public void FallbackEmptyDefault()
{
Buffer b = NewInstance();
Assert.IsTrue(b.Fallback('X', 0), "#0");
Assert.IsFalse(b.MovePrevious(), "#1");
Assert.AreEqual(1, b.Remaining, "#2");
Assert.AreEqual('?', b.GetNextChar(), "#3");
Assert.AreEqual(0, b.Remaining, "#4");
// the string is already consumed.
Assert.AreEqual(char.MinValue, b.GetNextChar(), "#5");
}