openzeppelin-contracts/certora/specs/helpers/helpers.spec

// environment
definition nonpayable(env e) returns bool = e.msg.value == 0;
definition nonzerosender(env e) returns bool = e.msg.sender != 0;

// math
definition min(mathint a, mathint b) returns mathint = a < b ? a : b;
definition max(mathint a, mathint b) returns mathint = a > b ? a : b;