Design By Contract is a design technique developed by Bertrand Meyer and a central feature of the Eiffel language that he developed. Design By Contract is not specific to Eiffel, however, and is a valuable technique for any programming language. At the heart of design by contract is the assertion. An assertion is a Boolean statement. An assertion should never be false, and will only be false due to a bug. Typically assertions are only checked during debug and are not checked during production execution, indeed the program should never assume that assertions are being checked. Design By Contract uses three kinds of assertions: pre-conditions, post-conditions, and invariants.

(Quelle: http://www.cs.unc.edu/~stotts/145/CRC/DesByContract.html, Einsichtsdatum: 23.12.2019)