We will perform testing whenever we need to check all requirements are executed correctly or not, and to make sure that we are delivering the right quality product.

The correct answer to the question “When do we perform testing?” is that testing is typically performed throughout the software development lifecycle. Testing is not a one-time activity but is integrated into different phases of the development process to ensure the quality of the software product.

The testing process can be broadly categorized into different stages, including:

Unit Testing: Developers perform unit testing to check individual components or functions of the software for correctness.
Integration Testing: Testing is done to ensure that different components or modules work together as expected when integrated.
System Testing: The entire system is tested to verify that it meets the specified requirements.
Acceptance Testing: The software is tested to ensure it meets the acceptance criteria and is ready for deployment.
Regression Testing: Testing is performed to ensure that new changes do not adversely affect existing functionality.
User Acceptance Testing (UAT): End-users may perform testing to ensure the software meets their needs and expectations.
Performance Testing: The software is tested for its performance under different conditions, such as load testing, stress testing, and scalability testing.
Security Testing: Testing is done to identify and address potential security vulnerabilities in the software.

In summary, testing is an ongoing process that starts from the early stages of development and continues throughout the software’s life cycle to identify and rectify defects and ensure the quality of the product.