public void FindWordBoundary()
{
var str = " hello world test \t \U0002F8B6\U0002F8D3b ok\0";
Assert.AreEqual(new Pair <int>(0, 2), Unicode.FindWordBoundary(str, 0));
Assert.AreEqual(new Pair <int>(0, 2), Unicode.FindWordBoundary(str, 1));
Assert.AreEqual(new Pair <int>(2, 7), Unicode.FindWordBoundary(str, 2));
Assert.AreEqual(new Pair <int>(2, 7), Unicode.FindWordBoundary(str, 4));
Assert.AreEqual(new Pair <int>(24, 29), Unicode.FindWordBoundary(str, 24));
Assert.AreEqual(new Pair <int>(24, 29), Unicode.FindWordBoundary(str, 25));
}