View source for Design by contract

'''Design by contract''' ('''DbC'''), also known as '''contract programming''', ''programming by contract'' and ''design-by-contract programming'', is an approach for designing [[software]].

It prescribes that software designers should define formal, precise and verifiable interface specifications for [[Component-based_software_engineering|software components]], which extend the ordinary definition of [[Abstract data type|abstract data types]] with preconditions, postconditions and invariants.

These specifications are referred to as "contracts", in accordance with a conceptual metaphor with the conditions and obligations of business contracts.

The DbC approach assumes all client components that invoke an operation on a server component will meet the preconditions specified as required for that operation.

Where this assumption is considered too risky (as in multi-channel client-server or distributed computing) the opposite "defensive design" approach is taken, meaning that a server component tests (before or while processing a client's request) that all relevant preconditions hold true, and replies with a suitable error message if not.

== External links ==

* [https://en.wikipedia.org/wiki/Design_by_contract Design by contract] @ Wikipedia