Testing, Quality Control and Quality Assurance

Testing is often confused with the processes of quality control and quality assurance. Testing is the process of creating, implementing and evaluating tests. If you are shopping for a new television, you can call that process "testing for the best TV for you"... it's kind of pretentious, but that is what you're doing as you compare prices and features to find what will work best for you. Testing usually has a limited scope and duration – you're just looking at TVs, and only in your town, you're not going to spend a year shopping, are you?

Testing is predicated on the use of a standard of quality: you have a specification of what's allowable (no broken links? ALT tags have values? maximum page weight is 10K?) and you compare the site to the standard, noting deviations and shortcomings. This seems simple, but your testing is only valuable if your standard of quality is comprehensive, well thought-out, and reasonable. If your standard has holes, then your testing process has blind spots.

Quality control is a refinement of testing, involving the formal and systematic use of testing and a precise definition of what quality means for the purposes of the test. You aren't just testing, you are testing and then doing something with the results. Quality control is used for testing a product or output of a process, with the test measuring the subject's ability to meet a certain benchmark or threshold of quality. The tests usually take the form of "does this product meet requirement X?", and are often pass-fail.

Effective quality control testing requires some basic goals and understanding:

You must understand what you are testing; if you're testing a specific functionality, you must know how it's supposed to work, how the protocols behave, etc.
You should have a definition of what success and failure are. In other words, is close enough good enough?
You should have a good idea of a methodology for the test, the more formal a plan the better; you should design testcases.
You must understand the limits inherent in the tests themselves.
You must have a consistent schedule for testing; performing a specific set of tests at appropriate points in the process is more important than running the tests at a specific time.
Any true attempt at quality control requires a great deal of planning before any tests are ever applied, and extensive documentation of quality standards, test plans, test scenarios, test cases, test results -- anything that goes into the testing must be carefully tracked and written down. In fact, for companies that manufacture products, as well as for software companies, a series of formal accreditation programs exist to measure and certify the company's adherence to some very strict standards, for example the ISO 9000 series of rules. No such certification systems exist for web sites, perhaps because sites are more experiences and resources than products to buy.

The distinctions between testing and quality control are important for an understanding of the roles and purposes of testing, but they are especially important to anyone involved in testing or creating large a web site. Based on my own experiences, I strongly recommend that testing for site quality be a priority for anyone who

works as part of a team that is building and/or maintaining a big web site, and whose responsibility is for testing, quality control, or quality assurance
delivers a site to a customer
receives site code from a contractor, agency, or technology partner
Testing -- and by extension quality control -- is reactive; that is, you test to find deviations from a standard. If you systematically employ a formal battery of tests on a consistent schedule, you will be able to pass a product with fairly stable quality. The shortcoming here is that this kind of testing does nothing to improve the quality of output; as far as user-experience is concerned, you're just running in place. Testing and quality control do nothing to raise the level of quality beyond perhaps tweaking the standard to "raise the bar". Quality assurance goes beyond quality control to examine the processes that create and shape the product: quality assurance looks at the quality of output, as well as at the quality of the inputs.