Eiffel had design by contract from way back. https://en.m.wikipedia.org/wiki/Eiffel_(programming_language) https://en.m.wikipedia.org/wiki/Eiffel_(programming_

Eiffel had design by contract from way back. https://en.m.wikipedia.org/wiki/Eiffel_(programming_language) https://en.m.wikipedia.org/wiki/Eiffel_(programming_language... https://en.m.wikipedia.org/wiki/Design_by_contract https://en.m.wikipedia.org/wiki/Design_by_contract Unfortunately it suffered from some of the same issues as Ada: For a long time, only expensive implementations available, and a somewhat verbose syntax.