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What Is Unit Testing?

Verify error-free code to meet coverage targets and comply with safety and security standards. In test-driven development (TDD) environments, code functionality, and quality remain intact with no regressions so there’s no need to worry about changes to existing code.

Why Is Unit Testing Important in Software Testing?

Is it considered a testing method or testing technique?

Unit testing is more than just a testing technique. It’s a testing method for exercising individual units of source code that provides an excellent way to demonstrate the correct software behavior. It’s the verification of module design that ensures each software unit does what it’s required to do.

Unit testing solutions are used in software development to ensure code safety, security, and reliability. By quickly building and auto-generating robust unit test cases, you can ensure code quality through the execution of test cases in any cross-platform, host, virtual, or hardware target environment.

Unit testing features include:

  • Multi-metric code average analysis (statement, line, branch, block, call, decision, single condition, and MC/DC)
  • A powerful stub and mock framework
  • Automated cross-platform execution

Unit testing is an integral part of software development. Automated testing tools, similar to those used in systems testing, are highly useful for developers and anyone who runs code. In embedded development environments, where hardware and software systems must work in sync and comply with exacting functional safety standards, unit testing is extremely useful.

The automated unit testing framework put in place will also transition into your regression test suites. This is critical later in the lifecycle as software updates, patches, or new requirements are implemented. For huge productivity gains, you can also automate unit and regression testing into your modern development CI/CD workflow.

Learn more about optimizing unit and regression testing with automation to save time and gain better coverage.


The Benefits of Unit Testing

Isolate the Code Under Test

Isolate the unit to be tested with an automated stubbing framework and mocks in cases where the dependent code is unavailable, cannot be easily controlled, or where fault injection is difficult.

Accommodate Code Changes

Features like change-based testing allow you to efficiently analyze code changes so you can quickly zero in on test cases that need to be modified for retesting.

Incorporate Unit Testing Into CI/CD Workflows

Integrate unit testing easily and quickly into your Agile or streamlined CI/CD pipeline with continuous testing that delivers high-quality software.

Automate Compliance of Safety and Security Critical Applications

Spend less time meeting industry requirements with unit test automation for safe, secure, and reliable code. Look for solutions that are TÜV SÜD certified for automotive standards ISO 26262, railway standards EN 50128, and functional safety IEC 61508 for all ASIL and SIL levels. Tool Qualification Kits for DO-178B/C are also good to look for.

Achieve 100% Structural Code Coverage

Unit testing tools help teams that develop enterprise and embedded applications by thoroughly testing code and achieving test passes and code coverage goals. For safety-critical development, unit testing tools account for all coverage types from statement and branch to MC/DC and object code.

Automated Unit Test Case Generation

Manual testing is tedious because creating unit tests manually is a long-drawn-out process. Automation helps with unit test creation. Configurable test case generation can build smart test cases to identify bugs, automate code coverage, collect results and metrics to feed project analytics.

AI-Infused Unit Testing Helps the Whole Team

With automated AI assistance, unit testing best practices are more approachable for the entire team. It gives novice unit testers a better understanding of what the test is doing. It helps expert unit testers save time and effort by creating meaningful tests - providing valid asserts that test the true functionality of the code.

Parasoft Unit Testing Tools for Development Environments

Give your software developers the right testing tools to increase productivity and speed to market. Parasoft’s suite of products for unit testing is available for every development environment. When you implement a Parasoft tool, you can be sure that your new code works as expected without negatively impacting the existing functionality.

Unit Testing Best Practices

Realize the best ROI from your unit tests with proven practices to test code. Programmers, whether beginners or experienced developers, can easily incorporate these best practices into data-driven testing to improve capabilities for testable production code.


Execute a daily, hourly, or continuous integration delivery process with automation for unit and regression testing. Provide each team member with review access for test fails and test passes reports


Implement an organized test practice to drive the success of tests at all levels. Provide your team with an organized approach to make the process scalable and sustainable for testing practices as well as tool usage and integration into current development pipelines.


When writing tests, it’s important to also be able to write them as application code because the two go hand-in-hand. This is also true for the code review process in test-driven development (TDD). Behavior-driven programming tests can be written before the application code.


Whenever you debug, you should have a verifiable test to be certain that the fix and debugging is in place permanently.

Zero-Tolerance Policy

Establish a zero-tolerance policy for test fails. Test fails indicate real issues and should be addressed immediately. Don’t pass them on to the software quality assurance team or worse, allow failures to integrate into the released product.


Refactor the tests as needed when the code changes. It’s important to maintain tests, especially if they fail. Tests lose value if they're not kept up to date when the application changes. Each test failure costs time and money to investigate.

How Do I Get Started With Unit Testing?

The best way to get started is to incorporate automated unit testing into your organization. Automated unit and regression testing deliver the largest impact on testing by substantially reducing, if not removing, error-prone, tedious manual work.

You’ll need an organized approach to drive success with testing at all levels and make the process scalable and sustainable. Teams need an organized approach for testing practices, tool usage, and integration into current development pipelines.

Also, make sure you establish a zero-tolerance policy for test fails because there’s no reason to run the tests if you’re not addressing issues, which you should do immediately. Maintain and update your tests so they don’t lose value.


Screen capture of Parasoft C/C++test test case showing line coverage.

Collecting and analyzing code coverage metrics is an important aspect of delivering software quality. Code coverage measures the completion of test cases and executed tests. It provides evidence that validation is complete as specified by the software design. It also demonstrates the absence of unintended behavior. Code that isn’t covered by any test is a liability because its behavior and functionality are unknown.

Why Parasoft?

Parasoft unit testing solutions automate test execution and data collection. Our solutions automatically create unit tests to save time and energy at test creation time. The technology sets up the unit test framework. It instantiates objects and configures mocks for appropriate objects and method calls used by the method under test.

With Parasoft, the mundane work is already done for developers. Not only do we provide unit test creation wizards, but we also provide content to complete the process. This sets our solutions apart from others.

Assertions must be manually defined. If mocking frameworks are used, a significant amount of manual coding is required. With Parasoft, real-time context-aware assistance in the developer’s IDE is provided. Automatic unit test creation quickly and efficiently completes the missing content from skeleton unit tests.

Get the most from your unit testing tool.

  • Create test framework, instantiates objects, and configures appropriate mock objects and methods.
  • Perform runtime analysis of test automation execution to highlight object values that changed during the test and recommend assertions for verification of these values.
  • Identify method calls that should be mocked to better isolate the test code.
  • Detect system resources created but not freed after test completion, potentially creating an unstable test environment.
  • Collect code coverage and other metrics.

Frequently Asked Questions

Developers and software testers can perform unit testing manually by executing unit test cases that exercise the code in development to ensure functional behavior is as defined by requirements. It also flushes out any defects and makes sure the code is robust enough to handle unexpected scenarios.

Unit testing can also be automated by testing tools that use a testing framework to develop and maintain test cases. Test automation is the more commonly used method.

Running unit tests is the isolation of pieces of code commonly referred to as functions, procedures, or methods for the purpose of ensuring that these units are robust, bug-free, and function as intended.

The units may have input values and expected output values, which testing with a range of min, mid, and max input values and outside boundaries values, including uninitialized pointers and other forms will help produce safe, secure, and reliable units of code.

Each unit of code, function, or procedure, for example, satisfies or helps satisfy a functional requirement. Unit testing validates the requirement through execution, but it also ensures that the unit is of high quality and bug-free.

Unit testing that is done early in the development process provides benefits like finding and fixing bugs and other issues early. It’s easier and less expensive to fix these issues early or before the software goes to market.

Application testing requires more than just unit testing. Unit testing is also referred to by some as white-box testing because the developer depends on the visibility into the details of the source code. Another type of testing is black-box testing in which the developer only cares about the functional results, but nothing about the internal workings of the code, interface, or API, which contrasts with white-box testing. Black-box testing can also be referred to as system testing, which is performed by the quality control testers. It’s referred to as acceptance testing if you are testing to make sure your customer requirements are being satisfied.