diff --git a/tests/test_construct.py b/tests/test_construct.py
new file mode 100644
index 0000000..ad409b1
--- /dev/null
+++ b/tests/test_construct.py
@@ -0,0 +1,26 @@
+#!/usr/bin/env python3
+
+import unittest
+from pySim.construct import GreedyInteger
+
+tests = [
+        ( b'\x80', 0x80 ),
+        ( b'\x80\x01', 0x8001 ),
+        ( b'\x80\x00\x01', 0x800001 ),
+        ( b'\x80\x23\x42\x01', 0x80234201 ),
+        ]
+
+class TestGreedyInt(unittest.TestCase):
+    def test_GreedyInt_decoder(self):
+        gi = GreedyInteger()
+        for t in tests:
+            self.assertEqual(gi.parse(t[0]), t[1])
+    def test_GreedyInt_encoder(self):
+        gi = GreedyInteger()
+        for t in tests:
+            self.assertEqual(t[0], gi.build(t[1]))
+        pass
+
+
+if __name__ == "__main__":
+	unittest.main()