diff --git a/core/modules/simpletest/tests/form.test b/core/modules/simpletest/tests/form.test
index 49933c3..754ce72 100644
--- a/core/modules/simpletest/tests/form.test
+++ b/core/modules/simpletest/tests/form.test
@@ -122,11 +122,11 @@ class FormsTestCase extends DrupalWebTestCase {
   }
 
   /**
-   * Tests #required checkboxes and radios.
+   * Tests validation for required checkbox, select, and radio elements.
    *
-   * Programmatically submits a test form containing several types of input
-   * elements. The form is submitted twice, once with values and once without,
-   * and each is checked for the proper #required error messages.
+   * Submits a test form containing several types of form elements. The form
+   * is submitted twice, first without values for required fields and then
+   * with values. Each submission is checked for relevant error messages. 
    *
    * @see form_test_validate_required_form()
    */
@@ -134,18 +134,38 @@ class FormsTestCase extends DrupalWebTestCase {
     $form = $form_state = array();
     $form = form_test_validate_required_form($form, $form_state);
 
-    // Verify each error message shows when required value not selected.
+    // Attempt to submit the form with no required fields set.
     $edit = array();
     $this->drupalPost('form-test/validate-required', $edit, 'Submit');
 
+    // The only error messages that should appear are the relevant 'required'
+    // messages for each field.
+    $expected = array();
     foreach (array('textfield', 'checkboxes', 'select', 'radios') as $key) {
-      $this->assertText(t('!name field is required.', array('!name' => $form[$key]['#title'])));
+      $expected[] = t('!name field is required.', array('!name' => $form[$key]['#title']));
     }
 
-    // The unhelpful catch-all generic error should not appear.
-    $this->assertNoText(t('An illegal choice has been detected. Please contact the site administrator.'));
+    // Check the page for error messages.
+    $errors = $this->xpath('//div[contains(@class, "error")]//li');
+    foreach ($errors as $error) {
+      $expected_key = array_search($error[0], $expected);
+      // If the error message is not one of the expected messages, fail.
+      if ($expected_key === FALSE) {
+        $this->fail("Invalid error message: {$error[0]}");
+      }
+      // Remove the expected message from the list once it is found.
+      else {
+        unset($expected[$expected_key]);
+      }
+    }
 
-    // Verify that no error appears with valid values.
+    // Fail if any expected messages were not found.
+    foreach ($expected as $not_found) {
+      $this->fail("Error message not shown: $not_found");
+    }
+
+    // Submit again with required fields set and verify that there are no
+    // error messages.
     $edit = array(
       'textfield' => $this->randomString(),
       'checkboxes[foo]' => TRUE,
@@ -153,11 +173,7 @@ class FormsTestCase extends DrupalWebTestCase {
       'radios' => 'bar',
     );
     $this->drupalPost('form-test/validate-required', $edit, 'Submit');
-
-    foreach (array('textfield', 'checkboxes', 'select', 'radios') as $key) {
-      $this->assertNoText(t('!name field is required.', array('!name' => $form[$key]['#title'])));
-    }
-    $this->assertNoText(t('An illegal choice has been detected. Please contact the site administrator.'));
+    $this->assertNoFieldByXpath('//div[contains(@class, "error")]', FALSE, 'No error message is displayed when all required fields are filled.');
   }
 
   /**