use module test_m_replace() { echo("==== test_m_replace ===="); original_m = [ [1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12] ]; expected = [ [1, 2, 3, 4], [5, 6, 70, 8], [9, 10, 11, 12] ]; actual = m_replace(original_m, 1, 2, 70); assert(actual == expected); } test_m_replace();