diff --git a/tests/test_utils/testdata_reader.py b/tests/test_utils/testdata_reader.py
index 3a4baee..f310d41 100644
--- a/tests/test_utils/testdata_reader.py
+++ b/tests/test_utils/testdata_reader.py
@@ -1,9 +1,19 @@
+"""
+Helper functions to deal with zip-encrypted test files.
+
+Some test samples alerted antivirus software when installing oletools. Those
+samples were therefore "hidden" in encrypted zip-files. These functions help
+using them.
+"""
+
 import os, sys, zipfile
 from os.path import dirname, abspath, normpath, join
 from . import DATA_BASE_DIR
 
+# Passwort used to encrypt problematic test samples inside a zip container
 ENCRYPTED_FILES_PASSWORD='infected-test'
 
+# import zipfile in a way compatible with all kinds of old python versions
 if sys.version_info[0] <= 2:
     # Python 2.x
     if sys.version_info[1] <= 6:
@@ -18,11 +28,23 @@ else:
     from zipfile import is_zipfile
     ENCRYPTED_FILES_PASSWORD = ENCRYPTED_FILES_PASSWORD.encode()
 
+
 def read(relative_path):
+    """
+    Return contents of unencrypted file inside test data dir.
+
+    see also: `read_encrypted`.
+    """
     with open(get_path_from_root(relative_path), 'rb') as file_handle:
         return file_handle.read()
 
+
 def read_encrypted(relative_path, filename=None):
+    """
+    Return contents of encrypted file inside test data dir.
+
+    see also: `read`.
+    """
     z = zipfile.ZipFile(get_path_from_root(relative_path))
 
     if filename == None:
@@ -33,5 +55,7 @@ def read_encrypted(relative_path, filename=None):
     z.close()
     return contents
 
+
 def get_path_from_root(relative_path):
-    return join(DATA_BASE_DIR, relative_path)
\ No newline at end of file
+    """Convert path relative to test data base dir to an absolute path."""
+    return join(DATA_BASE_DIR, relative_path)