diff --git a/bulkredditdownloader/downloaders/base_downloader.py b/bulkredditdownloader/downloaders/base_downloader.py
index eb30431..7873db7 100644
--- a/bulkredditdownloader/downloaders/base_downloader.py
+++ b/bulkredditdownloader/downloaders/base_downloader.py
@@ -96,8 +96,9 @@ class BaseDownloader(ABC):
     @staticmethod
     def _get_extension(url: str) -> str:
         pattern = re.compile(r'(\.(jpg|jpeg|png|mp4|webm|gif))')
-        if len(results := re.search(pattern, url).groups()) > 1:
-            return results[1]
+        if results := re.search(pattern, url):
+            if len(results.groups()) > 1:
+                return results[0]
         if "v.redd.it" not in url:
             return '.jpg'
         else:
diff --git a/bulkredditdownloader/tests/__init__.py b/bulkredditdownloader/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/bulkredditdownloader/tests/downloaders/__init__.py b/bulkredditdownloader/tests/downloaders/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/bulkredditdownloader/tests/downloaders/test_base_downloader.py b/bulkredditdownloader/tests/downloaders/test_base_downloader.py
new file mode 100644
index 0000000..a87d426
--- /dev/null
+++ b/bulkredditdownloader/tests/downloaders/test_base_downloader.py
@@ -0,0 +1,42 @@
+#!/uasr/bin/env python3
+# coding=utf-8
+
+from pathlib import Path
+
+import pytest
+
+from bulkredditdownloader.downloaders.base_downloader import BaseDownloader
+
+
+@pytest.mark.parametrize(('test_bytes', 'expected'), ((b'test', '098f6bcd4621d373cade4e832627b4f6'),
+                                                      (b'test2', 'ad0234829205b9033196ba818f7a872b')))
+def test_create_hash(test_bytes: bytes, expected: str):
+    result = BaseDownloader._create_hash(test_bytes)
+    assert result == expected
+
+
+@pytest.mark.parametrize(('test_url', 'expected'), (('test.png', '.png'),
+                                                    ('random.jpg', '.jpg'),
+                                                    ('http://random.com/test.png', '.png'),
+                                                    ('https://example.net/picture.jpg', '.jpg'),
+                                                    ('https://v.redd.it/picture', '.mp4'),
+                                                    ('https://v.redd.it/picture.jpg', '.jpg'),
+                                                    ('https:/random.url', '.jpg')
+                                                    ))
+def test_get_extension(test_url: str, expected: str):
+    result = BaseDownloader._get_extension(test_url)
+    assert result == expected
+
+
+@pytest.mark.skip
+@pytest.mark.parametrize(('test_url', 'expected_hash'), (('https://www.iana.org/_img/2013.1/iana-logo-header.svg', ''),
+                                                         ('', '')
+                                                         ))
+def test_download_resource(test_url: str, expected_hash: str, tmp_path: Path):
+    test_file = tmp_path / 'test'
+    BaseDownloader._download_resource(test_file, tmp_path, test_url)
+    assert test_file.exists()
+    with open(test_file, 'rb') as file:
+        content = file.read()
+    hash_result = BaseDownloader._create_hash(content)
+    assert hash_result == expected_hash