diff --git a/src/applications/files/transform/__tests__/PhabricatorFileTransformTestCase.php b/src/applications/files/transform/__tests__/PhabricatorFileTransformTestCase.php
--- a/src/applications/files/transform/__tests__/PhabricatorFileTransformTestCase.php
+++ b/src/applications/files/transform/__tests__/PhabricatorFileTransformTestCase.php
@@ -2,9 +2,33 @@
 
 final class PhabricatorFileTransformTestCase extends PhabricatorTestCase {
 
+  protected function getPhabricatorTestCaseConfiguration() {
+    return array(
+      self::PHABRICATOR_TESTCONFIG_BUILD_STORAGE_FIXTURES => true,
+    );
+  }
+
   public function testGetAllTransforms() {
     PhabricatorFileTransform::getAllTransforms();
     $this->assertTrue(true);
   }
 
+  public function testThumbTransformDefaults() {
+    $xforms = PhabricatorFileTransform::getAllTransforms();
+    $file = new PhabricatorFile();
+
+    foreach ($xforms as $xform) {
+      if (!($xform instanceof PhabricatorFileThumbnailTransform)) {
+        continue;
+      }
+
+      // For thumbnails, generate the default thumbnail. This should be able
+      // to generate something rather than throwing an exception because we
+      // forgot to add a default file to the builtin resources. See T12614.
+      $xform->getDefaultTransform($file);
+
+      $this->assertTrue(true);
+    }
+  }
+
 }