Editing Class invariant (section)

===Assertions===

Common programming languages like Python,<ref>[https://docs.python.org/3/reference/simple_stmts.html#grammar-token-assert-stmt Official Python Docs, ''assert statement'']</ref> PHP,<ref>{{Cite web|title=PHP assert function|url=https://www.php.net/manual/en/function.assert.php|url-status=live|archive-url=https://web.archive.org/web/20010321003333/http://www.php.net:80/manual/en/function.assert.php |archive-date=2001-03-21 }}</ref> JavaScript,{{citation needed|date=February 2021}} C++ and Java support [[Assertion (computing)|assertions]] by default, which can be used to define class invariants. A common pattern to implement invariants in classes is for the constructor of the class to throw an exception if the invariant is not satisfied. Since methods preserve the invariants, they can assume the validity of the invariant and need not explicitly check for it.