Software is a very sensitive domain. If a single bit of a 100MB executable is wrong, the entire application can be brought to it's knees. Very few other domains suffer such extreme sensitivity to error. But one very important domain does: Accounting. A single digit error in a massive pile of spreadsheets and financial statements, can cost millions, and bankrupt an organization.
Accountants solved this problem long ago. They use a set of practices and disciplines that reduce the probability that errors can go undetected. One of these practices is Dual Entry Bookkeeping. Every transaction is entered twice; once in the credit books, and once in the debit books. The two entries participate in very different calculations but eventually result in a final result of zero. That zero means that the all the entries balance. The strong implication is that there are no single digit errors. [...]
We in software have a similar mechanism that provides a first line of defense: Test Driven Development (TDD). Every intention is entered in two places: once in a unit test, and once in the production code. These two entries follow very different pathways, but eventually sum to a green bar. That green bar means that the two intents balance, i.e. the production code agrees with the tests. This is not perfect, and other controls are necessary; but there can be little doubt that TDD vastly decreases the defect load in software projects. [...]
Previous Topic
