public void Backspace()
{
//0123456789012345678901234
var sut = new LineEditor("ab cd efg hijklmn op qrst", 5);
var index = sut.Backspace(12);
Assert.AreEqual(11, index);
//012345678901234567890123
Assert.AreEqual("ab cd efg hjklmn op qrst", sut.Line);
Assert.AreEqual(new[] { "ab cd ", "efg ", "hjklm", "n op ", "qrst" }, sut.SoftLines);
index = sut.Backspace(24);
Assert.AreEqual(23, index);
Assert.AreEqual("ab cd efg hjklmn op qrs", sut.Line);
Assert.AreEqual(new[] { "ab cd ", "efg ", "hjklm", "n op ", "qrs" }, sut.SoftLines);
}