Software testing practices ensure quality assurance by systematically identifying and addressing defects in software before its release. These practices encompass various methodologies like unit testing, integration testing, and user acceptance testing, each aimed at verifying different aspects of the software's functionality. By employing automated testing tools and manual testing techniques, developers can evaluate performance, reliability, and user experience, thus mitigating risk. Ensuring a thorough testing process leads to a more stable product, enhances customer satisfaction, and decreases long-term maintenance costs, ultimately contributing to the project's overall success.