Software Testing Engineering
(Computer Science)

One of the difficulties in thinking about software is its huge variety. A function definition in a spreadsheet cell is software. A smartphone app is software. The flight management system for an Airbus A380 is software. A word processor is software. We shouldn't expect a single discipline of software engineering to cover all of these, any more than we expect a single discipline of manufacturing to cover everything from the Airbus A380 to the production of chocolate bars, or a single discipline of social organization to cover everything from the United Nations to a kindergarten. Improvement in software engineering must come bottom-up, from intense specialized attention to particular products.

How can it be that we have so much software that is reliable enough for us to use it? The answer is simple; programming is a trial and error craft. People write programs without any expectation that they will be right the first time. They spend at least as much time testing them and correcting errors as they spent writing the initial program. Large concerns have separate groups of testers to do quality assurance. Programmers cannot be trusted to test their own programs adequately. Software is released for use, not when it is known to be correct, but when the rate of discovering new errors slows down to one that management considers acceptable. Users learn to expect errors and are often told how to avoid the bugs until the program is improved.

A key characteristic of the engineering culture is that the individual engineer’s commitment is to technical challenge rather than to a given company. There is no intrinsic loyalty to an employer as such. An employer is good only for providing the sandbox in which to play. If there is no challenge or if resources fail to be provided, the engineer will seek employment elsewhere. In the engineering culture, people, organization, and bureaucracy are constraints to be overcome. In the ideal organization everything is automated so that people cannot screw it up. There is a joke that says it all. A plant is being managed by one man and one dog. It is the job of the man to feed the dog, and it is the job of the dog to keep the man from touching the equipment. Or, as two Boeing engineers were overheard to say during a landing at Seattle, “What a waste it is to have those people in the cockpit when the plane could land itself perfectly well.” Just as there is no loyalty to an employer, there is no loyalty to the customer. As we will see later, if trade-offs had to be made between building the next generation of “fun” computers and meeting the needs of “dumb” customers who wanted turnkey products, the engineers at DEC always opted for technological advancement and paid attention only to those customers who provided a technical challenge.