Software Quality Assurance (‘SQA’ or ‘QA’) intend to improve all activities associated with software development, from requirements gathering, design and reviews to coding, testing and implementation. It involves the entire software development process – monitoring and improving the process, making sure that any agreed-upon standards and procedures are followed, and ensuring that problems are found and dealt with, at the earliest possible stage. Unlike testing, which is mainly a ‘detection’ process, QA is ‘preventative’ in that it aims to ensure quality in the methods & processes – and therefore reduce the prevalence of errors in the software.

A rigorous SQA plan carried out scrupulously by seasoned QA professionals will confer certain benefits:

1. Improved customer satisfaction
2. Reduced cost of development
3. Reduced cost of maintenance

Quality starts and ends with documentation, if you have no documentation, then you can have no quality. We write down what is supposed to happen. Then we write down what actually happens. Software that contains few faults is considered by some to have higher quality than software that contains many faults.

Quality software is reasonably bug-free, delivered on time and within budget, meets requirements and/or expectations, and is maintainable. However, quality is a subjective term. It will depend on who the customer is and their overall influence in the scheme of things. Each type of customer will have their own view on quality; the accounting department might define quality in terms of profits while an end-user might define quality as user-friendly and bug-free.

Software bugs will almost always exist in any software module with moderate size: not because programmers are careless or irresponsible, but because the complexity of software is generally and design defects can never be completely ruled out.

Discovering the design defects in software is equally difficult, for the same reason of complexity. Because software and any digital systems are not continuous, testing boundary values are not sufficient to guarantee correctness. All the possible values need to be tested and verified, but complete testing is infeasible.

1. Verify the software behaviour
Verification is the checking or testing of items, including software, for conformance and consistency by evaluating the results against pre-specified requirements. [Verification: Are we building the system right?]

2. Detect errors
Testing should intentionally attempt to make things go wrong to determine if things happen when they shouldn't or things don't happen when they should.

3. Validate software is what user wanted.
Validation is the process of checking that what has been specified is what the user actually wanted.

Software bugs will almost always exist in any software module with moderate size: not because programmers are careless or irresponsible, but because the complexity of software is generally intractable.

Most of the defects in software are design errors, not manufacturing defects. Testing is more than just debugging. The purpose of testing can be quality assurance, verification and validation, or reliability estimation. Testing can be used as a generic metric as well.

The purpose of testing is verification, validation and error detection in order to find problems – and the purpose of finding those problems is to get them fixed.