diff --git a/composer.json b/composer.json
index eba18fca..1c907091 100644
--- a/composer.json
+++ b/composer.json
@@ -1,7 +1,7 @@
 {
     "name": "mews/pos",
     "description": "Türk bankaları için sanal pos kütüphanesi",
-	"keywords": ["pos", "sanal pos", "est", "est pos", "akbank"],
+	"keywords": ["pos", "sanal pos", "est", "est pos", "akbank", "posnet", "payfor", "vakifbankpos"],
 	"homepage": "https://github.com/mewebstudio/pos",
     "license": "MIT",
     "authors": [
@@ -11,7 +11,7 @@
         }
     ],
     "require": {
-        "php": "^7.1.3",
+        "php": ">=7.1.3",
         "ext-dom": "*",
         "ext-json": "*",
         "ext-openssl": "*",
@@ -35,5 +35,8 @@
         "squizlabs/php_codesniffer": "^3.5",
         "escapestudios/symfony2-coding-standard": "^3.11",
         "symfony/var-dumper": "^5.1"
+    },
+    "config": {
+        "sort-packages": true
     }
 }
diff --git a/src/Entity/Card/AbstractCreditCard.php b/src/Entity/Card/AbstractCreditCard.php
index 6984570f..bc73a040 100644
--- a/src/Entity/Card/AbstractCreditCard.php
+++ b/src/Entity/Card/AbstractCreditCard.php
@@ -8,17 +8,18 @@
 abstract class AbstractCreditCard
 {
     /**
+     * 16 digit credit card number without spaces
      * @var string
      */
     protected $number;
 
     /**
-     * @var \DateTime
+     * @var \DateTimeImmutable
      */
     protected $expireYear;
 
     /**
-     * @var \DateTime
+     * @var \DateTimeImmutable
      */
     protected $expireMonth;
 
@@ -40,24 +41,31 @@ abstract class AbstractCreditCard
 
     /**
      * AbstractCreditCard constructor.
+     *
      * @param string      $number         credit card number with or without spaces
-     * @param string      $expireYear     accepts year in 1, 2 and 4 digit format. accepted year formats '1' (2001), '02' (2002), '20' (2020), '2024' (2024)
+     * @param string      $expireYear     accepts year in 1, 2 and 4 digit format. accepted year formats '1' (2001), '02'
+     *                                    (2002), '20' (2020), '2024' (2024)
      * @param string      $expireMonth    single digit or double digit month values are accepted
      * @param string      $cvv
      * @param string|null $cardHolderName
      * @param string|null $cardType       examples values: 'visa', 'master', '1', '2'
+     *
+     * @throws \DomainException
      */
     public function __construct(string $number, string $expireYear, string $expireMonth, string $cvv, ?string $cardHolderName = null, ?string $cardType = null)
     {
         $this->number = preg_replace('/\s+/', '', $number);
 
-        $yearFormat = 4 === strlen($expireYear) ? 'Y' : 'y';
-        $this->expireYear = \DateTime::createFromFormat($yearFormat, $expireYear);
+        $yearFormat        = 4 === strlen($expireYear) ? 'Y' : 'y';
+        $this->expireYear  = \DateTimeImmutable::createFromFormat($yearFormat, $expireYear);
+        $this->expireMonth = \DateTimeImmutable::createFromFormat('m', $expireMonth);
+        if (!$this->expireYear || !$this->expireMonth) {
+            throw new \DomainException('INVALID DATE FORMAT');
+        }
 
-        $this->expireMonth = \DateTime::createFromFormat('m', $expireMonth);
-        $this->cvv = $cvv;
+        $this->cvv        = $cvv;
         $this->holderName = $cardHolderName;
-        $this->type = $cardType;
+        $this->type       = $cardType;
     }
 
     /**
diff --git a/tests/Entity/Card/AbstractCreditCardTest.php b/tests/Entity/Card/AbstractCreditCardTest.php
new file mode 100644
index 00000000..102d58a2
--- /dev/null
+++ b/tests/Entity/Card/AbstractCreditCardTest.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace Mews\Pos\Tests\Entity\Card;
+
+use Mews\Pos\Entity\Card\AbstractCreditCard;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @covers \Mews\Pos\Entity\Card\AbstractCreditCard
+ */
+class AbstractCreditCardTest extends TestCase
+{
+    public function testInvalidDateException()
+    {
+        $testData = [
+            'number' => '1234567890123456',
+            'expireYear' => '',
+            'expireMonth' => '',
+            'cvv' => '123',
+        ];
+        $this->expectException(\DomainException::class);
+        $this->getMockForAbstractClass(AbstractCreditCard::class, $testData);
+    }
+}
diff --git a/tests/Gateways/VakifBankPostTest.php b/tests/Gateways/VakifBankPosTest.php
similarity index 99%
rename from tests/Gateways/VakifBankPostTest.php
rename to tests/Gateways/VakifBankPosTest.php
index 831afcc1..15fc9516 100644
--- a/tests/Gateways/VakifBankPostTest.php
+++ b/tests/Gateways/VakifBankPosTest.php
@@ -11,7 +11,7 @@
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Serializer\Encoder\XmlEncoder;
 
-class VakifBankPostTest extends TestCase
+class VakifBankPosTest extends TestCase
 {
     /**
      * @var VakifBankAccount