Edge Case

An edge case is a situation that occurs at the extreme ends of input, operating conditions, or environment. It requires exceptional conditions to happen, yet it is a possible situation.

<?php

// PHP addition always returns an integer
$integer = 2 + 1;

// adding positive values to PHP_INT_MAX is an edge case
$integer = PHP_INT_MAX + 1;

?>

Related : Coverage, Overflow, Test, Unit Test