public void PreviousIndex_Test()
{
Assert.Equal(6, Notes.C.PreviousIndex);
Assert.Equal(0, Notes.D.PreviousIndex);
Assert.Equal(1, Notes.E.PreviousIndex);
Assert.Equal(2, Notes.F.PreviousIndex);
Assert.Equal(3, Notes.G.PreviousIndex);
Assert.Equal(4, Notes.A.PreviousIndex);
Assert.Equal(5, Notes.B.PreviousIndex);
}