diff --git includes/common.inc includes/common.inc
index e749880..448da25 100644
--- includes/common.inc
+++ includes/common.inc
@@ -4756,6 +4756,62 @@ function drupal_cron_cleanup() {
 }
 
 /**
+ * Add directories to search for system object files (modules, themes, etc.).
+ *
+ * This function is used to add directories to be searched when we build
+ * the system table. Modules found in these locations will override objects in
+ * the /modules/ and /profiles/your_site_profile/modules/ directories,
+ * but modules in the /sites/all/modules/ and /sites/your_site_dir/modules/
+ * directories will take precedence over them.
+ *
+ * @param $scope
+ *   The directory type to be added. May be one of the following:
+ *   - host_profile
+ * @param $directory
+ *   The path to be added.
+ */
+function drupal_add_system_directory($scope = null, $directory = null) {
+  static $search_dirs = array();
+
+  // Pre-load the directory array with the know directory scopes.
+  if (!sizeof($search_dirs)) {
+
+    // The active install profile directory for the host site from within a test.
+    // If no test is active no host profile directory will be set.
+    $search_dirs['host_profile'] = NULL;
+  }
+
+  // Return the entire list of directories.
+  if (is_null($scope) && is_null($directory)) {
+    return $search_dirs;
+  }
+
+  if (!is_null($directory) && !is_null($scope)) {
+    $search_dirs[$scope] = $directory;
+  }
+
+  if (array_key_exists($scope, $search_dirs)) {
+    return $search_dirs[$scope];
+  }
+
+  return FALSE;
+}
+
+/**
+ * Returns directories searched for system object files (modules, themes etc.).
+ *
+ * This function is used to return the directories that have been added with
+ * drupal_add_system_directory().
+ *
+ * @return
+ *   Array containing directory paths.
+ */
+function drupal_get_system_directory() {
+  return drupal_add_system_directory();
+}
+
+
+/**
  * Returns information about system object files (modules, themes, etc.).
  *
  * This function is used to find all or some system object files (module files,
@@ -4818,6 +4874,13 @@ function drupal_system_listing($mask, $directory, $key = 'name', $min_depth = 1)
     $searchdir[] = "profiles/$profile/$directory";
   }
 
+  // Include directories from the drupal_add_system_directory() function.
+  foreach (drupal_get_system_directory() as $additional_dir) {
+    if (!is_null($additional_dir)) {
+      $searchdir[] = "$additional_dir/$directory";
+    }
+  }
+
   // Always search sites/all/* as well as the global directories
   $searchdir[] = 'sites/all/' . $directory;
 
diff --git modules/simpletest/drupal_web_test_case.php modules/simpletest/drupal_web_test_case.php
index b32406c..1a4e92b 100644
--- modules/simpletest/drupal_web_test_case.php
+++ modules/simpletest/drupal_web_test_case.php
@@ -1188,6 +1188,11 @@ class DrupalWebTestCase extends DrupalTestCase {
     $this->originalProfile = drupal_get_profile();
     $clean_url_original = variable_get('clean_url', 0);
 
+    // The host profile's collection of modules or themes need to be included
+    // when running tests that use an alternate install profile but still reside
+    // in the host profile's directory.
+    drupal_add_system_directory('host_profile', 'profiles/' . $this->originalProfile);
+
     // Save and clean shutdown callbacks array because it static cached and
     // will be changed by the test run. If we don't, then it will contain
     // callbacks from both environments. So testing environment will try