Private Function ModSymVerify()
    ' Test the ModSym function.

    Debug.Assert ModSym(5, 4) = 1
    Debug.Assert ModSym(4, 4) = 0
    Debug.Assert ModSym(3, 4) = -1
    Debug.Assert ModSym(2, 4) = -2
    Debug.Assert ModSym(1, 4) = 1
    Debug.Assert ModSym(0, 4) = 0
    Debug.Assert ModSym(-1, 4) = -1
    Debug.Assert ModSym(-2, 4) = -2
    Debug.Assert ModSym(-3, 4) = 1
    Debug.Assert ModSym(-4, 4) = 0
    Debug.Assert ModSym(-5, 4) = -1

    Debug.Assert ModSym(5, -4) = 1
    Debug.Assert ModSym(4, -4) = 0
    Debug.Assert ModSym(3, -4) = -1
    Debug.Assert ModSym(2, -4) = 2
    Debug.Assert ModSym(1, -4) = 1
    Debug.Assert ModSym(0, -4) = 0
    Debug.Assert ModSym(-1, -4) = -1
    Debug.Assert ModSym(-2, -4) = 2
    Debug.Assert ModSym(-3, -4) = 1
    Debug.Assert ModSym(-4, -4) = 0
    Debug.Assert ModSym(-5, -4) = -1

    Debug.Assert IsNull(ModSym(Null, 3))
    Debug.Assert IsNull(ModSym("Joe", 3))
    Debug.Assert IsNull(ModSym(3, Null))
    Debug.Assert IsNull(ModSym(3, "Joe"))

End Function