Add test_should_return_last_according_the_feed_order

podcast_downloader/downloaded.py

@@ -36,4 +36,11 @@ def get_downloaded_files(
 def get_last_downloaded_file_before_gap(
     feed_files: List[str], downloaded_files: Iterable[str]
 ) -> str:
-    return downloaded_files[-1] if downloaded_files else None
+    last_file = None
+    all_downloaded_files = set(downloaded_files)
+
+    for feed_file_name in feed_files:
+        if feed_file_name in all_downloaded_files:
+            last_file = feed_file_name
+
+    return last_file

tests/get_last_downloaded_file_before_gap_test.py

@@ -1,3 +1,4 @@
+from random import shuffle
 import unittest
 
 from podcast_downloader.downloaded import get_last_downloaded_file_before_gap
@@ -9,7 +10,7 @@ def test_should_return_none_for_empty_collections(self):
         result = get_last_downloaded_file_before_gap([], [])
 
         # Assert
-        self.assertIsNone(result)
+        self.assertIsNone(result, "On empty directory should be return None")
 
     def test_should_return_none_for_empty_directory_files(self):
         # Assign
@@ -24,7 +25,7 @@ def test_should_return_none_for_empty_directory_files(self):
         result = get_last_downloaded_file_before_gap(feed_files, [])
 
         # Assert
-        self.assertIsNone(result)
+        self.assertIsNone(result, "On empty directory should be return None")
 
     def test_should_return_last_for_nonempty_directory_files(self):
         # Assign
@@ -41,4 +42,27 @@ def test_should_return_last_for_nonempty_directory_files(self):
         result = get_last_downloaded_file_before_gap(feed_files, directory_files)
 
         # Assert
-        self.assertEqual(result, feed_files[-1])
+        self.assertEqual(
+            result, feed_files[-1], "Should return the last files from the feed"
+        )
+
+    def test_should_return_last_according_the_feed_order(self):
+        # Assign
+        feed_files = [
+            "podcast_episode_1.mp3",
+            "podcast_episode_2.mp3",
+            "podcast_episode_3.mp3",
+            "podcast_episode_4.mp3",
+        ]
+
+        directory_files = feed_files[0:-1]
+        shuffle(directory_files)
+        directory_files = directory_files[:1] + [feed_files[-1]] + directory_files[1:]
+
+        # Act
+        result = get_last_downloaded_file_before_gap(feed_files, directory_files)
+
+        # Assert
+        self.assertEqual(
+            result, feed_files[-1], "Should return the last files from the feed"
+        )