diff --git a/.travis.yml b/.travis.yml
index aa4b850..4583c1b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,10 +8,6 @@ matrix:
     - php: "7.1"
     - php: "7.0"
     - php: "5.6"
-    - php: "5.5"
-      dist: trusty
-    - php: "5.4"
-      dist: trusty
 
 # faster builds on new travis setup not using sudo
 sudo: false
diff --git a/codeception.yml b/codeception.yml
index a95affe..d5aecb3 100644
--- a/codeception.yml
+++ b/codeception.yml
@@ -1,11 +1,11 @@
 actor: Tester
+bootstrap: _bootstrap.php
 paths:
     tests: tests
     log: tests/_output
     data: tests/_data
     helpers: tests/_support
 settings:
-    bootstrap: _bootstrap.php
     memory_limit: 1024M
     colors: true
 modules:
diff --git a/composer.json b/composer.json
index 8ffc76d..324bd02 100644
--- a/composer.json
+++ b/composer.json
@@ -23,11 +23,13 @@
         "yiisoft/yii2-debug": "~2.1.0",
         "yiisoft/yii2-gii": "~2.1.0",
         "yiisoft/yii2-faker": "~2.0.0",
-
-        "codeception/base": "~2.3.0",
-        "codeception/verify": "~0.4.0",
+        "codeception/codeception": "4.0.x-dev | ^4.0",
+        "codeception/verify": "~0.5.0 || ~1.1.0",
         "codeception/specify": "~0.4.6",
-        "symfony/browser-kit": ">=2.7 <=4.2.4"
+        "symfony/browser-kit": ">=2.7 <=4.2.4",
+        "codeception/module-filesystem": "^1.0.0",
+        "codeception/module-yii2": "^1.0.0",
+        "codeception/module-asserts": "^1.0.0"
     },
     "config": {
         "process-timeout": 1800,
diff --git a/tests/unit/models/ContactFormTest.php b/tests/unit/models/ContactFormTest.php
index 031d2bd..0744487 100644
--- a/tests/unit/models/ContactFormTest.php
+++ b/tests/unit/models/ContactFormTest.php
@@ -43,6 +43,6 @@ class ContactFormTest extends \Codeception\Test\Unit
         expect($emailMessage->getFrom())->hasKey('noreply@example.com');
         expect($emailMessage->getReplyTo())->hasKey('tester@example.com');
         expect($emailMessage->getSubject())->equals('very important letter subject');
-        expect($emailMessage->toString())->contains('body of current message');
+        expect($emailMessage->toString())->stringContainsString('body of current message');
     }
 }