core/includes/form.inc                         |    6 +++-
 core/modules/simpletest/tests/form.test        |    9 ++++---
 core/modules/simpletest/tests/form_test.module |   25 +++++++++++++++++------
 3 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/core/includes/form.inc b/core/includes/form.inc
index 9e99426..139a663 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -2258,8 +2258,10 @@ function form_type_radios_value(&$element, $input = FALSE) {
   if ($input !== FALSE) {
     // Check if the user submission had no value for this element.
     if (!isset($input)) {
-      // Flag as a garbage value so that form builder will not automatically
-      // replace the NULL value with an empty string.
+      // Flag as a garbage value. If the value is set to NULL and
+      // #has_garbage_value is not set then the form builder will automatically
+      // attempt to use default value or '' (an empty string). An empty string
+      // will fail validation because it is not in the allowed values list.
       $element['#has_garbage_value'] = TRUE;
       // There was a user submission so validation is a must. This way, the
       // required checker will produce an error as necessary.
diff --git a/core/modules/simpletest/tests/form.test b/core/modules/simpletest/tests/form.test
index c79a469..57b2616 100644
--- a/core/modules/simpletest/tests/form.test
+++ b/core/modules/simpletest/tests/form.test
@@ -136,7 +136,7 @@ class FormsTestCase extends DrupalWebTestCase {
 
     // Attempt to submit the form with no required fields set.
     $edit = array();
-    $this->drupalPost('form-test/validate-required', $edit, 'Submit');
+    $this->drupalPost('form-test/validate-required', $edit, t('Submit'));
 
     // The only error messages that should appear are the relevant 'required'
     // messages for each field.
@@ -151,7 +151,7 @@ class FormsTestCase extends DrupalWebTestCase {
       $expected_key = array_search($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]}");
+        $this->fail(format_string("Invalid error message: @error", array('@error' => $error[0])));
       }
       // Remove the expected message from the list once it is found.
       else {
@@ -161,7 +161,7 @@ class FormsTestCase extends DrupalWebTestCase {
 
     // Fail if any expected messages were not found.
     foreach ($expected as $not_found) {
-      $this->fail("Error message not shown: $not_found");
+      $this->fail(format_string("Error message not shown: @error", array('@error' => $not_found)));
     }
 
     // Submit again with required fields set and verify that there are no
@@ -172,8 +172,9 @@ class FormsTestCase extends DrupalWebTestCase {
       'select' => 'foo',
       'radios' => 'bar',
     );
-    $this->drupalPost('form-test/validate-required', $edit, 'Submit');
+    $this->drupalPost('form-test/validate-required', $edit, t('Submit'));
     $this->assertNoFieldByXpath('//div[contains(@class, "error")]', FALSE, 'No error message is displayed when all required fields are filled.');
+    $this->assertRaw("The form_test_validate_required_form form was submitted successfully.", 'Validation form submitted successfully.');
   }
 
   /**
diff --git a/core/modules/simpletest/tests/form_test.module b/core/modules/simpletest/tests/form_test.module
index 2173bcb..01db063 100644
--- a/core/modules/simpletest/tests/form_test.module
+++ b/core/modules/simpletest/tests/form_test.module
@@ -27,7 +27,8 @@ function form_test_menu() {
     'title' => 'Form #required validation',
     'page callback' => 'drupal_get_form',
     'page arguments' => array('form_test_validate_required_form'),
-    'access callback' => TRUE,
+    'access arguments' => array('access content'),
+    'type' => MENU_CALLBACK,
   );
   $items['form-test/limit-validation-errors'] = array(
     'title' => 'Form validation with some error suppression',
@@ -357,38 +358,48 @@ function form_test_validate_form_validate(&$form, &$form_state) {
 function form_test_validate_required_form($form, &$form_state) {
   $form['textfield'] = array(
     '#type' => 'textfield',
-    '#title' => 'Textfield',
+    '#title' => t('Textfield'),
     '#required' => TRUE,
   );
   $form['checkboxes'] = array(
     '#type' => 'checkboxes',
-    '#title' => 'Checkboxes',
+    '#title' => t('Checkboxes'),
     '#options' => drupal_map_assoc(array('foo', 'bar')),
     '#required' => TRUE,
   );
   $form['select'] = array(
     '#type' => 'select',
-    '#title' => 'Select',
+    '#title' => t('Select'),
     '#options' => drupal_map_assoc(array('foo', 'bar')),
     '#required' => TRUE,
   );
   $form['radios'] = array(
     '#type' => 'radios',
-    '#title' => 'Radios',
+    '#title' => t('Radios'),
     '#options' => drupal_map_assoc(array('foo', 'bar')),
     '#required' => TRUE,
   );
   $form['radios_optional'] = array(
     '#type' => 'radios',
-    '#title' => 'Radios (optional)',
+    '#title' => t('Radios (optional)'),
     '#options' => drupal_map_assoc(array('foo', 'bar')),
   );
   $form['actions'] = array('#type' => 'actions');
-  $form['actions']['submit'] = array('#type' => 'submit', '#value' => 'Submit');
+  $form['actions']['submit'] = array('#type' => 'submit', '#value' => t('Submit'));
   return $form;
 }
 
 /**
+ * Form submit handler to test for proper submission.
+ *
+ * This message is checked for in the tests to confirm that this for
+ * successfully submitted without any errors.
+ */
+function form_test_validate_required_form_submit($form, &$form_state) {
+  drupal_set_message("The form_test_validate_required_form form was submitted successfully.");
+}
+
+/**
  * Builds a simple form with a button triggering partial validation.
  */
 function form_test_limit_validation_errors_form($form, &$form_state) {