SELECT
   code,
   format,
   to_char(code, format) AS out,
   to_char(code, format) = expect AS pass
FROM (
   VALUES
   ('EC4Y 0HQ'::postcode, 'AD SW', 'EC4Y 0HQ'),
   ('EC4Y 0HQ'::postcode, 'ADSW', 'EC4Y0HQ'),
   ('EC4Y 0HQ'::postcode, 'ADSW', 'EC4Y0HQ'),
   ('EC4Y 0HQ'::postcode, 'AD', 'EC4Y'),
   ('EC4Y 0HQ'::postcode, 'SW', '0HQ'),
   ('EC4Y 0HQ'::postcode, 'A', 'EC'),
   ('EC4Y 0HQ'::postcode, 'D', '4Y'),
   ('EC4Y 0HQ'::postcode, 'S', '0'),
   ('EC4Y 0HQ'::postcode, 'W', 'HQ'),
   ('EC4Y 0HQ'::postcode, ' AD SW ', ' EC4Y 0HQ '),
   ('EC4Y 0HQ'::postcode, '-AD SW-', '-EC4Y 0HQ-'),
   ('EC4Y 0HQ'::postcode, '', ''),
   ('EC4Y 0HQ'::postcode, 'test', 'test'),
   ('EC4Y 0HQ'::postcode, E'A\nD\nS\nW', E'EC\n4Y\n0\nHQ'),
   ('EC4Y 0HQ'::postcode, 'ADAD', 'EC4YEC4Y'),
   ('EC4Y 0HQ'::postcode, 'AA', 'ECEC'),
   ('EC4Y 0HQ'::postcode, 'A A', 'EC EC'),
   ('EC4Y 0HQ'::postcode, ' D D ', ' 4Y 4Y '),
   ('EC4Y 0HQ'::postcode, 'WW', 'HQHQ'),
   ('EC4Y 0HQ'::postcode, 'WSW', 'HQ0HQ'),
   ('SW1A 1AA'::postcode, 'W', 'AA'),
   ('BX5 5AT'::postcode, 'DD', '55'),
   ('BX5 5AT'::postcode, 'AD SW', 'BX5 5AT'),
   ('BX5 5AT'::postcode, 'ADSW', 'BX55AT'),
   ('BX5 5AT'::postcode, '.ADSW.ADSW.', '.BX55AT.BX55AT.'),
   ('G58 1SB'::postcode, 'ADSW', 'G581SB'),
   ('G58 1SB'::postcode, 'AD SW', 'G58 1SB'),
   ('G58 1SB'::postcode, 'AA', 'GG'),
   ('G58 1SB'::postcode, 'SWAAD', '1SBGG58'),
   ('G58 1SB'::postcode, '.SWAAD-', '.1SBGG58-')
) AS sample (code, format, expect)
ORDER BY to_char(code, format) = expect ASC
   code   |   format    |       out       | pass 
----------+-------------+-----------------+------
 EC4Y 0HQ | AD SW       | EC4Y 0HQ        | t
 EC4Y 0HQ | ADSW        | EC4Y0HQ         | t
 EC4Y 0HQ | ADSW        | EC4Y0HQ         | t
 EC4Y 0HQ | AD          | EC4Y            | t
 EC4Y 0HQ | SW          | 0HQ             | t
 EC4Y 0HQ | A           | EC              | t
 EC4Y 0HQ | D           | 4Y              | t
 EC4Y 0HQ | S           | 0               | t
 EC4Y 0HQ | W           | HQ              | t
 EC4Y 0HQ |  AD SW      |  EC4Y 0HQ       | t
 EC4Y 0HQ | -AD SW-     | -EC4Y 0HQ-      | t
 EC4Y 0HQ |             |                 | t
 EC4Y 0HQ | test        | test            | t
 EC4Y 0HQ | A          +| EC             +| t
          | D          +| 4Y             +| 
          | S          +| 0              +| 
          | W           | HQ              | 
 EC4Y 0HQ | ADAD        | EC4YEC4Y        | t
 EC4Y 0HQ | AA          | ECEC            | t
 EC4Y 0HQ | A A         | EC EC           | t
 EC4Y 0HQ |  D D        |  4Y 4Y          | t
 EC4Y 0HQ | WW          | HQHQ            | t
 EC4Y 0HQ | WSW         | HQ0HQ           | t
 SW1A 1AA | W           | AA              | t
 BX5 5AT  | DD          | 55              | t
 BX5 5AT  | AD SW       | BX5 5AT         | t
 BX5 5AT  | ADSW        | BX55AT          | t
 BX5 5AT  | .ADSW.ADSW. | .BX55AT.BX55AT. | t
 G58 1SB  | ADSW        | G581SB          | t
 G58 1SB  | AD SW       | G58 1SB         | t
 G58 1SB  | AA          | GG              | t
 G58 1SB  | SWAAD       | 1SBGG58         | t
 G58 1SB  | .SWAAD-     | .1SBGG58-       | t
(30 rows)