Software Testing

We all know what testing is. We’ve been doing it for years, in and out of school. We took tests, and
teachers gave us marks and told us we were good, bad, or indifferent. People had got the idea that tests might be used to predict things about other people.
In 1904 a Frenchman called Alfred Binet was given the task of deciding whether or not children were subnormal. Monsieur Binet was a member of a committee of Eminent Frenchmen, each eager to propose his own Theory of Child Intelligence and How It can be Determined. M. Binet listened, extracted from each Eminent Frenchman a set of tests, added many of his own invention, and tried them out on sets of children. From the behavior of the children he decided which tests were useful. He then threw out those tests which failed to predict successfully, and tried again.

What did these tests prove? Nothing. They indicated the level of a child’s intelligence at the time the test was administered. They did not prove that the child has great ability or potential. They have been given to an enormous number of children. They are still in use today.

Mr. Cyril Burt was a psychologist interested in predicting the ability of children. The British government wanted to reduce the cost of education. They reached a position whereby Mr. Cyril Burt provided (much) questioned figures that “proved” that it was possible to predict a child’s ability, and the British government imposed a test on all British children at the age of 11 (called the 11-plus), which determined whether a child would go to a Grammar school (for the brighter) or a Secondary-Modern school (for the less-bright). Many studies have shown that the tests were very bad predictors of a child’s ability and have blighted the lives of a generation of children. Britain still has a terrible shortage of graduates and technicians, but Mr. Cyril Burt was knighted.

Conclusions

1. Theories can be disproved.
2. Theories can be very useful and good predictors within a limited range of environments.
3. Tests only work in a limited range of environments.
4. Conclusive tests are very difficult to write.
5. There is always someone who believes despite the evidence.
6. Test the tests before you use them.
7. Faking test results can be a way to social advancement — but destroys your reputation.