diff --git a/docker-compose.yml b/docker-compose.yml
index 6a5b27d483..cf7402ef0a 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -44,6 +44,7 @@ services:
       SMTP_PORT: 1025
       SMTP_USER: ~
       SMTP_PASSWORD: ~
+      TEST_MAILCATCHER_URL: "http://mailcatcher:1080"
     networks:
       - backend
 
diff --git a/eccube_install.sh b/eccube_install.sh
index d21cbb13df..81290dd605 100755
--- a/eccube_install.sh
+++ b/eccube_install.sh
@@ -210,6 +210,7 @@ defined('SMTP_HOST') or define('SMTP_HOST', '${SMTP_HOST}');
 defined('SMTP_PORT') or define('SMTP_PORT', '${SMTP_PORT}');
 defined('SMTP_USER') or define('SMTP_USER', '${SMTP_USER}');
 defined('SMTP_PASSWORD') or define('SMTP_PASSWORD', '${SMTP_PASSWORD}');
+defined('TEST_MAILCATCHER_URL') or define('TEST_MAILCATCHER_URL', '${TEST_MAILCATCHER_URL-"http://127.0.0.1:1080"}');
 
 __EOF__
 
diff --git a/tests/class/Common_TestCase.php b/tests/class/Common_TestCase.php
index f3e006a132..770115ca1b 100644
--- a/tests/class/Common_TestCase.php
+++ b/tests/class/Common_TestCase.php
@@ -18,9 +18,6 @@
  */
 class Common_TestCase extends PHPUnit_Framework_TestCase
 {
-    /** MailCatcher の URL. */
-    const MAILCATCHER_URL = 'http://127.0.0.1:1080';
-
     /**
      * MDB2 をグローバル変数のバックアップ対象から除外する。
      *
@@ -49,6 +46,9 @@ protected function setUp()
         $this->objQuery = SC_Query_Ex::getSingletonInstance('', true);
         $this->objQuery->begin();
         $this->objGenerator = new \Eccube2\Tests\Fixture\Generator($this->objQuery);
+        if (!defined('TEST_MAILCATCHER_URL')) {
+            $this->markTestSkipped('TEST_MAILCATCHER_URL is not defined.');
+        }
     }
 
     protected function tearDown()
@@ -77,14 +77,18 @@ protected function checkMailCatcherStatus()
             $context = stream_context_create(array(
                 'http' => array('ignore_errors' => true)
             ));
-            $response = file_get_contents(self::MAILCATCHER_URL.'/messages', false, $context);
+            $response = file_get_contents(TEST_MAILCATCHER_URL.'/messages', false, $context);
 
             $http_status = strpos($http_response_header[0], '200');
             if ($http_status === false) {
-                $this->markTestSkipped('MailCatcher is not available');
+                throw new Exception('Response code is not 200: $http_response_header[0] = ' . var_export($http_response_header[0], true));
+            }
+
+            if ($response === false) {
+                throw new Exception('file_get_contents response is false.');
             }
         } catch (Exception $e) {
-            $this->markTestSkipped('MailCatcher is not available');
+            $this->markTestSkipped('MailCatcher is not available: ' . $e->getMessage());
         }
     }
 
@@ -102,7 +106,7 @@ protected function resetEmails()
                 )
             );
 
-            file_get_contents(self::MAILCATCHER_URL.'/messages', false, $context);
+            file_get_contents(TEST_MAILCATCHER_URL.'/messages', false, $context);
 
         } catch (\Exception $e) {
             // quiet
@@ -116,7 +120,7 @@ protected function resetEmails()
      */
     protected function getMailCatcherMessages()
     {
-        return json_decode(file_get_contents(self::MAILCATCHER_URL. '/messages'), true);
+        return json_decode(file_get_contents(TEST_MAILCATCHER_URL. '/messages'), true);
     }
 
     /**
@@ -127,7 +131,7 @@ protected function getMailCatcherMessages()
      */
     protected function getMailCatcherMessage($message)
     {
-        $source = file_get_contents(self::MAILCATCHER_URL. '/messages/'.$message['id'].'.source');
+        $source = file_get_contents(TEST_MAILCATCHER_URL. '/messages/'.$message['id'].'.source');
 
         $message['source'] = quoted_printable_decode($source);
         $message['source'] = mb_convert_encoding($message['source'], 'UTF-8', 'JIS');
diff --git a/tests/class/SC_SendMailTest.php b/tests/class/SC_SendMailTest.php
index 05324789a7..409337b8af 100644
--- a/tests/class/SC_SendMailTest.php
+++ b/tests/class/SC_SendMailTest.php
@@ -167,15 +167,8 @@ public function testGetBackendParams()
         $this->verify();
 
         $this->expected = [
-            'host' => '127.0.0.1',
-            'port' => '1025'
-        ];
-        $this->actual = $this->objSendMail->getBackendParams('smtp');
-        $this->verify();
-
-        $this->expected = [
-            'host' => '127.0.0.1',
-            'port' => '1025'
+            'host' => SMTP_HOST,
+            'port' => SMTP_PORT,
         ];
         $this->actual = $this->objSendMail->getBackendParams('smtp');
         $this->verify();