Add a bunch of tests for subclass implementations

Summary: Add a bunch of tests to ensure that subclasses behave.

Test Plan: `arc unit`

Reviewers: eadler, #blessed_reviewers, epriestley

Reviewed By: eadler, #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D13272

src/applications/phid/type/PhabricatorPHIDType.php

@@ -158,7 +158,7 @@ abstract class PhabricatorPHIDType extends Phobject {
    *
    * @return dict<string, PhabricatorPHIDType> Map of type constants to types.
    */
-  public static function getAllTypes() {
+  final public static function getAllTypes() {
     static $types;
     if ($types === null) {
       $objects = id(new PhutilSymbolLoader())

src/applications/phid/type/__tests__/PhabricatorPHIDTypeTestCase.php

@@ -0,0 +1,10 @@
+<?php
+
+final class PhabricatorPHIDTypeTestCase extends PhutilTestCase {
+
+  public function testGetAllTypes() {
+    PhabricatorPHIDType::getAllTypes();
+    $this->assertTrue(true);
+  }
+
+}