diff --git a/src/User/Helper/SecurityHelper.php b/src/User/Helper/SecurityHelper.php
index dd130dd..5fec4ab 100644
--- a/src/User/Helper/SecurityHelper.php
+++ b/src/User/Helper/SecurityHelper.php
@@ -11,6 +11,7 @@
 
 namespace Da\User\Helper;
 
+use Yii;
 use yii\base\Exception;
 use yii\base\Security;
 use yii\base\InvalidConfigException;
@@ -61,17 +62,29 @@ class SecurityHelper
         return $this->security->validatePassword($password, $hash);
     }
 
-    public function generatePassword($length, $minPasswordRequirements)
+    public function generatePassword($length, $minPasswordRequirements = null)
     {
         $sets = [
             'lower' => 'abcdefghjkmnpqrstuvwxyz',
             'upper' => 'ABCDEFGHJKMNPQRSTUVWXYZ',
             'digit' => '123456789',
-            'special' => '!#$%&()*+,-./:;<=>?@[\]^_{|}~'
+            'special' => '!#$%&*+,-.:;<=>?@_~'
         ];
         $all = '';
         $password = '';
 
+        if (!isset($minPasswordRequirements)) {
+            if (isset(Yii::$app->getModule('user')->minPasswordRequirements)) {
+                $minPasswordRequirements = Yii::$app->getModule('user')->minPasswordRequirements;
+            }
+            else {
+                $minPasswordRequirements = [
+                    'lower' => 1,
+                    'digit' => 1,
+                    'upper' => 1,
+                ];
+            }
+        }
         if (isset($minPasswordRequirements['min']) && $length < $minPasswordRequirements['min']) {
             $length = $minPasswordRequirements['min'];
         }
diff --git a/tests/unit/GeneratePasswordTest.php b/tests/unit/GeneratePasswordTest.php
new file mode 100644
index 0000000..2e4168f
--- /dev/null
+++ b/tests/unit/GeneratePasswordTest.php
@@ -0,0 +1,160 @@
+<?php
+
+use Da\User\Helper\SecurityHelper;
+use yii\base\Security;
+
+/**
+ * Testing for the `SecurityHelper.generatePassword()` function.
+ * Note that this test considers these sets of characters:
+ * $sets = [
+ *      'lower' => 'abcdefghjkmnpqrstuvwxyz',
+ *      'upper' => 'ABCDEFGHJKMNPQRSTUVWXYZ',
+ *      'digit' => '123456789',
+ *      'special' => '!#$%&*+,-.:;<=>?@_~'
+ * ];
+ */
+class GeneratePasswordTest extends \Codeception\Test\Unit
+{
+    const ITERATIONS = 10000;
+
+    // Test with minPasswordRequirements equal to null (get default value/parameter)
+    public function testNullParameter ()
+    {
+        $length = 8;
+        $minPasswordRequirements = null;
+        // Helper
+        $securityHelper = new SecurityHelper(new Security()); // Empty security (it does not matter)
+        // Check password correctness
+        $ok = true;
+        for ($i = 0; $i < self::ITERATIONS; $i++) {
+            $password = $securityHelper->generatePassword($length, $minPasswordRequirements);
+            $result = preg_match('/\A(?=(.*\d){1})(?=(?:[^a-z]*[a-z]){1})(?=(?:[^A-Z]*[A-Z]){1})[0-9a-zA-Z!#$%&*+,-.:;<=>?@_~]{8,}\z/', $password);
+            if ($result === 0) {
+                $ok = false;
+                break;
+            }
+        }
+        $this->assertTrue($ok);
+    }
+
+    // Test with minPasswordRequirements equal to an empty array (= password without requirements)
+    public function testEmptyParameter ()
+    {
+        $length = 8;
+        $minPasswordRequirements = [];
+        // Helper
+        $securityHelper = new SecurityHelper(new Security()); // Empty security (it does not matter)
+        // Check password correctness
+        $ok = true;
+        for ($i = 0; $i < self::ITERATIONS; $i++) {
+            $password = $securityHelper->generatePassword($length, $minPasswordRequirements);
+            $result = preg_match('/\A[0-9a-zA-Z!#$%&*+,-.:;<=>?@_~]{8,}\z/', $password);
+            if ($result === 0) {
+                $ok = false;
+                break;
+            }
+        }
+        $this->assertTrue($ok);
+    }
+
+    // Test with many lowercase characters, one uppercase character, one digit and one special character
+    public function testManyLowercaseCharacter ()
+    {
+        // Function parameters
+        $length = 8;
+        $minPasswordRequirements = [
+            'min' => 10,
+            'special' => 1,
+            'digit' => 1,
+            'upper' => 1,
+            'lower' => 5
+        ];
+        // Helper
+        $securityHelper = new SecurityHelper(new Security()); // Empty security (it does not matter)
+        // Check password correctness
+        $ok = true;
+        for ($i = 0; $i < self::ITERATIONS; $i++) {
+            $password = $securityHelper->generatePassword($length, $minPasswordRequirements);
+            $result = preg_match('/\A(?=(.*\d){1})(?=(?:[^a-z]*[a-z]){5})(?=(?:[^A-Z]*[A-Z]){1})(?=(?:[0-9a-zA-Z]*[!#$%&*+,-.:;<=>?@_~]){1})[0-9a-zA-Z!#$%&*+,-.:;<=>?@_~]{10,}\z/', $password);
+            if ($result === 0) {
+                $ok = false;
+                break;
+            }
+        }
+        $this->assertTrue($ok);
+    }
+
+    // Test with many special characters, one uppercase character, one digit
+    public function testManySpecialCharacter ()
+    {
+        // Function parameters
+        $length = 10;
+        $minPasswordRequirements = [
+            'min' => 10,
+            'special' => 6,
+            'digit' => 1,
+            'upper' => 1,
+        ];
+        // Helper
+        $securityHelper = new SecurityHelper(new Security()); // Empty security (it does not matter)
+        // Check password correctness
+        $ok = true;
+        for ($i = 0; $i < self::ITERATIONS; $i++) {
+            $password = $securityHelper->generatePassword($length, $minPasswordRequirements);
+            $result = preg_match('/\A(?=(.*\d){1})(?=(?:[^A-Z]*[A-Z]){1})(?=(?:[0-9a-zA-Z]*[!#$%&*+,-.:;<=>?@_~]){6})[0-9a-zA-Z!#$%&*+,-.:;<=>?@_~]{10,}\z/', $password);
+            if ($result === 0) {
+                $ok = false;
+                break;
+            }
+        }
+        $this->assertTrue($ok);
+    }
+
+    // Test with a long password and no requirements
+    public function testLongPassword ()
+    {
+        // Function parameters
+        $length = 20;
+        $minPasswordRequirements = [];
+        // Helper
+        $securityHelper = new SecurityHelper(new Security()); // Empty security (it does not matter)
+        // Check password correctness
+        $ok = true;
+        for ($i = 0; $i < self::ITERATIONS; $i++) {
+            $password = $securityHelper->generatePassword($length, $minPasswordRequirements);
+            $result = preg_match('/\A[0-9a-zA-Z!#$%&*+,-.:;<=>?@_~]{20,}\z/', $password);
+            if ($result === 0) {
+                $ok = false;
+                break;
+            }
+        }
+        $this->assertTrue($ok);
+    }
+
+    // Test with random requirements
+    public function testRandomRequirements ()
+    {
+        // Function parameters
+        $length = 8;
+        $minPasswordRequirements = [
+            'min' => 10,
+            'special' => 4,
+            'digit' => 3,
+            'upper' => 2,
+            'lower' => 1
+        ];
+        // Helper
+        $securityHelper = new SecurityHelper(new Security()); // Empty security (it does not matter)
+        // Check password correctness
+        $ok = true;
+        for ($i = 0; $i < self::ITERATIONS; $i++) {
+            $password = $securityHelper->generatePassword($length, $minPasswordRequirements);
+            $result = preg_match('/\A(?=(.*\d){3})(?=(?:[^a-z]*[a-z]){1})(?=(?:[^A-Z]*[A-Z]){2})(?=(?:[0-9a-zA-Z]*[!#$%&*+,-.:;<=>?@_~]){4})[0-9a-zA-Z!#$%&*+,-.:;<=>?@_~]{10,}\z/', $password);
+            if ($result === 0) {
+                $ok = false;
+                break;
+            }
+        }
+        $this->assertTrue($ok);
+    }
+}
\ No newline at end of file