diff --git a/apps/advanced/tests/codeception/backend/acceptance/_bootstrap.php b/apps/advanced/tests/codeception/backend/acceptance/_bootstrap.php
index 6ce3d175be..411855e3de 100644
--- a/apps/advanced/tests/codeception/backend/acceptance/_bootstrap.php
+++ b/apps/advanced/tests/codeception/backend/acceptance/_bootstrap.php
@@ -1,3 +1,2 @@
 <?php
-
-new yii\web\Application(require(__DIR__ . '/_config.php'));
+new yii\web\Application(require(dirname(dirname(__DIR__)) . '/config/backend/acceptance.php'));
diff --git a/apps/advanced/tests/codeception/backend/functional.suite.yml b/apps/advanced/tests/codeception/backend/functional.suite.yml
index b04e7c8b9c..8945473581 100644
--- a/apps/advanced/tests/codeception/backend/functional.suite.yml
+++ b/apps/advanced/tests/codeception/backend/functional.suite.yml
@@ -14,4 +14,4 @@ modules:
       - codeception\common\_support\FixtureHelper
     config:
         Yii2:
-            configFile: 'functional/_config.php'
+            configFile: '../config/backend/functional.php'
diff --git a/apps/advanced/tests/codeception/backend/functional/_bootstrap.php b/apps/advanced/tests/codeception/backend/functional/_bootstrap.php
index 6ce3d175be..94f3fbd5d7 100644
--- a/apps/advanced/tests/codeception/backend/functional/_bootstrap.php
+++ b/apps/advanced/tests/codeception/backend/functional/_bootstrap.php
@@ -1,3 +1,2 @@
 <?php
-
-new yii\web\Application(require(__DIR__ . '/_config.php'));
+new yii\web\Application(require(dirname(dirname(__DIR__)) . '/config/backend/functional.php'));
diff --git a/apps/advanced/tests/codeception/backend/unit/DbTestCase.php b/apps/advanced/tests/codeception/backend/unit/DbTestCase.php
index 6c400201c5..4f5a5fd352 100644
--- a/apps/advanced/tests/codeception/backend/unit/DbTestCase.php
+++ b/apps/advanced/tests/codeception/backend/unit/DbTestCase.php
@@ -4,5 +4,5 @@ namespace backend\tests\unit;
 
 class DbTestCase extends \yii\codeception\DbTestCase
 {
-    public $appConfig = '@backend/tests/unit/_config.php';
+    public $appConfig = '@codeception/config/backend/unit.php';
 }
diff --git a/apps/advanced/tests/codeception/backend/unit/TestCase.php b/apps/advanced/tests/codeception/backend/unit/TestCase.php
index 832f36e389..5fd4fbc632 100644
--- a/apps/advanced/tests/codeception/backend/unit/TestCase.php
+++ b/apps/advanced/tests/codeception/backend/unit/TestCase.php
@@ -4,5 +4,5 @@ namespace backend\tests\unit;
 
 class TestCase extends \yii\codeception\TestCase
 {
-    public $appConfig = '@backend/tests/unit/_config.php';
+    public $appConfig = '@codeception/config/backend/unit.php';
 }
diff --git a/apps/advanced/tests/codeception/bin/_console_bootstrap.php b/apps/advanced/tests/codeception/bin/_bootstrap.php
similarity index 100%
rename from apps/advanced/tests/codeception/bin/_console_bootstrap.php
rename to apps/advanced/tests/codeception/bin/_bootstrap.php
diff --git a/apps/advanced/tests/codeception/bin/yii_acceptance b/apps/advanced/tests/codeception/bin/yii_acceptance
index 116102ae49..b6dfafc758 100644
--- a/apps/advanced/tests/codeception/bin/yii_acceptance
+++ b/apps/advanced/tests/codeception/bin/yii_acceptance
@@ -8,19 +8,15 @@
  * @license http://www.yiiframework.com/license/
  */
 
-require_once __DIR__ . '/_console_bootstrap.php';
+require_once __DIR__ . '/_bootstrap.php';
 
 $config = yii\helpers\ArrayHelper::merge(
     require(ROOT_DIR . '/common/config/main.php'),
     require(ROOT_DIR . '/common/config/main-local.php'),
     require(ROOT_DIR . '/console/config/main.php'),
     require(ROOT_DIR . '/console/config/main-local.php'),
+    require(dirname(__DIR__) . '/config/acceptance.php'),
     [
-        'components' => [
-            'db' => [
-                'dsn' => 'mysql:host=localhost;dbname=yii2_advanced_acceptance',
-            ],
-        ],
         'controllerMap' => [
             'fixture' => [
                 'class' => 'yii\faker\FixtureController',
diff --git a/apps/advanced/tests/codeception/bin/yii_functional b/apps/advanced/tests/codeception/bin/yii_functional
index 480196e8c2..abf755ed28 100644
--- a/apps/advanced/tests/codeception/bin/yii_functional
+++ b/apps/advanced/tests/codeception/bin/yii_functional
@@ -8,19 +8,15 @@
  * @license http://www.yiiframework.com/license/
  */
 
-require_once __DIR__ . '/_console_bootstrap.php';
+require_once __DIR__ . '/_bootstrap.php';
 
 $config = yii\helpers\ArrayHelper::merge(
     require(ROOT_DIR . '/common/config/main.php'),
     require(ROOT_DIR . '/common/config/main-local.php'),
     require(ROOT_DIR . '/console/config/main.php'),
     require(ROOT_DIR . '/console/config/main-local.php'),
+    require(dirname(__DIR__) . '/config/functional.php'),
     [
-        'components' => [
-            'db' => [
-                'dsn' => 'mysql:host=localhost;dbname=yii2_advanced_functional',
-            ],
-        ],
         'controllerMap' => [
             'fixture' => [
                 'class' => 'yii\faker\FixtureController',
diff --git a/apps/advanced/tests/codeception/bin/yii_unit b/apps/advanced/tests/codeception/bin/yii_unit
index 04cedd0965..1187c6d50c 100644
--- a/apps/advanced/tests/codeception/bin/yii_unit
+++ b/apps/advanced/tests/codeception/bin/yii_unit
@@ -8,19 +8,15 @@
  * @license http://www.yiiframework.com/license/
  */
 
-require_once __DIR__ . '/_console_bootstrap.php';
+require_once __DIR__ . '/_bootstrap.php';
 
 $config = yii\helpers\ArrayHelper::merge(
     require(ROOT_DIR . '/common/config/main.php'),
     require(ROOT_DIR . '/common/config/main-local.php'),
     require(ROOT_DIR . '/console/config/main.php'),
     require(ROOT_DIR . '/console/config/main-local.php'),
+    require(dirname(__DIR__) . '/config/unit.php'),
     [
-        'components' => [
-            'db' => [
-                'dsn' => 'mysql:host=localhost;dbname=yii2_advanced_unit',
-            ],
-        ],
         'controllerMap' => [
             'fixture' => [
                 'class' => 'yii\faker\FixtureController',
diff --git a/apps/advanced/tests/codeception/common/unit/DbTestCase.php b/apps/advanced/tests/codeception/common/unit/DbTestCase.php
index 1a510d2df8..b4bd51f124 100644
--- a/apps/advanced/tests/codeception/common/unit/DbTestCase.php
+++ b/apps/advanced/tests/codeception/common/unit/DbTestCase.php
@@ -7,5 +7,5 @@ namespace codeception\common\unit;
  */
 class DbTestCase extends \yii\codeception\DbTestCase
 {
-    public $appConfig = '@codeception/common/unit/_config.php';
+    public $appConfig = '@codeception/config/common/unit.php';
 }
diff --git a/apps/advanced/tests/codeception/common/unit/TestCase.php b/apps/advanced/tests/codeception/common/unit/TestCase.php
index 6d85860ce8..e37282dea1 100644
--- a/apps/advanced/tests/codeception/common/unit/TestCase.php
+++ b/apps/advanced/tests/codeception/common/unit/TestCase.php
@@ -7,5 +7,5 @@ namespace common\tests\unit;
  */
 class TestCase extends \yii\codeception\TestCase
 {
-    public $appConfig = '@common/tests/unit/_config.php';
+    public $appConfig = '@codeception/config/common/unit.php';
 }
diff --git a/apps/advanced/tests/codeception/config/acceptance.php b/apps/advanced/tests/codeception/config/acceptance.php
new file mode 100644
index 0000000000..09f82007d9
--- /dev/null
+++ b/apps/advanced/tests/codeception/config/acceptance.php
@@ -0,0 +1,11 @@
+<?php
+/**
+ * Application configuration shared by all applications acceptance tests
+ */
+return [
+    'components' => [
+        'db' => [
+            'dsn' => 'mysql:host=localhost;dbname=yii2_advanced_acceptance',
+        ],
+    ],
+];
\ No newline at end of file
diff --git a/apps/advanced/tests/codeception/backend/acceptance/_config.php b/apps/advanced/tests/codeception/config/backend/acceptance.php
similarity index 65%
rename from apps/advanced/tests/codeception/backend/acceptance/_config.php
rename to apps/advanced/tests/codeception/config/backend/acceptance.php
index 92fab0a123..63f5af5b66 100644
--- a/apps/advanced/tests/codeception/backend/acceptance/_config.php
+++ b/apps/advanced/tests/codeception/config/backend/acceptance.php
@@ -1,16 +1,13 @@
 <?php
 defined('ROOT_DIR') or define('ROOT_DIR', dirname(dirname(dirname(dirname(__DIR__)))));
 return yii\helpers\ArrayHelper::merge(
-    require(ROOT_DIR . '/backend/config/main.php'),
-    require(ROOT_DIR . '/backend/config/main-local.php'),
     require(ROOT_DIR . '/common/config/main.php'),
     require(ROOT_DIR . '/common/config/main-local.php'),
-    require(__DIR__ . '/../_config.php'),
+    require(ROOT_DIR . '/backend/config/main.php'),
+    require(ROOT_DIR . '/backend/config/main-local.php'),
+    require(dirname(__DIR__) . '/config.php'),
+    require(dirname(__DIR__) . '/acceptance.php'),
+    require(__DIR__ . '/config.php'),
     [
-        'components' => [
-            'db' => [
-                'dsn' => 'mysql:host=localhost;dbname=yii2_advanced_acceptance',
-            ],
-        ],
     ]
 );
diff --git a/apps/advanced/tests/codeception/config/backend/config.php b/apps/advanced/tests/codeception/config/backend/config.php
new file mode 100644
index 0000000000..a1b26e621a
--- /dev/null
+++ b/apps/advanced/tests/codeception/config/backend/config.php
@@ -0,0 +1,2 @@
+<?php
+return [];
\ No newline at end of file
diff --git a/apps/advanced/tests/codeception/backend/functional/_config.php b/apps/advanced/tests/codeception/config/backend/functional.php
similarity index 65%
rename from apps/advanced/tests/codeception/backend/functional/_config.php
rename to apps/advanced/tests/codeception/config/backend/functional.php
index 6d4bf7cecb..cf55578f65 100644
--- a/apps/advanced/tests/codeception/backend/functional/_config.php
+++ b/apps/advanced/tests/codeception/config/backend/functional.php
@@ -7,12 +7,9 @@ return yii\helpers\ArrayHelper::merge(
     require(ROOT_DIR . '/backend/config/main-local.php'),
     require(ROOT_DIR . '/common/config/main.php'),
     require(ROOT_DIR . '/common/config/main-local.php'),
-    require(__DIR__ . '/../_config.php'),
+    require(dirname(__DIR__) . '/config.php'),
+    require(dirname(__DIR__) . '/functional.php'),
+    require(__DIR__ . '/config.php'),
     [
-        'components' => [
-            'db' => [
-                'dsn' => 'mysql:host=localhost;dbname=yii2_advanced_functional',
-            ],
-        ],
     ]
 );
diff --git a/apps/advanced/tests/codeception/backend/unit/_config.php b/apps/advanced/tests/codeception/config/backend/unit.php
similarity index 58%
rename from apps/advanced/tests/codeception/backend/unit/_config.php
rename to apps/advanced/tests/codeception/config/backend/unit.php
index 6cf1d2e57a..6363e45d02 100644
--- a/apps/advanced/tests/codeception/backend/unit/_config.php
+++ b/apps/advanced/tests/codeception/config/backend/unit.php
@@ -5,12 +5,9 @@ return yii\helpers\ArrayHelper::merge(
     require(ROOT_DIR . '/common/config/main-local.php'),
     require(ROOT_DIR . '/backend/config/main.php'),
     require(ROOT_DIR . '/backend/config/main-local.php'),
-    require(dirname(__DIR__) . '/_config.php'),
+    require(dirname(__DIR__) . '/config.php'),
+    require(dirname(__DIR__) . '/unit.php'),
+    require(__DIR__ . '/config.php'),
     [
-        'components' => [
-            'db' => [
-                'dsn' => 'mysql:host=localhost;dbname=yii2_advanced_unit',
-            ],
-        ],
     ]
 );
diff --git a/apps/advanced/tests/codeception/common/unit/_config.php b/apps/advanced/tests/codeception/config/common/unit.php
similarity index 55%
rename from apps/advanced/tests/codeception/common/unit/_config.php
rename to apps/advanced/tests/codeception/config/common/unit.php
index 88a1bc5a18..3ada667117 100644
--- a/apps/advanced/tests/codeception/common/unit/_config.php
+++ b/apps/advanced/tests/codeception/config/common/unit.php
@@ -1,15 +1,13 @@
 <?php
-
+/**
+ * Application config for common unit tests
+ */
 return yii\helpers\ArrayHelper::merge(
     require(ROOT_DIR . '/common/config/main.php'),
     require(ROOT_DIR . '/common/config/main-local.php'),
-    require(__DIR__ . '/../_config.php'),
+    require(dirname(__DIR__) . '/config.php'),
+    require(dirname(__DIR__) . '/unit.php'),
     [
-        'components' => [
-            'db' => [
-                'dsn' => 'mysql:host=localhost;dbname=yii2_advanced_unit',
-            ],
-        ],
         'id' => 'app-common',
         'basePath' => dirname(__DIR__),
     ]
diff --git a/apps/advanced/tests/codeception/common/_config.php b/apps/advanced/tests/codeception/config/config.php
similarity index 74%
rename from apps/advanced/tests/codeception/common/_config.php
rename to apps/advanced/tests/codeception/config/config.php
index 8629dd0d99..b6df8d2ea3 100644
--- a/apps/advanced/tests/codeception/common/_config.php
+++ b/apps/advanced/tests/codeception/config/config.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * application configurations shared by all test types
+ * Application configuration shared by all applications and test types
  */
 return [
     'components' => [
diff --git a/apps/advanced/tests/codeception/config/console/unit.php b/apps/advanced/tests/codeception/config/console/unit.php
new file mode 100644
index 0000000000..661596cc6b
--- /dev/null
+++ b/apps/advanced/tests/codeception/config/console/unit.php
@@ -0,0 +1,12 @@
+<?php
+
+return yii\helpers\ArrayHelper::merge(
+    require(ROOT_DIR . '/common/config/main.php'),
+    require(ROOT_DIR . '/common/config/main-local.php'),
+    require(ROOT_DIR . '/console/config/main.php'),
+    require(ROOT_DIR . '/console/config/main-local.php'),
+    require(dirname(__DIR__) . '/config.php'),
+    require(dirname(__DIR__) . '/unit.php'),
+    [
+    ]
+);
diff --git a/apps/advanced/tests/codeception/frontend/acceptance/_config.php b/apps/advanced/tests/codeception/config/frontend/acceptance.php
similarity index 65%
rename from apps/advanced/tests/codeception/frontend/acceptance/_config.php
rename to apps/advanced/tests/codeception/config/frontend/acceptance.php
index 0781a3d40a..95086a67aa 100644
--- a/apps/advanced/tests/codeception/frontend/acceptance/_config.php
+++ b/apps/advanced/tests/codeception/config/frontend/acceptance.php
@@ -1,16 +1,13 @@
 <?php
 defined('ROOT_DIR') or define('ROOT_DIR', dirname(dirname(dirname(dirname(__DIR__)))));
 return yii\helpers\ArrayHelper::merge(
-    require(ROOT_DIR . '/frontend/config/main.php'),
-    require(ROOT_DIR . '/frontend/config/main-local.php'),
     require(ROOT_DIR . '/common/config/main.php'),
     require(ROOT_DIR . '/common/config/main-local.php'),
-    require(__DIR__ . '/../_config.php'),
+    require(ROOT_DIR . '/frontend/config/main.php'),
+    require(ROOT_DIR . '/frontend/config/main-local.php'),
+    require(dirname(__DIR__) . '/config.php'),
+    require(dirname(__DIR__) . '/acceptance.php'),
+    require(__DIR__ . '/config.php'),
     [
-        'components' => [
-            'db' => [
-                'dsn' => 'mysql:host=localhost;dbname=yii2_advanced_acceptance',
-            ],
-        ],
     ]
 );
diff --git a/apps/advanced/tests/codeception/config/frontend/config.php b/apps/advanced/tests/codeception/config/frontend/config.php
new file mode 100644
index 0000000000..a1b26e621a
--- /dev/null
+++ b/apps/advanced/tests/codeception/config/frontend/config.php
@@ -0,0 +1,2 @@
+<?php
+return [];
\ No newline at end of file
diff --git a/apps/advanced/tests/codeception/frontend/functional/_config.php b/apps/advanced/tests/codeception/config/frontend/functional.php
similarity index 65%
rename from apps/advanced/tests/codeception/frontend/functional/_config.php
rename to apps/advanced/tests/codeception/config/frontend/functional.php
index 036926faf5..0230b899ef 100644
--- a/apps/advanced/tests/codeception/frontend/functional/_config.php
+++ b/apps/advanced/tests/codeception/config/frontend/functional.php
@@ -3,16 +3,13 @@ $_SERVER['SCRIPT_FILENAME'] = FRONTEND_ENTRY_FILE;
 $_SERVER['SCRIPT_NAME'] = FRONTEND_ENTRY_URL;
 
 return yii\helpers\ArrayHelper::merge(
-    require(ROOT_DIR . '/frontend/config/main.php'),
-    require(ROOT_DIR . '/frontend/config/main-local.php'),
     require(ROOT_DIR . '/common/config/main.php'),
     require(ROOT_DIR . '/common/config/main-local.php'),
-    require(__DIR__ . '/../_config.php'),
+    require(ROOT_DIR . '/frontend/config/main.php'),
+    require(ROOT_DIR . '/frontend/config/main-local.php'),
+    require(dirname(__DIR__) . '/config.php'),
+    require(dirname(__DIR__) . '/functional.php'),
+    require(__DIR__ . '/config.php'),
     [
-        'components' => [
-            'db' => [
-                'dsn' => 'mysql:host=localhost;dbname=yii2_advanced_functional',
-            ],
-        ],
     ]
 );
diff --git a/apps/advanced/tests/codeception/frontend/unit/_config.php b/apps/advanced/tests/codeception/config/frontend/unit.php
similarity index 59%
rename from apps/advanced/tests/codeception/frontend/unit/_config.php
rename to apps/advanced/tests/codeception/config/frontend/unit.php
index a34a67b89a..da0adec895 100644
--- a/apps/advanced/tests/codeception/frontend/unit/_config.php
+++ b/apps/advanced/tests/codeception/config/frontend/unit.php
@@ -5,12 +5,9 @@ return yii\helpers\ArrayHelper::merge(
     require(ROOT_DIR . '/common/config/main-local.php'),
     require(ROOT_DIR . '/frontend/config/main.php'),
     require(ROOT_DIR . '/frontend/config/main-local.php'),
-    require(__DIR__ . '/../_config.php'),
+    require(dirname(__DIR__) . '/config.php'),
+    require(dirname(__DIR__) . '/unit.php'),
+    require(__DIR__ . '/config.php'),
     [
-        'components' => [
-            'db' => [
-                'dsn' => 'mysql:host=localhost;dbname=yii2_advanced_unit',
-            ],
-        ],
     ]
 );
diff --git a/apps/advanced/tests/codeception/config/functional.php b/apps/advanced/tests/codeception/config/functional.php
new file mode 100644
index 0000000000..290f5f6d6f
--- /dev/null
+++ b/apps/advanced/tests/codeception/config/functional.php
@@ -0,0 +1,11 @@
+<?php
+/**
+ * Application configuration shared by all applications functional tests
+ */
+return [
+    'components' => [
+        'db' => [
+            'dsn' => 'mysql:host=localhost;dbname=yii2_advanced_acceptance',
+        ],
+    ],
+];
\ No newline at end of file
diff --git a/apps/advanced/tests/codeception/config/unit.php b/apps/advanced/tests/codeception/config/unit.php
new file mode 100644
index 0000000000..26abe6bd23
--- /dev/null
+++ b/apps/advanced/tests/codeception/config/unit.php
@@ -0,0 +1,11 @@
+<?php
+/**
+ * Application configuration shared by all applications unit tests
+ */
+return [
+    'components' => [
+        'db' => [
+            'dsn' => 'mysql:host=localhost;dbname=yii2_advanced_unit',
+        ],
+    ],
+];
\ No newline at end of file
diff --git a/apps/advanced/tests/codeception/console/_config.php b/apps/advanced/tests/codeception/console/_config.php
deleted file mode 100644
index 8629dd0d99..0000000000
--- a/apps/advanced/tests/codeception/console/_config.php
+++ /dev/null
@@ -1,14 +0,0 @@
-<?php
-/**
- * application configurations shared by all test types
- */
-return [
-    'components' => [
-        'mailer' => [
-            'useFileTransport' => true,
-        ],
-        'urlManager' => [
-            'showScriptName' => true,
-        ],
-    ],
-];
diff --git a/apps/advanced/tests/codeception/console/unit/DbTestCase.php b/apps/advanced/tests/codeception/console/unit/DbTestCase.php
index 28c90a6f75..0d8e56e8b6 100644
--- a/apps/advanced/tests/codeception/console/unit/DbTestCase.php
+++ b/apps/advanced/tests/codeception/console/unit/DbTestCase.php
@@ -7,5 +7,5 @@ namespace console\tests\unit;
  */
 class DbTestCase extends \yii\codeception\DbTestCase
 {
-    public $appConfig = '@console/tests/unit/_config.php';
+    public $appConfig = '@codeception/config/console/config.php';
 }
diff --git a/apps/advanced/tests/codeception/console/unit/TestCase.php b/apps/advanced/tests/codeception/console/unit/TestCase.php
index 7af86c36de..8bfc7adf54 100644
--- a/apps/advanced/tests/codeception/console/unit/TestCase.php
+++ b/apps/advanced/tests/codeception/console/unit/TestCase.php
@@ -7,5 +7,5 @@ namespace console\tests\unit;
  */
 class TestCase extends \yii\codeception\TestCase
 {
-    public $appConfig = '@console/tests/unit/_config.php';
+    public $appConfig = '@codeception/config/console/config.php';
 }
diff --git a/apps/advanced/tests/codeception/console/unit/_config.php b/apps/advanced/tests/codeception/console/unit/_config.php
deleted file mode 100644
index 97ed57b0f2..0000000000
--- a/apps/advanced/tests/codeception/console/unit/_config.php
+++ /dev/null
@@ -1,16 +0,0 @@
-<?php
-
-return yii\helpers\ArrayHelper::merge(
-    require(__DIR__ . '/../../../common/config/main.php'),
-    require(__DIR__ . '/../../../common/config/main-local.php'),
-    require(__DIR__ . '/../../config/main.php'),
-    require(__DIR__ . '/../../config/main-local.php'),
-    require(__DIR__ . '/../_config.php'),
-    [
-        'components' => [
-            'db' => [
-                'dsn' => 'mysql:host=localhost;dbname=yii2_advanced_unit',
-            ],
-        ],
-    ]
-);
diff --git a/apps/advanced/tests/codeception/frontend/_config.php b/apps/advanced/tests/codeception/frontend/_config.php
deleted file mode 100644
index 8629dd0d99..0000000000
--- a/apps/advanced/tests/codeception/frontend/_config.php
+++ /dev/null
@@ -1,14 +0,0 @@
-<?php
-/**
- * application configurations shared by all test types
- */
-return [
-    'components' => [
-        'mailer' => [
-            'useFileTransport' => true,
-        ],
-        'urlManager' => [
-            'showScriptName' => true,
-        ],
-    ],
-];
diff --git a/apps/advanced/tests/codeception/frontend/acceptance/_bootstrap.php b/apps/advanced/tests/codeception/frontend/acceptance/_bootstrap.php
index 6ce3d175be..b0a40eff2c 100644
--- a/apps/advanced/tests/codeception/frontend/acceptance/_bootstrap.php
+++ b/apps/advanced/tests/codeception/frontend/acceptance/_bootstrap.php
@@ -1,3 +1,2 @@
 <?php
-
-new yii\web\Application(require(__DIR__ . '/_config.php'));
+new yii\web\Application(require(dirname(dirname(__DIR__)) . '/config/frontend/acceptance.php'));
diff --git a/apps/advanced/tests/codeception/frontend/functional.suite.yml b/apps/advanced/tests/codeception/frontend/functional.suite.yml
index b04e7c8b9c..632ed37bed 100644
--- a/apps/advanced/tests/codeception/frontend/functional.suite.yml
+++ b/apps/advanced/tests/codeception/frontend/functional.suite.yml
@@ -14,4 +14,4 @@ modules:
       - codeception\common\_support\FixtureHelper
     config:
         Yii2:
-            configFile: 'functional/_config.php'
+            configFile: '../config/frontend/functional.php'
diff --git a/apps/advanced/tests/codeception/frontend/functional/_bootstrap.php b/apps/advanced/tests/codeception/frontend/functional/_bootstrap.php
index 6ce3d175be..1abc491110 100644
--- a/apps/advanced/tests/codeception/frontend/functional/_bootstrap.php
+++ b/apps/advanced/tests/codeception/frontend/functional/_bootstrap.php
@@ -1,3 +1,3 @@
 <?php
 
-new yii\web\Application(require(__DIR__ . '/_config.php'));
+new yii\web\Application(require(dirname(dirname(__DIR__)) . '/config/frontend/functional.php'));
diff --git a/apps/advanced/tests/codeception/frontend/unit/DbTestCase.php b/apps/advanced/tests/codeception/frontend/unit/DbTestCase.php
index 1111f78a93..70b350c628 100644
--- a/apps/advanced/tests/codeception/frontend/unit/DbTestCase.php
+++ b/apps/advanced/tests/codeception/frontend/unit/DbTestCase.php
@@ -7,5 +7,5 @@ namespace codeception\frontend\unit;
  */
 class DbTestCase extends \yii\codeception\DbTestCase
 {
-    public $appConfig = '@codeception/frontend/unit/_config.php';
+    public $appConfig = '@codeception/config/frontend/unit.php';
 }
diff --git a/apps/advanced/tests/codeception/frontend/unit/TestCase.php b/apps/advanced/tests/codeception/frontend/unit/TestCase.php
index 0da48dd063..1a0c659093 100644
--- a/apps/advanced/tests/codeception/frontend/unit/TestCase.php
+++ b/apps/advanced/tests/codeception/frontend/unit/TestCase.php
@@ -7,5 +7,5 @@ namespace codeception\frontend\unit;
  */
 class TestCase extends \yii\codeception\TestCase
 {
-    public $appConfig = '@codeception/frontend/unit/_config.php';
+    public $appConfig = '@codeception/config/frontend/unit.php';
 }
diff --git a/apps/basic/tests/codeception/_config.php b/apps/basic/tests/codeception/_config.php
deleted file mode 100644
index 8629dd0d99..0000000000
--- a/apps/basic/tests/codeception/_config.php
+++ /dev/null
@@ -1,14 +0,0 @@
-<?php
-/**
- * application configurations shared by all test types
- */
-return [
-    'components' => [
-        'mailer' => [
-            'useFileTransport' => true,
-        ],
-        'urlManager' => [
-            'showScriptName' => true,
-        ],
-    ],
-];
diff --git a/apps/basic/tests/codeception/acceptance/ContactCept.php b/apps/basic/tests/codeception/acceptance/ContactCept.php
index 27858f8e90..c9adc7e15e 100644
--- a/apps/basic/tests/codeception/acceptance/ContactCept.php
+++ b/apps/basic/tests/codeception/acceptance/ContactCept.php
@@ -21,11 +21,11 @@ $I->see('The verification code is incorrect');
 
 $I->amGoingTo('submit contact form with not correct email');
 $contactPage->submit([
-    'name'			=>	'tester',
-    'email'			=>	'tester.email',
-    'subject'		=>	'test subject',
-    'body'			=>	'test content',
-    'verifyCode'	=>	'testme',
+    'name' => 'tester',
+    'email' => 'tester.email',
+    'subject' => 'test subject',
+    'body' => 'test content',
+    'verifyCode' => 'testme',
 ]);
 $I->expectTo('see that email adress is wrong');
 $I->dontSee('Name cannot be blank', '.help-inline');
@@ -36,11 +36,11 @@ $I->dontSee('The verification code is incorrect', '.help-inline');
 
 $I->amGoingTo('submit contact form with correct data');
 $contactPage->submit([
-    'name'			=>	'tester',
-    'email'			=>	'tester@example.com',
-    'subject'		=>	'test subject',
-    'body'			=>	'test content',
-    'verifyCode'	=>	'testme',
+    'name' => 'tester',
+    'email' => 'tester@example.com',
+    'subject' => 'test subject',
+    'body' => 'test content',
+    'verifyCode' => 'testme',
 ]);
 if (method_exists($I, 'wait')) {
     $I->wait(3); // only for selenium
diff --git a/apps/basic/tests/codeception/acceptance/_bootstrap.php b/apps/basic/tests/codeception/acceptance/_bootstrap.php
index 6ce3d175be..36f9f1d113 100644
--- a/apps/basic/tests/codeception/acceptance/_bootstrap.php
+++ b/apps/basic/tests/codeception/acceptance/_bootstrap.php
@@ -1,3 +1,2 @@
 <?php
-
-new yii\web\Application(require(__DIR__ . '/_config.php'));
+new yii\web\Application(require(dirname(__DIR__) . '/config/acceptance.php'));
diff --git a/apps/basic/tests/codeception/bin/_console_bootstrap.php b/apps/basic/tests/codeception/bin/_bootstrap.php
similarity index 99%
rename from apps/basic/tests/codeception/bin/_console_bootstrap.php
rename to apps/basic/tests/codeception/bin/_bootstrap.php
index eff8b403fe..fcff154115 100644
--- a/apps/basic/tests/codeception/bin/_console_bootstrap.php
+++ b/apps/basic/tests/codeception/bin/_bootstrap.php
@@ -1,7 +1,5 @@
 <?php
-
 defined('YII_DEBUG') or define('YII_DEBUG', true);
-
 defined('YII_ENV') or define('YII_ENV', 'test');
 
 // fcgi doesn't have STDIN and STDOUT defined by default
diff --git a/apps/basic/tests/codeception/bin/yii_acceptance b/apps/basic/tests/codeception/bin/yii_acceptance
index a02d9daf1f..89a6e3c3e6 100644
--- a/apps/basic/tests/codeception/bin/yii_acceptance
+++ b/apps/basic/tests/codeception/bin/yii_acceptance
@@ -8,11 +8,11 @@
  * @license http://www.yiiframework.com/license/
  */
 
-require_once __DIR__ . '/_console_bootstrap.php';
+require_once __DIR__ . '/_bootstrap.php';
 
 $config = yii\helpers\ArrayHelper::merge(
     require(ROOT_DIR . '/config/console.php'),
-    require(__DIR__ . '/../_config.php'),
+    require(__DIR__ . '/../config/config.php'),
     [
         'components' => [
             'db' => [
diff --git a/apps/basic/tests/codeception/bin/yii_functional b/apps/basic/tests/codeception/bin/yii_functional
index 44051e2caf..148420fe00 100644
--- a/apps/basic/tests/codeception/bin/yii_functional
+++ b/apps/basic/tests/codeception/bin/yii_functional
@@ -8,11 +8,11 @@
  * @license http://www.yiiframework.com/license/
  */
 
-require_once __DIR__ . '/_console_bootstrap.php';
+require_once __DIR__ . '/_bootstrap.php';
 
 $config = yii\helpers\ArrayHelper::merge(
     require(ROOT_DIR . '/config/console.php'),
-    require(__DIR__ . '/../_config.php'),
+    require(__DIR__ . '/../config/config.php'),
     [
         'components' => [
             'db' => [
diff --git a/apps/basic/tests/codeception/bin/yii_unit b/apps/basic/tests/codeception/bin/yii_unit
index e9b799903d..5fb938e517 100644
--- a/apps/basic/tests/codeception/bin/yii_unit
+++ b/apps/basic/tests/codeception/bin/yii_unit
@@ -8,11 +8,11 @@
  * @license http://www.yiiframework.com/license/
  */
 
-require_once __DIR__ . '/_console_bootstrap.php';
+require_once __DIR__ . '/_bootstrap.php';
 
 $config = yii\helpers\ArrayHelper::merge(
     require(ROOT_DIR . '/config/console.php'),
-    require(__DIR__ . '/../_config.php'),
+    require(__DIR__ . '/../config/config.php'),
     [
         'components' => [
             'db' => [
diff --git a/apps/basic/tests/codeception/acceptance/_config.php b/apps/basic/tests/codeception/config/acceptance.php
similarity index 73%
rename from apps/basic/tests/codeception/acceptance/_config.php
rename to apps/basic/tests/codeception/config/acceptance.php
index d620a7d9e9..c80d4687ac 100644
--- a/apps/basic/tests/codeception/acceptance/_config.php
+++ b/apps/basic/tests/codeception/config/acceptance.php
@@ -1,8 +1,10 @@
 <?php
-
+/**
+ * Application configuration for acceptance tests
+ */
 return yii\helpers\ArrayHelper::merge(
     require(__DIR__ . '/../../../config/web.php'),
-    require(__DIR__ . '/../_config.php'),
+    require(__DIR__ . '/config.php'),
     [
         'components' => [
             'db' => [
diff --git a/apps/advanced/tests/codeception/backend/_config.php b/apps/basic/tests/codeception/config/config.php
similarity index 78%
rename from apps/advanced/tests/codeception/backend/_config.php
rename to apps/basic/tests/codeception/config/config.php
index 8629dd0d99..005d365c4a 100644
--- a/apps/advanced/tests/codeception/backend/_config.php
+++ b/apps/basic/tests/codeception/config/config.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * application configurations shared by all test types
+ * Application configuration shared by all test types
  */
 return [
     'components' => [
diff --git a/apps/basic/tests/codeception/functional/_config.php b/apps/basic/tests/codeception/config/functional.php
similarity index 78%
rename from apps/basic/tests/codeception/functional/_config.php
rename to apps/basic/tests/codeception/config/functional.php
index 515c90487b..13cfc64582 100644
--- a/apps/basic/tests/codeception/functional/_config.php
+++ b/apps/basic/tests/codeception/config/functional.php
@@ -2,9 +2,12 @@
 $_SERVER['SCRIPT_FILENAME'] = TEST_ENTRY_FILE;
 $_SERVER['SCRIPT_NAME'] = TEST_ENTRY_URL;
 
+/**
+ * Application configuration for functional tests
+ */
 return yii\helpers\ArrayHelper::merge(
     require(__DIR__ . '/../../../config/web.php'),
-    require(__DIR__ . '/../_config.php'),
+    require(__DIR__ . '/config.php'),
     [
         'components' => [
             'db' => [
diff --git a/apps/basic/tests/codeception/unit/_config.php b/apps/basic/tests/codeception/config/unit.php
similarity index 74%
rename from apps/basic/tests/codeception/unit/_config.php
rename to apps/basic/tests/codeception/config/unit.php
index 36b0114469..1b8772d5b4 100644
--- a/apps/basic/tests/codeception/unit/_config.php
+++ b/apps/basic/tests/codeception/config/unit.php
@@ -1,8 +1,10 @@
 <?php
-
+/**
+ * Application configuration for unit tests
+ */
 return yii\helpers\ArrayHelper::merge(
     require(__DIR__ . '/../../../config/web.php'),
-    require(__DIR__ . '/../_config.php'),
+    require(__DIR__ . '/config.php'),
     [
         'components' => [
             'db' => [
diff --git a/apps/basic/tests/codeception/functional.suite.yml b/apps/basic/tests/codeception/functional.suite.yml
index 94ff0c9767..ad7164cb66 100644
--- a/apps/basic/tests/codeception/functional.suite.yml
+++ b/apps/basic/tests/codeception/functional.suite.yml
@@ -13,4 +13,4 @@ modules:
       - Yii2
     config:
         Yii2:
-            configFile: 'codeception/functional/_config.php'
+            configFile: 'codeception/config/functional.php'
diff --git a/apps/basic/tests/codeception/functional/_bootstrap.php b/apps/basic/tests/codeception/functional/_bootstrap.php
index 6ce3d175be..8aac0915b2 100644
--- a/apps/basic/tests/codeception/functional/_bootstrap.php
+++ b/apps/basic/tests/codeception/functional/_bootstrap.php
@@ -1,3 +1,2 @@
 <?php
-
-new yii\web\Application(require(__DIR__ . '/_config.php'));
+new yii\web\Application(require(dirname(__DIR__) . '/config/functional.php'));
diff --git a/apps/basic/web/index-test.php b/apps/basic/web/index-test.php
index dd8a4965c2..32b4ce3e1e 100644
--- a/apps/basic/web/index-test.php
+++ b/apps/basic/web/index-test.php
@@ -11,6 +11,6 @@ defined('YII_ENV') or define('YII_ENV', 'test');
 require(__DIR__ . '/../vendor/autoload.php');
 require(__DIR__ . '/../vendor/yiisoft/yii2/Yii.php');
 
-$config = require(__DIR__ . '/../tests/codeception/acceptance/_config.php');
+$config = require(__DIR__ . '/../tests/codeception/config/acceptance.php');
 
 (new yii\web\Application($config))->run();
diff --git a/extensions/codeception/TestCase.php b/extensions/codeception/TestCase.php
index c6f31073e4..1d331d82a4 100644
--- a/extensions/codeception/TestCase.php
+++ b/extensions/codeception/TestCase.php
@@ -31,7 +31,7 @@ class TestCase extends Test
      * The application configuration array may contain an optional `class` element which specifies the class
      * name of the application instance to be created. By default, a [[\yii\web\Application]] instance will be created.
      */
-    public $appConfig = '@codeception/unit/_config.php';
+    public $appConfig = '@codeception/config/unit.php';
 
 
     /**