What technique is commonly used for software testing to ensure quality?

Unit testing is a fundamental technique in software testing that focuses on verifying the smallest parts of an application, usually individual functions or methods, to ensure they work as intended. By isolating these small units of code, developers can identify errors at an early stage of the development process, making it easier and less expensive to fix issues before the software is further integrated or deployed.

This technique emphasizes the importance of the internal correctness of components, ensuring each unit performs its specified task. This foundational step is critical for building reliable software, as it allows for ongoing verification after every change or addition to the codebase. It ultimately contributes to the overall quality of the software by ensuring that each component behaves as expected in isolation, which increases confidence when these units are later integrated into larger systems.

In contrast, other testing types like integration testing, regression testing, and acceptance testing, while also essential, focus on different aspects of the code, such as the interaction between components, verifying that new changes have not broken existing functionality, and ensuring the software meets business requirements, respectively. However, without effective unit testing, these other levels of testing may be jeopardized due to undetected flaws in the individual components.