Refactor postcode validation test cases

- Updated the invalid postcode test cases to correctly reflect the expected output after formatting.
- Ensured that postcodes with spaces and dashes are processed to remove those characters before validation.
- Added test cases for both valid and invalid postcodes according to the specified regex pattern.

tests/Formatter/ROFormatterTest.php

@@ -37,6 +37,33 @@ public function providerFormat() : array
             ['ABCD', null],
             ['ABCDE', null],
             ['ABCDEF', null],
+
+            // valid
+            ['123-456', '123456'],
+            ['  123456 ', '123456'],
+            ['010101', '010101'],
+            ['123456', '123456'],
+            ['090123', '090123'],
+            ['080456', '080456'],
+            ['070789', '070789'],
+            ['123450', '123450'],
+            ['012345', '012345'],
+            ['202020', '202020'],
+            ['999999', '999999'],
+
+            // invalid
+            ['000123', null],
+            ['01111', null],
+            ['000000', null],
+            ['-1234', null],
+            ['12ABCD', null],
+            ['12345678', null],
+            ['01 234 56', null],
+            ['0300!', null],
+            ['999999', null],
+            ['12 345', null],
+            ['07-089', null]
+
         ];
     }
 }