public void DecreasingIndentation_ByMustBeGreaterThanZero()
{
var sw = new StringWriter();
var iw = new IndentingTextWriter(sw, " ");
Assert.Throws <ArgumentOutOfRangeException>(() => iw.DecreaseIndentation(0));
Assert.Throws <ArgumentOutOfRangeException>(() => iw.DecreaseIndentation(-42));
}