What Is Unit Testing? 15 Automated Unit Testing Tools

Software development is a creative endeavor, but it can be filled with tedious tasks. Most mundane of all is writing “unit tests,” bits of code to verify that software components work as intended. Unit tests help developers catch bugs early and ensure that code can be maintained.

Ideally, developers writing code for a program write unit tests as they go along. But writing unit tests is the drudge work of software development and it can take up a significant amount of a developer’s time. Worse, developers can make mistakes in manually written tests for complex codebases. Consequently, a lot of software lacks adequate unit tests and that makes the code difficult to maintain. Without unit tests, if something breaks, finding the problem can be like hunting for a needle in a haystack.

What Is Unit Testing?

A unit is a part of a program that performs a particular operation. Units are the building blocks of software; a piece of software is a stack of units. If a unit doesn’t do what it’s supposed to do, the software program will not work efficiently — or, in some cases, will not work at all.

Unit testing involves testing individual units of a software application in isolation to ensure they function as expected. The process involves identifying the unit to be tested, writing a test case that exercises the unit and verifies its behavior, running the test and observing the results. If the test fails, the developer investigates the issue, makes necessary changes to the unit’s code, and re-runs the test until it passes. Unit testing helps catch bugs early, improves code quality and enables faster debugging, ultimately ensuring the reliability and quality of the software application.

Automated unit testing will play an increasingly critical role in maintaining the integrity and robustness of the code that runs much of our lives. Artificial intelligence is now helping developers write those unit tests, freeing them to focus on higher-value tasks.

What Are Unit Testing Examples?

One of the most promising tools is Diffblue Cover, an AI-powered platform that automatically writes unit tests for Java code, one of the most popular programming languages. Diffblue uses reinforcement learning to analyze the codebase and generate human-readable, executable tests that cover a wide range of scenarios. “We only focus on unit tests,” said Peter Schrammel, Diffblue’s co-founder, explaining his company’s success in solving the problem for Java.

Another notable tool is EvoSuite, an open-source framework that uses genetic algorithms to generate test suites for Java programs, although EvoSuite’s generated tests are not as readable as those produced by Diffblue.

Both Diffblue and EvoSuite stand out for being completely automatic.

Beyond that, there are many code suggestion tools that can help developers write tests. While these tools speed up the work of writing unit tests, they are not fully automatic and still require a developer’s time and attention.

For example, Amazon CodeWhisperer, GitHub Copilot, and even ChatGPT can look at a function and predict a unit test. But generative AI based on large language models (LLMs) is prone to errors, and so developers still need to check their work. They help developers, but don’t free them from the unit-test writing task.

The space is starting to heat up with new start-ups entering the race. Startup Cognition has announced an AI agent called Devin that it claims can scan code, identify and fix bugs and write unit tests. A Cognition engineer named Andrew posted a video on YouTube of Devin reviewing a code repository and successfully writing a regression test on its own. Devin is not yet publicly available so it will take some time to see if it can challenge the current leaders.

Top Automated Unit Testing Softwares And Tools

Here are the top tools on the market today for writing unit tests. These tools use various AI techniques to automate and optimize different aspects of code review, test generation and quality assurance.

DiffBlue Cover

DiffBlue Cover provides AI-powered unit test generation for Java codebases.

• Automated Java unit test generation tool
• Uses reinforcement learning to generate and optimize tests
• Integrates with popular Java integrated development environments (IDEs) and build tools
• Achieves high code coverage and maintains tests over time
• Offers both cloud and on-premises deployment options

GitHub Copilot

GitHub Copilot is powered by generative AI models developed by GitHub, OpenAI and Microsoft, and is trained on all natural languages that appear in public repositories.

• AI pair programmer that suggests code and entire functions in real-time
• Supported in terminals through GitHub CLI (command line interface) and natively integrated into GitHub.com with the GitHub Copilot Enterprise plan
• Suggests code completions in the code editor
• Answers questions in a chat
• Automatically pulls relevant context from the opened project

Tabnine

Tabnine is an AI coding assistent supporting multiple languages and IDEs.

• AI coding assistant; supporting code generation, explanation, and fixes across 80+ languages and frameworks, plus support for automatic generation of tests and documentation.
• Support for a broad set of IDEs, including all of the most popular (eg., Visual Studio, VSCode, IntelliJ, Eclipse, Android Studio)
• Pulls context automatically from all relevant files accessible from the IDE, and can be connected to any Git-based repo for increased context.
• Offers a proprietary model trained exclusively on permissive code, and also offers custom models trained on additional customer’s code (trained and deployed privately)
• Offers deployment in secure SaaS, or private deployments on VPC or on-premises (can be fully air-gapped)

CodiumAI Codiumate

CodiumAI Codiumate is an AI coding assistant for writing, reviewing and testing code.

• IDE plugin for interactive high-quality code generation, testing and reviewing
• Interactively generates a task plan and spec
• Suggests task-aware code completions in the code editor
• Answers questions in a chat
• Automatically pulls relevant context from the opened project
• Provides guidance, code improvements, task review, etc. to generate high-quality code to complete the task
• Private instances can be installed on-premises
• Uses a proprietary model (but enterprises can choose to use OpenAI models instead)

Google Cloud’s Duet

Google Cloud’s Duet provides AI-powered code completion and generation for developers

• Chat interface for coding questions and guidance on cloud best practices
• Code explanation to quickly understand, map and navigate unfamiliar code bases
• Code security guardrails to scan AI-generated code for vulnerabilities
• Leverages Google AI foundation models
• Source citations to help comply with license requirements

Amazon Q/Amazon Codewhisperer

Amazon Q/Amazon Codewhisperer is an AI-powered coding companion from Amazon Web Services.

• Accessible directly in popular IDEs
• Proposes code snippets to full functions, across 15 programming languages
• Provides company-specific responses through customization capability
• Scans for security vulnerabilities and suggests remediation in code
• Filters out code suggestions that may be considered biased or unfair
• Flags code suggestions that may resemble particular open-source training data
• Upgrades programming language versions
• Answers questions in a chat
• Builds new application features with a descriptive prompt
• Automatically pulls relevant context from the opened project
• Uses a proprietary model

Symflower

Symflower provides automated unit test generation for Java.

• Combines symbolic execution, static analysis, and natural language processing
• Generates readable, maintainable, and effective unit tests
• Explains test assertions and edge cases in natural language
• Integrates with Java IDEs and continuous integration/continuous delivery (CI/CD) pipelines

Testim

Testim is an AI-based test automation platform for web and mobile apps.

• AI-powered test automation platform
• Supports web, mobile and API testing
• Uses machine learning to create and maintain tests
• Provides visual test editing and debugging tools
• Integrates with popular CI/CD tools and test management systems

Squaretest

Squaretest is a plugin for IntelliJ IDEA that automatically generates unit tests for Java classes.

• Uses dataflow analysis, control flow analysis, pattern detection and heuristics to generate as much of the tests as it can. Manual work is required to complete the generated tests.
• Enables developers to customize output by creating custom Apache Velocity templates.
• Enables developers to choose which dependencies should be mocked, which methods should be tested and how to construct the source class.

Bito

Bito is an AI-powered code review and quality assurance tool.

• Analyzes code changes and understands your codebase, providing real-time feedback
• Identifies potential bugs, security issues and performance bottlenecks
• Supports multiple programming languages and frameworks
• Integrates with popular version control systems and CI/CD tools

DeepUnitAI

DeepUnitAI is an AI tool that writes unit tests for multiple programming langauges.

• AI-driven unit test generation tool
• Supports vrious langauges including Typescript, Javascript, Java, Python and C#
• Uses deep learning to understand code semantics and generate meaningful tests
• Provides IDE extensions, CI/CD pipelines and CLI option.

Seniordev.ai

Seniordev.ai is an AI programming assistant for code generation, optimization and mentoring.

• Web-based application designed to enable dev teams to work more efficiently and effectively
• Uses AI to review pull requests, create/update docs and generate unit tests where applicable
• Supports multiple programming languages and frameworks
• Provides a collaborative interface for team members to work together
• Integrates with popular version control systems and project management tools

Testsigma.com

Testsigma.com is an AI-driven, codeless test automation platform for web and mobile.

• AI-driven test automation platform for web, mobile and API testing
• Supports codeless test creation using natural language processing
• Provides a visual interface for creating and managing tests
• Offers real-time test results and analytics
• Integrates with popular CI/CD tools and test management systems

Functionize

Functionize is an intelligent test automation platform that uses machine learning.

• AI-powered test automation platform for web and mobile applications
• Uses natural language processing and machine learning to create and maintain tests
• Supports cross-browser and cross-device testing
• Provides a visual interface for creating and managing tests
• Integrates with popular CI/CD tools and test management systems

Mabl

Mabl is an AI-powered, codeless test automation platform for web applications.

• Built using cloud, AI and low-code innovations
• Functional and non-functional testing scalability across web apps, mobile apps, APIs, performance and accessibility testing
• Delivers 3x faster test creation, 70% maintenance reduction, 10x faster test runs, 80% savings over homegrown solutions
• Integrations with Slack, Jira, Microsoft Teams and Github

Bottom Line

As the field of AI-assisted development continues to evolve, we can expect to see more sophisticated automated unit testing tools that leverage advanced machine learning techniques to generate even more comprehensive and reliable test suites. These tools will likely integrate seamlessly with development workflows, making it easier for developers to incorporate automated testing into their daily routines.