diff --git a/src/Rule/MaxLength.php b/src/Rule/MaxLength.php
index 7f6f7c1..ad57558 100644
--- a/src/Rule/MaxLength.php
+++ b/src/Rule/MaxLength.php
@@ -2,6 +2,7 @@
 
 namespace Morebec\Validator\Rule;
 
+use InvalidArgumentException;
 use Morebec\Validator\ValidationRuleInterface;
 
 class MaxLength implements ValidationRuleInterface
@@ -16,8 +17,13 @@ class MaxLength implements ValidationRuleInterface
      */
     private $message;
 
-    public function __construct(int $length, ?string $message = null)
+    public function __construct(
+        int $length,
+        ?string $message = null
+    )
     {
+        if($length<0)
+            throw new InvalidArgumentException();
         $this->length = $length;
         $this->message = $message;
     }
@@ -35,6 +41,6 @@ public function validate($v): bool
      */
     public function getMessage($v): string
     {
-        return $this->message ?: "The length of '{$v}' was expected to be at most {$this->length} characters long";
+        return $this->message?:"The length of '{$v}' was expected to be at most {$this->length} characters long";
     }
 }
diff --git a/src/Rule/MinLength.php b/src/Rule/MinLength.php
new file mode 100644
index 0000000..8e951bf
--- /dev/null
+++ b/src/Rule/MinLength.php
@@ -0,0 +1,56 @@
+<?php
+
+namespace Morebec\Validator\Rule;
+
+
+use InvalidArgumentException;
+use Morebec\Validator\ValidationRuleInterface;
+
+class MinLength implements ValidationRuleInterface
+{
+    /**
+     * @var int
+     */
+    private $minLength;
+
+    /**
+     * @var string|null
+     */
+    private $message;
+
+    /**
+     * MinLength constructor.
+     * @param int $minLength
+     * @param string|null $message
+     */
+    public function __construct(
+        int $minLength,
+        ?string $message = null
+    )
+    {
+        if($minLength<0)
+            throw new InvalidArgumentException();
+        $this->minLength = $minLength;
+        $this->message = $message;
+    }
+
+    /**
+     * Validates a value according to this rule and returns if it is valid or not
+     * @param mixed $v
+     * @return bool true if valid, otherwise false
+     */
+    public function validate($v): bool
+    {
+        return strlen($v)>=$this->minLength;
+    }
+
+    /**
+     * Returns the message to be used in case the validation did not pass
+     * @param mixed $v the value that did not pass the validation
+     * @return string
+     */
+    public function getMessage($v): string
+    {
+        return $this->message?:"'${$v}' is supposed to be at least ".$this->minLength." characters long.";
+    }
+}
\ No newline at end of file
diff --git a/tests/Rule/MaxLengthTest.php b/tests/Rule/MaxLengthTest.php
index 1125fc1..b6c687c 100644
--- a/tests/Rule/MaxLengthTest.php
+++ b/tests/Rule/MaxLengthTest.php
@@ -3,6 +3,7 @@
 namespace Tests\Morebec\Validator\Rule;
 
 use Morebec\Validator\Rule\MaxLength;
+use InvalidArgumentException;
 use PHPUnit\Framework\TestCase;
 
 class MaxLengthTest extends TestCase
@@ -10,16 +11,18 @@ class MaxLengthTest extends TestCase
     public function testValidate()
     {
         $firstRule = new MaxLength(5);
-        $secondRule = new MaxLength(5, 'Custom message');
-        $this->assertTrue($firstRule->validate('test'));
-        $this->assertFalse($firstRule->validate('long test'));
+        $secondRule = new MaxLength(5,"Custom message");
+        $this->assertTrue($firstRule->validate("test"));
+        $this->assertFalse($firstRule->validate("long test"));
         $this->assertEquals(
             "The length of 'arr' was expected to be at most 5 characters long",
-            $firstRule->getMessage('arr')
+            $firstRule->getMessage("arr")
         );
         $this->assertEquals(
-            'Custom message',
-            $secondRule->getMessage('arr')
+            "Custom message",
+            $secondRule->getMessage("arr")
         );
+        $this->expectException(InvalidArgumentException::class);
+        $thirdRule = new MaxLength(-1);
     }
 }
diff --git a/tests/Rule/MinLengthTest.php b/tests/Rule/MinLengthTest.php
new file mode 100644
index 0000000..4d43982
--- /dev/null
+++ b/tests/Rule/MinLengthTest.php
@@ -0,0 +1,22 @@
+<?php
+
+namespace Tests\Morebec\Validator\Rule;
+
+
+use InvalidArgumentException;
+use Morebec\Validator\Rule\MinLength;
+use PHPUnit\Framework\TestCase;
+
+class MinLengthTest extends TestCase
+{
+    public function testValidate(){
+        $ruleFirst = new MinLength(4);
+        $ruleSecond = new MinLength(4,"Custom message");
+
+        $this->assertTrue($ruleFirst->validate("test string"));
+        $this->assertFalse($ruleFirst->validate("tes"));
+        $this->assertEquals("Custom message",$ruleSecond->getMessage("test"));
+        $this->expectException(InvalidArgumentException::class);
+        $ruleThird = new MinLength(-1);
+    }
+}
\ No newline at end of file