diff --git a/src/Codeception/Lib/Connector/Yii2.php b/src/Codeception/Lib/Connector/Yii2.php
index 1a76275..890ab45 100644
--- a/src/Codeception/Lib/Connector/Yii2.php
+++ b/src/Codeception/Lib/Connector/Yii2.php
@@ -1,4 +1,7 @@
 <?php
+
+declare(strict_types=1);
+
 namespace Codeception\Lib\Connector;
 
 use Codeception\Exception\ConfigurationException;
@@ -402,10 +405,11 @@ protected function encodeCookies(
                     : $cookie->value;
                 $value = $security->hashData(serialize($data), $validationKey);
             }
+            $expires = is_int($cookie->expire) ? (string)$cookie->expire : null;
             $c = new Cookie(
                 $cookie->name,
                 $value,
-                $cookie->expire,
+                $expires,
                 $cookie->path,
                 $cookie->domain,
                 $cookie->secure,
diff --git a/src/Codeception/Lib/Connector/Yii2/ConnectionWatcher.php b/src/Codeception/Lib/Connector/Yii2/ConnectionWatcher.php
index 291c921..aa92f7f 100644
--- a/src/Codeception/Lib/Connector/Yii2/ConnectionWatcher.php
+++ b/src/Codeception/Lib/Connector/Yii2/ConnectionWatcher.php
@@ -1,5 +1,6 @@
 <?php
 
+declare(strict_types=1);
 
 namespace Codeception\Lib\Connector\Yii2;
 
diff --git a/src/Codeception/Lib/Connector/Yii2/FixturesStore.php b/src/Codeception/Lib/Connector/Yii2/FixturesStore.php
index 0729fec..71c490e 100644
--- a/src/Codeception/Lib/Connector/Yii2/FixturesStore.php
+++ b/src/Codeception/Lib/Connector/Yii2/FixturesStore.php
@@ -1,4 +1,7 @@
 <?php
+
+declare(strict_types=1);
+
 namespace Codeception\Lib\Connector\Yii2;
 
 use yii\test\FixtureTrait;
diff --git a/src/Codeception/Lib/Connector/Yii2/Logger.php b/src/Codeception/Lib/Connector/Yii2/Logger.php
index b229f32..0a2501f 100644
--- a/src/Codeception/Lib/Connector/Yii2/Logger.php
+++ b/src/Codeception/Lib/Connector/Yii2/Logger.php
@@ -1,4 +1,7 @@
 <?php
+
+declare(strict_types=1);
+
 namespace Codeception\Lib\Connector\Yii2;
 
 use Codeception\Util\Debug;
diff --git a/src/Codeception/Lib/Connector/Yii2/TestMailer.php b/src/Codeception/Lib/Connector/Yii2/TestMailer.php
index 16e254d..c6276a4 100644
--- a/src/Codeception/Lib/Connector/Yii2/TestMailer.php
+++ b/src/Codeception/Lib/Connector/Yii2/TestMailer.php
@@ -1,4 +1,7 @@
 <?php
+
+declare(strict_types=1);
+
 namespace Codeception\Lib\Connector\Yii2;
 
 use yii\mail\BaseMailer;
diff --git a/src/Codeception/Lib/Connector/Yii2/TransactionForcer.php b/src/Codeception/Lib/Connector/Yii2/TransactionForcer.php
index fbc08f2..7c2588a 100644
--- a/src/Codeception/Lib/Connector/Yii2/TransactionForcer.php
+++ b/src/Codeception/Lib/Connector/Yii2/TransactionForcer.php
@@ -1,5 +1,6 @@
 <?php
 
+declare(strict_types=1);
 
 namespace Codeception\Lib\Connector\Yii2;
 
diff --git a/src/Codeception/Module/Yii2.php b/src/Codeception/Module/Yii2.php
index 88b382b..99a3a2d 100644
--- a/src/Codeception/Module/Yii2.php
+++ b/src/Codeception/Module/Yii2.php
@@ -1,4 +1,7 @@
 <?php
+
+declare(strict_types=1);
+
 namespace Codeception\Module;
 
 use Codeception\Exception\ConfigurationException;
@@ -735,7 +738,7 @@ public function seeEmailIsSent(?int $num = null): void
             $this->assertNotEmpty($this->grabSentEmails(), 'emails were sent');
             return;
         }
-        $this->assertEquals($num, count($this->grabSentEmails()), 'number of sent emails is equal to ' . $num);
+        $this->assertSame($num, count($this->grabSentEmails()), 'number of sent emails is equal to ' . $num);
     }
 
     /**
@@ -757,7 +760,7 @@ public function dontSeeEmailIsSent(): void
      * <?php
      * $I->seeEmailIsSent();
      * $messages = $I->grabSentEmails();
-     * $I->assertEquals('admin@site,com', $messages[0]->getTo());
+     * $I->assertSame('admin@site,com', $messages[0]->getTo());
      * ```
      *
      * @part email
@@ -780,7 +783,7 @@ public function grabSentEmails(): array
      * <?php
      * $I->seeEmailIsSent();
      * $message = $I->grabLastSentEmail();
-     * $I->assertEquals('admin@site,com', $message->getTo());
+     * $I->assertSame('admin@site,com', $message->getTo());
      * ```
      * @part email
      */
diff --git a/tests/cases/closeConnections/fixtures/EmptyFixture.php b/tests/cases/closeConnections/fixtures/EmptyFixture.php
index c8aeae6..9006bb0 100644
--- a/tests/cases/closeConnections/fixtures/EmptyFixture.php
+++ b/tests/cases/closeConnections/fixtures/EmptyFixture.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\fixtures;
 
 use yii\test\DbFixture;
diff --git a/tests/cases/closeConnections/functional/FixturesCest.php b/tests/cases/closeConnections/functional/FixturesCest.php
index 1dea8f4..1c034cf 100644
--- a/tests/cases/closeConnections/functional/FixturesCest.php
+++ b/tests/cases/closeConnections/functional/FixturesCest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\closeConnections;
 
 use Codeception\Example;
@@ -29,7 +31,7 @@ protected function numberProvider()
      */
     public function NoConnections(FunctionalTester $I, Example $example)
     {
-        $I->assertEquals(SqlliteHelper::connectionCount(), $example['count']);
+        $I->assertSame(SqlliteHelper::connectionCount(), $example['count']);
     }
 
 }
\ No newline at end of file
diff --git a/tests/cases/closeConnections/functional/FixturesInBeforeCest.php b/tests/cases/closeConnections/functional/FixturesInBeforeCest.php
index 21de51d..711d587 100644
--- a/tests/cases/closeConnections/functional/FixturesInBeforeCest.php
+++ b/tests/cases/closeConnections/functional/FixturesInBeforeCest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\closeConnections;
 
 use Codeception\Example;
@@ -29,7 +31,7 @@ protected function numberProvider()
      */
     public function NoConnections(FunctionalTester $I, Example $example)
     {
-        $I->assertEquals(SqlliteHelper::connectionCount(), $example['count']);
+        $I->assertSame(SqlliteHelper::connectionCount(), $example['count']);
     }
 
 }
\ No newline at end of file
diff --git a/tests/cases/closeConnections/functional/NoFixturesCest.php b/tests/cases/closeConnections/functional/NoFixturesCest.php
index 245be50..2ff5b40 100644
--- a/tests/cases/closeConnections/functional/NoFixturesCest.php
+++ b/tests/cases/closeConnections/functional/NoFixturesCest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\closeConnections;
 
 use Codeception\Example;
@@ -20,6 +22,6 @@ protected function numberProvider()
      */
     public function NoConnections(FunctionalTester $I, Example $example)
     {
-        $I->assertEquals(SqlliteHelper::connectionCount(), $example['count']);
+        $I->assertSame(SqlliteHelper::connectionCount(), $example['count']);
     }
 }
\ No newline at end of file
diff --git a/tests/cases/closeConnections/helpers/SqlliteHelper.php b/tests/cases/closeConnections/helpers/SqlliteHelper.php
index cf8c460..15f263a 100644
--- a/tests/cases/closeConnections/helpers/SqlliteHelper.php
+++ b/tests/cases/closeConnections/helpers/SqlliteHelper.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\helpers;
 
 class SqlliteHelper
@@ -9,7 +11,7 @@ class SqlliteHelper
     public static function getTmpFile()
     {
         if (empty(self::$temp_name)) {
-            self::$temp_name = tempnam(null, '/file0');
+            self::$temp_name = tempnam('', '/file0');
         }
         return self::$temp_name;
     }
diff --git a/tests/cases/closeConnectionsNoCleanup/functional/FixturesCest.php b/tests/cases/closeConnectionsNoCleanup/functional/FixturesCest.php
index 025a423..92a5016 100644
--- a/tests/cases/closeConnectionsNoCleanup/functional/FixturesCest.php
+++ b/tests/cases/closeConnectionsNoCleanup/functional/FixturesCest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\closeConnectionsNoCleanup;
 
 use tests\FunctionalTester;
@@ -20,19 +22,19 @@ public function _fixtures()
     public function NoConnections1(FunctionalTester $I)
     {
         $count = SqlliteHelper::connectionCount();
-        $I->assertEquals(0, $count);
+        $I->assertSame(0, $count);
     }
 
     public function NoConnections2(FunctionalTester $I)
     {
         $count = SqlliteHelper::connectionCount();
-        $I->assertEquals(0, $count);
+        $I->assertSame(0, $count);
     }
 
     public function NoConnections3(FunctionalTester $I)
     {
         $count = SqlliteHelper::connectionCount();
-        $I->assertEquals(0, $count);
+        $I->assertSame(0, $count);
     }
 
 }
\ No newline at end of file
diff --git a/tests/cases/closeConnectionsNoCleanup/functional/FixturesInBeforeCest.php b/tests/cases/closeConnectionsNoCleanup/functional/FixturesInBeforeCest.php
index acf6031..bdf0241 100644
--- a/tests/cases/closeConnectionsNoCleanup/functional/FixturesInBeforeCest.php
+++ b/tests/cases/closeConnectionsNoCleanup/functional/FixturesInBeforeCest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\closeConnectionsNoCleanup;
 
 use tests\FunctionalTester;
@@ -20,18 +22,18 @@ public function _before(FunctionalTester $I)
     public function OnlyOneConnection1(FunctionalTester $I)
     {
         $count = SqlliteHelper::connectionCount();
-        $I->assertEquals(1, $count);
+        $I->assertSame(1, $count);
     }
 
     public function OnlyOneConnection2(FunctionalTester $I)
     {
         $count = SqlliteHelper::connectionCount();
-        $I->assertEquals(1, $count);
+        $I->assertSame(1, $count);
     }
 
     public function OnlyOneConnection3(FunctionalTester $I)
     {
         $count = SqlliteHelper::connectionCount();
-        $I->assertEquals(1, $count);
+        $I->assertSame(1, $count);
     }
 }
\ No newline at end of file
diff --git a/tests/cases/closeConnectionsNoCleanup/functional/ThirdCest.php b/tests/cases/closeConnectionsNoCleanup/functional/ThirdCest.php
index 0cbc42e..1a9caa2 100644
--- a/tests/cases/closeConnectionsNoCleanup/functional/ThirdCest.php
+++ b/tests/cases/closeConnectionsNoCleanup/functional/ThirdCest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\closeConnectionsNoCleanup;
 
 use tests\FunctionalTester;
@@ -11,7 +13,7 @@ class ThirdCest
     public function NoConnections1(FunctionalTester $I)
     {
         $count = SqlliteHelper::connectionCount();
-        $I->assertEquals(0, $count);
+        $I->assertSame(0, $count);
     }
 
     public function OnlyOneConnection2(FunctionalTester $I)
@@ -23,7 +25,7 @@ public function OnlyOneConnection2(FunctionalTester $I)
         ]);
 
         $count = SqlliteHelper::connectionCount();
-        $I->assertEquals(1, $count);
+        $I->assertSame(1, $count);
     }
 
     public function OnlyOneConnection3(FunctionalTester $I)
@@ -35,6 +37,6 @@ public function OnlyOneConnection3(FunctionalTester $I)
         ]);
 
         $count = SqlliteHelper::connectionCount();
-        $I->assertEquals(1, $count);
+        $I->assertSame(1, $count);
     }
 }
\ No newline at end of file
diff --git a/tests/cases/events/controllers/SiteController.php b/tests/cases/events/controllers/SiteController.php
index abcc66a..9c640e7 100644
--- a/tests/cases/events/controllers/SiteController.php
+++ b/tests/cases/events/controllers/SiteController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace app\controllers;
 use yii\web\Controller;
 
diff --git a/tests/cases/events/functional/ResponseCest.php b/tests/cases/events/functional/ResponseCest.php
index 30e7f37..360b888 100644
--- a/tests/cases/events/functional/ResponseCest.php
+++ b/tests/cases/events/functional/ResponseCest.php
@@ -1,4 +1,7 @@
 <?php
+
+declare(strict_types=1);
+
 namespace tests;
 
 use Codeception\Lib\Connector\Yii2;
@@ -18,11 +21,11 @@ public function testAfterSend(FunctionalTester $I)
         });
         $I->assertEmpty($sources);
         $I->amOnRoute('/');
-        $I->assertEquals(['config', 'bootstrap'], $sources);
+        $I->assertSame(['config', 'bootstrap'], $sources);
 
         $sources = [];
         $I->amOnRoute('/');
-        $I->assertEquals(['config', 'bootstrap'], $sources);
+        $I->assertSame(['config', 'bootstrap'], $sources);
 
     }
 
@@ -41,13 +44,13 @@ public function testAfterSendWithRecreate(FunctionalTester $I, \Codeception\Modu
         });
         $I->assertEmpty($sources);
         $I->amOnRoute('/');
-        $I->assertEquals(['config', 'bootstrap'], $sources);
+        $I->assertSame(['config', 'bootstrap'], $sources);
 
         $sources = [];
         $I->amOnRoute('/');
 
         // The module should fall back to the CLEAN_CLEAR method and keep event handlers intact.
-        $I->assertEquals(['config', 'bootstrap'], $sources);
+        $I->assertSame(['config', 'bootstrap'], $sources);
 
     }
 
@@ -70,14 +73,14 @@ public function testAfterSendWithForcedRecreate(FunctionalTester $I, \Codeceptio
 
         // We recreated the response component, since it has an event handler in its config
         // that event handler will still work.
-        $I->assertEquals(['config'], $sources);
+        $I->assertSame(['config'], $sources);
 
         $sources = [];
         $I->amOnRoute('/');
 
         // We recreated the response component, since it has an event handler in its config
         // that event handler will still work.
-        $I->assertEquals(['config'], $sources);
+        $I->assertSame(['config'], $sources);
 
     }
 }
\ No newline at end of file
diff --git a/tests/cases/locale-urls/controllers/SiteController.php b/tests/cases/locale-urls/controllers/SiteController.php
index d68f82a..c26c1bf 100644
--- a/tests/cases/locale-urls/controllers/SiteController.php
+++ b/tests/cases/locale-urls/controllers/SiteController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace app\localeurls\controllers;
 use yii\helpers\Url;
 use yii\web\Controller;
diff --git a/tests/cases/locale-urls/functional/LocaleUrlCest.php b/tests/cases/locale-urls/functional/LocaleUrlCest.php
index c9e7638..96c431a 100644
--- a/tests/cases/locale-urls/functional/LocaleUrlCest.php
+++ b/tests/cases/locale-urls/functional/LocaleUrlCest.php
@@ -1,4 +1,7 @@
 <?php
+
+declare(strict_types=1);
+
 namespace tests;
 
 use yii\web\Application;
diff --git a/tests/cases/mock-mailer/controllers/SiteController.php b/tests/cases/mock-mailer/controllers/SiteController.php
index 644557c..2aff2fc 100644
--- a/tests/cases/mock-mailer/controllers/SiteController.php
+++ b/tests/cases/mock-mailer/controllers/SiteController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace app\mockmailer\controllers;
 
 use yii\web\Controller;
diff --git a/tests/cases/mock-mailer/functional/MockMailerCest.php b/tests/cases/mock-mailer/functional/MockMailerCest.php
index fb61035..c1df829 100644
--- a/tests/cases/mock-mailer/functional/MockMailerCest.php
+++ b/tests/cases/mock-mailer/functional/MockMailerCest.php
@@ -1,4 +1,7 @@
 <?php
+
+declare(strict_types=1);
+
 namespace tests;
 
 use yii\web\Application;
diff --git a/tests/cases/pageCacheHeaderAlreadySent/controllers/UserController.php b/tests/cases/pageCacheHeaderAlreadySent/controllers/UserController.php
index ef8b022..35195eb 100644
--- a/tests/cases/pageCacheHeaderAlreadySent/controllers/UserController.php
+++ b/tests/cases/pageCacheHeaderAlreadySent/controllers/UserController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace app\pageCacheHeaderAlreadySent\controllers;
 
 use yii\filters\PageCache;
diff --git a/tests/cases/pageCacheHeaderAlreadySent/functional/PageCest.php b/tests/cases/pageCacheHeaderAlreadySent/functional/PageCest.php
index c2fa371..dda305f 100644
--- a/tests/cases/pageCacheHeaderAlreadySent/functional/PageCest.php
+++ b/tests/cases/pageCacheHeaderAlreadySent/functional/PageCest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 class PageCest {
 
     public function testCache(\tests\FunctionalTester $I)
diff --git a/tests/cases/simple/controllers/SiteController.php b/tests/cases/simple/controllers/SiteController.php
index 7d8a550..c8c02ef 100644
--- a/tests/cases/simple/controllers/SiteController.php
+++ b/tests/cases/simple/controllers/SiteController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace app\simple\controllers;
 use app\simple\helpers\EmptyString;
 use yii\base\Action;
diff --git a/tests/cases/simple/functional/SimpleCest.php b/tests/cases/simple/functional/SimpleCest.php
index b989325..7306fd7 100644
--- a/tests/cases/simple/functional/SimpleCest.php
+++ b/tests/cases/simple/functional/SimpleCest.php
@@ -1,4 +1,7 @@
 <?php
+
+declare(strict_types=1);
+
 namespace tests;
 
 use Codeception\Exception\ModuleException;
diff --git a/tests/cases/simple/helpers/DummyUser.php b/tests/cases/simple/helpers/DummyUser.php
index 8d38582..8b00bd1 100644
--- a/tests/cases/simple/helpers/DummyUser.php
+++ b/tests/cases/simple/helpers/DummyUser.php
@@ -1,5 +1,6 @@
 <?php
 
+declare(strict_types=1);
 
 namespace app\simple\helpers;
 
diff --git a/tests/cases/simple/helpers/EmptyString.php b/tests/cases/simple/helpers/EmptyString.php
index bcd3f74..feeb241 100644
--- a/tests/cases/simple/helpers/EmptyString.php
+++ b/tests/cases/simple/helpers/EmptyString.php
@@ -1,5 +1,6 @@
 <?php
 
+declare(strict_types=1);
 
 namespace app\simple\helpers;
 
diff --git a/tests/cases/sqlite/fixtures/TestFixture.php b/tests/cases/sqlite/fixtures/TestFixture.php
index f57b62f..04c66a9 100644
--- a/tests/cases/sqlite/fixtures/TestFixture.php
+++ b/tests/cases/sqlite/fixtures/TestFixture.php
@@ -1,4 +1,7 @@
 <?php
+
+declare(strict_types=1);
+
 namespace tests\fixtures;
 
 
diff --git a/tests/cases/sqlite/functional/SqLiteCest.php b/tests/cases/sqlite/functional/SqLiteCest.php
index a581be8..1670ee0 100644
--- a/tests/cases/sqlite/functional/SqLiteCest.php
+++ b/tests/cases/sqlite/functional/SqLiteCest.php
@@ -1,4 +1,7 @@
 <?php
+
+declare(strict_types=1);
+
 namespace tests;
 
 use tests\fixtures\TestFixture;
@@ -23,16 +26,16 @@ public function testSharedPDO(FunctionalTester $I)
     {
         /** @var Connection $db1 */
         $db1 = $I->grabComponent('db1');
-        $I->assertEquals(['test'], $db1->schema->getTableNames('', true));
+        $I->assertSame(['test'], $db1->schema->getTableNames('', true));
 
         /** @var Connection $db21 */
         $db21 = $I->grabComponent('db21');
-        $I->assertEquals(['test'], $db21->schema->getTableNames('', true));
+        $I->assertSame(['test'], $db21->schema->getTableNames('', true));
 
         /** @var Connection $db22 */
         $db22 = $I->grabComponent('db22');
 
-        $I->assertEquals(['test'], $db22->schema->getTableNames('', true));
+        $I->assertSame(['test'], $db22->schema->getTableNames('', true));
     }
 
     public function testTransaction(FunctionalTester $I)