Function test_map_iterator_arithmetic

tests/test_container_helpers.h:842–859

// Verifies: operator+, operator-, distance calculations
template<template<typename, typename> class MapTemplate>
void test_map_iterator_arithmetic() {
    using MapContainer = MapTemplate<int, fl::shared_ptr<int>>;

    MapContainer c;
    populate_map(c, 1, make_shared_int(10));
    populate_map(c, 2, make_shared_int(20));
    populate_map(c, 3, make_shared_int(30));

    // Test operator+ on iterators
    auto it0 = c.begin();
    auto it1 = c.begin() + 1;
    auto it2 = c.begin() + 2;

    FL_CHECK(it1 - it0 == 1);  // Distance check
    FL_CHECK(it2 - it0 == 2);
    FL_CHECK(it1 != it0);
    FL_CHECK(it1 != it2);
}

// Test map iteration with key-value access
// Verifies: pair<Key, Value> dereferencing