def _isvalid_partition(flux_components):
    """Test if partitioned flux directions (signs) are valid."""
    fc = flux_components
    isvalid = True
    mssg = ''
    if fc.Fqt <= 0:
        isvalid = False
        mssg += 'Fqt <= 0; '
    if fc.Fqe <= 0:
        isvalid = False
        mssg += 'Fqe <= 0; '
    if fc.Fcp >= 0:
        isvalid = False
        mssg += 'Fcp >= 0; '
    if fc.Fcr <= 0:
        isvalid = False
        mssg += 'Fcr <= 0; '
    return isvalid, mssg
