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/fact/engine/__tests__/PhabricatorFactEngineTestCase.php

@@ -0,0 +1,10 @@
+<?php
+
+final class PhabricatorFactEngineTestCase extends PhabricatorTestCase {
+
+  public function testLoadAllEngines() {
+    PhabricatorFactEngine::loadAllEngines();
+    $this->assertTrue(true);
+  }
+
+}