PASS '+1 555 010 0001'            -> '+1 555 010 0001'
PASS '555-010-0002'               -> '555-010-0002'
PASS '+44 20 7946 0958'           -> '+44 20 7946 0958'
PASS '(555) 123-4567'             -> '(555) 123-4567'
PASS '(555)1234567'               -> '(555)1234567'
PASS '555.123.4567'               -> '555.123.4567'
PASS '5551234567'                 -> '5551234567'
PASS '+1 (555) 123-4567'          -> '+1 (555) 123-4567'
PASS '020 7946 0958'              -> '020 7946 0958'
REJECT '12345'                      -> None
REJECT '1234'                       -> None
PASS '+1 555 010 0001 ext 22'     -> '+1 555 010 0001 ext 22'
PASS '555 123 4567'               -> '555 123 4567'
PASS '+91 98765 43210'            -> '+91 98765 43210'
PASS '1-800-555-0199'             -> '1-800-555-0199'
PASS '07555 123 456'              -> '07555 123 456'
PASS '966 55 123 4567'            -> '966 55 123 4567'
REJECT '555'                        -> None
REJECT '12'                         -> None
REJECT 'not a phone'                -> None
REJECT '+'                          -> None
REJECT 'tel: 5551234567'            -> None
REJECT 'call me at 5'               -> None
REJECT '5551234567890123456789'     -> None

digits_only("+1 555 010 0001") == digits_only("555-010-0001"): False