diff --git a/src/magicbag/mock/int.py b/src/magicbag/mock/int.py
index e680c01..a17a61b 100644
--- a/src/magicbag/mock/int.py
+++ b/src/magicbag/mock/int.py
@@ -3,12 +3,24 @@
 import random
 
 
-def random_fixed_int(length):
+def random_fixed_int(length, negative=False):
     """Generate fix length random int.
 
     Args:
         fix_length (int): fix length
+        negetive (bool): if True, can generate negative int
     Return:
         (int): random int
     """
-    return random.randint(10 ** (length - 1), 10**length - 1)
+    # generate positive fixed length int
+    positive = random.randint(10 ** (length - 1), 10**length - 1)
+
+    # if negative is True, return positive or negative int
+    if negative:
+        if random.choice([True, False]):
+            return positive
+
+        return -positive
+
+    # not negative return positive
+    return positive