public void SplitAtTest()
{
var s = new StyledText("abcd", Color.Black);
StyledText l;
StyledText r;
s.SplitAt(0, out l, out r);
Assert.AreEqual("", l.Text);
Assert.AreEqual("abcd", r.Text);
Assert.AreEqual(Color.Black, l.Color);
Assert.AreEqual(Color.Black, r.Color);
s.SplitAt(1, out l, out r);
Assert.AreEqual("a", l.Text);
Assert.AreEqual("bcd", r.Text);
Assert.AreEqual(Color.Black, l.Color);
Assert.AreEqual(Color.Black, r.Color);
s.SplitAt(2, out l, out r);
Assert.AreEqual("ab", l.Text);
Assert.AreEqual("cd", r.Text);
Assert.AreEqual(Color.Black, l.Color);
Assert.AreEqual(Color.Black, r.Color);
s.SplitAt(3, out l, out r);
Assert.AreEqual("abc", l.Text);
Assert.AreEqual("d", r.Text);
Assert.AreEqual(Color.Black, l.Color);
Assert.AreEqual(Color.Black, r.Color);
s.SplitAt(4, out l, out r);
Assert.AreEqual("abcd", l.Text);
Assert.AreEqual("", r.Text);
Assert.AreEqual(Color.Black, l.Color);
Assert.AreEqual(Color.Black, r.Color);
Assert.Throws <ArgumentOutOfRangeException>(() => s.SplitAt(-1, out l, out r));
Assert.Throws <ArgumentOutOfRangeException>(() => s.SplitAt(5, out l, out r));
}