diff --git a/tests/GUID/fromHexStringTest.php b/tests/GUID/fromHexStringTest.php
index dc67c98..5c31c29 100644
--- a/tests/GUID/fromHexStringTest.php
+++ b/tests/GUID/fromHexStringTest.php
@@ -12,6 +12,24 @@
  */
 class fromHexStringTestTest extends TestCase
 {
+    /**
+     * @expectedException \Unicity\Errors\GUIDInvariantsViolationError
+     * @expectedExceptionMessage IDs must have at least 6 bytes of entropy
+     */
+    public function test_too_small_expected_length()
+    {
+        GUID::fromHexString('abcd', 4);
+    }
+
+    /**
+     * @expectedException \Unicity\Errors\UnserializationError
+     * @expectedExceptionMessage The passed string has an unexpected length {"expected":6,"given":4}
+     */
+    public function test_unexpected_length()
+    {
+        GUID::fromHexString('abcdef01', 6);
+    }
+
     /**
      * @param string $invalidHexStr
      *
@@ -21,7 +39,7 @@ class fromHexStringTestTest extends TestCase
      */
     public function test_invalid_hex_strings(string $invalidHexStr)
     {
-        GUID::fromHexString($invalidHexStr, \strlen($invalidHexStr)/2);
+        GUID::fromHexString($invalidHexStr, (int)(\strlen($invalidHexStr)/2));
     }
 
     public function invalidHexStringsProvider()
@@ -29,7 +47,8 @@ public function invalidHexStringsProvider()
         return [
             ['xyxyxyxyxyxy'],
             ['abcdefABCDEF'],
-            ['0123456789a-']
+            ['0123456789a-'],
+            ['0123456789abc']
         ];
     }
 }