import std.algorithm.comparison : equal;

auto set = CodepointSet('a', 'z'+1, 'а', 'я'+1);
foreach (v; 'a'..'z'+1)
    assert(set[v]);
// Cyrillic lowercase interval
foreach (v; 'а'..'я'+1)
    assert(set[v]);
//specific order is not required, intervals may interesect
auto set2 = CodepointSet('а', 'я'+1, 'a', 'd', 'b', 'z'+1);
//the same end result
assert(set2.byInterval.equal(set.byInterval));
// test constructor this(Range)(Range intervals)
auto chessPiecesWhite = CodepointInterval(9812, 9818);
auto chessPiecesBlack = CodepointInterval(9818, 9824);
auto set3 = CodepointSet([chessPiecesWhite, chessPiecesBlack]);
foreach (v; '♔'..'♟'+1)
    assert(set3[v]);