1. Formatted the code with black.

2. Added tests for length parsing

Author: Ron Frenkel

emv/protocol/structures.py

@@ -1,5 +1,12 @@
 from collections import OrderedDict
-from .data import ELEMENT_FORMAT, render_element, read_tag, read_length, is_constructed, Tag
+from .data import (
+    ELEMENT_FORMAT,
+    render_element,
+    read_tag,
+    read_length,
+    is_constructed,
+    Tag,
+)
 from .data_elements import Parse, EPC_PRODUCT_ID
 from ..util import decode_int, bit_set
 import logging

emv/protocol/test/test_structures.py

@@ -31,6 +31,23 @@ def test_tlv(self):
         tlv = TLV.unmarshal(data)
         self.assertEqual(tlv[(0x9F, 0x17)][0], 3)
 
+    def test_length_parsing(self):
+        data = unformat_bytes("42 01 03")
+        tlv = TLV.unmarshal(data)
+        self.assertEqual(tlv[0x42][0], 3)
+
+        data = unformat_bytes("42 81 01 07")
+        tlv = TLV.unmarshal(data)
+        self.assertEqual(tlv[0x42][0], 7)
+
+        data = unformat_bytes("42 82 00 01 07")
+        tlv = TLV.unmarshal(data)
+        self.assertEqual(tlv[0x42][0], 7)
+
+        data = unformat_bytes("42 83 00 00 01 07")
+        tlv = TLV.unmarshal(data)
+        self.assertEqual(tlv[0x42][0], 7)
+
     def test_duplicate_tags(self):
         # An ADF entry with a number of records:
         data = unformat_bytes(