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

// environment
definition nonzero(address account) returns bool = account != 0;
definition nonpayable(env e) returns bool = e.msg.value == 0;
definition nonzerosender(env e) returns bool = nonzero(e.msg.sender);
definition sanity(env e) returns bool = clock(e) > 0 && clock(e) <= max_uint48;

// 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;

// time
definition clock(env e) returns mathint = to_mathint(e.block.timestamp);
definition isSetAndPast(env e, uint48 timepoint) returns bool = timepoint != 0 && to_mathint(timepoint) <= clock(e);