Add debugging logging

Wow. Fantastic work. I only found nitpicks:

1. +++ b/email_verify.admin.inc
   @@ -52,6 +52,53 @@ function email_verify_admin_settings($form, &$form_state) {
   +    '#states' => array('enabled' => array(':input[name="email_verify_debug_mode"]' => array('checked' => TRUE))),
   

   This is a bit hard to read. Might be better on separate lines.

2. +++ b/email_verify.admin.inc
   @@ -52,6 +52,53 @@ function email_verify_admin_settings($form, &$form_state) {
   +    '#states' => array('enabled' => array(':input[name="email_verify_debug_mode"]' => array('checked' => TRUE))),
   

   Same as above.

3. +++ b/email_verify.admin.inc
   @@ -52,6 +52,53 @@ function email_verify_admin_settings($form, &$form_state) {
   +//  $options = array('loose' => t('Loose (fail for some failures)'), 'medium' => t('Medium (fail for most common failures)'), 'strict' => t('Strict (fail for all failed checks)'));
   +//  $form['email_verify_modes']['email_verify_verification_mode'] = array(
   +//    '#type' => 'select',
   +//    '#title' => t('Check for any DNS records'),
   +//    '#options' => $options,
   +//    '#default_value' => variable_get('email_verify_verification_mode', 1),
   +//    '#description' => t("Use PHP's checkdnsrr() function to see if there are any DNS records associated with the email address' domain name."),
   +//  );
   

   Commented-out code.

4. +++ b/email_verify.admin.inc
   @@ -124,7 +171,17 @@ function email_verify_admin_settings_submit($form, &$form_state) {
   +        // Log and/or display the debugging information.
   +        $message = implode('<br />', $debugging_text);
   +        if (variable_get('email_verify_debug_mode_record_log', FALSE)) {
   +          watchdog('email_verify debug', $message, array(), WATCHDOG_DEBUG);
   +        }
   +        if (variable_get('email_verify_debug_mode_display_page', FALSE)) {
   +          drupal_set_message($message);
   +        }
   +      }
   

   This is used more than once so add helper function?

5. +++ b/email_verify.admin.inc
   @@ -124,7 +171,17 @@ function email_verify_admin_settings_submit($form, &$form_state) {
   +          watchdog('email_verify debug', $message, array(), WATCHDOG_DEBUG);
   

   Maybe just 'email_verify' would be better? I think just the module name is typically used.

6. +++ b/email_verify.check.inc
   @@ -201,16 +201,26 @@ function _email_verify_batch_display_process_batch($user_count, $offset, $disabl
   +      // Log and/or display the debugging information.
   +      $message = implode('<br />', $check_results['debugging_text']);
   +      if (variable_get('email_verify_debug_mode_record_log', FALSE)) {
   +        watchdog('email_verify debug', $message, array(), WATCHDOG_DEBUG);
   +      }
   +      if (variable_get('email_verify_debug_mode_display_page', FALSE)) {
   +        drupal_set_message($message);
   +      }
   

   Use helper function?

7. +++ b/email_verify.module
   @@ -126,8 +126,20 @@ function email_verify_form_registration_form_alter(&$form, &$form_state, $form_i
   +      // Log and/or display the debugging information.
   +      $message = implode('<br />', $results['debugging_text']);
   +      if (variable_get('email_verify_debug_mode_record_log', FALSE)) {
   +        watchdog('email_verify debug', $message, array(), WATCHDOG_DEBUG);
   +      }
   +      if (variable_get('email_verify_debug_mode_display_page', FALSE)) {
   +        drupal_set_message($message);
   +      }
   

   Use helper function?

We'll get this tested soon.

Testing for the patch in comment #8.

Putting the debugging GUI inside /admin/config/system/email_verify is great, and allows for easy customization of the debugging options.

I tested this on a form I had and the output is very good. It printed it right at the top of the page (feels similar to how the devel module would show you debugging outputs which is a positive thing).

I also particularly like how the debugging has a blue background and the reason for why the email address was not validated has the yellow background. This makes things easier to know which is which just based off of background color. I attached a screenshot to point out what I mean by this.

This has passed testing.

Thanks!