[ticket/11541] Add unit tests for style_select()

PHPBB3-11541
Merge remote-tracking branch 'nickvergessen/ticket/11541' into develop-olympus

* nickvergessen/ticket/11541:
  [ticket/11541] Add unit tests for style_select()
Merge branch 'develop-olympus' into develop

* develop-olympus:
  [ticket/11541] Add unit tests for style_select()