The service offers free and fixed packages. The first one provides users with the full source code, other features include load tests for functional test cases and the capacity to reuse security scans. The fixed package offers additional features:

• Asynchronous testing
• Data-driven testing
• Tests on GraphQL, REST, JDBC, SOAP, JMS, and other web services
• Integrated API security testing
• Seamless integration with the js frameworks
• Extensive language support (Python, Java, etc.)

Apigee

It is a cross-cloud platform, powered by JavaScript, that enables the measuring and testing of API performance. It includes the following features:

• Tracking API traffic, error rates, and response times to identify performance issues
• Ability to create API proxies and their deployment in the cloud
• Adaptation with APIs containing data

Apigee allows a trial period for users to try its features. Then you can choose a package that satisfies your needs.

Karate DSL

Karate DSL combines API test-automation, performance-testing, mocks, and UI automation. It helps users get on with API testing quickly by allowing them to create scenarios for API-based BDD tests and perform them with no need to write down step definitions. Karate DSL is one of the open-source API testing tools which means that you can use it for free, but the solution costs depend on the requirements.

API Fortress

Among other API testing platforms, we’ve decided to highlight API Fortress as it is a great monitoring tool for REST, SOAP, GraphQL, Web Services, and Microservices. It also offers simple test integration and facilitates the automation of performance and functional testing. The price of API Fortress depends on specific project needs.

Testim

Testim is the platform for the functional, load, and security testing of SOAP REST, GraphQL, and other web services. It employs AI to help with test suite execution, maintenance, and even creation. One of the cool features here is a framework that learns with each test maintenance activity and suite execution Testim works by a freemium model, and different plans designed to fit your team.

Hopscotch

Hopscotch is an open-source API testing tool with a minimalistic user interface. A platform makes testing easier by offering a standard package of features. Some of them include the possibility of creating collections for storing API requests, REST, GraphQL, SOAP, JMS, and JDBC testing, sending and receiving data with a SocketIO server, etc. You can use it for free.

Why conduct performance testing? Check what we have to say about it!

API testing frameworks

Some of the tools we’ve listed above are better for writing an automation framework while others can be used as they are. Here are a few reasons to consider writing your own framework to test API. It’s:

• Customizable
• Gives you more flexibility in managing your test data
• Avoids any type of limitations of a ready-made tool
• Allows you to add any specific features and libraries that you need
• Takes away the question of cost

In any way, remember that it’s important when hiring QA engineers to involve them in the project from the very beginning.

Consider Inoxoft Your Trusted Partner

Inoxoft is a company providing custom software development services and creating industry-specific software to satisfy your business needs Take advantage of our QA automation testing services and get

• Team of certified QA engineers
• Stable code and great performance
• Cost-effectiveness
• Risk elimination
• Efficiency and Accuracy
• On-time Delivery

Final Thoughts

In this article, we have covered basic information about API testing, and API testing tools. We know that it is difficult to choose as there is no one perfect tool for everyone.

Some may find the features of the commercial platforms sufficient but their price is pretty high. Open-source tools are more affordable but require experience and effort to implement the right frameworks. A perfect match between the API testing tool and the project’s specific requirements will simplify the process for the whole team and more importantly, it will make the software even more efficient.

Need to transfer your data safely? Consider data migration methodology!