diff --git a/transcoder/video_test.py b/transcoder/video_test.py
new file mode 100644
index 0000000..33d8898
--- /dev/null
+++ b/transcoder/video_test.py
@@ -0,0 +1,72 @@
+"""Tests for the video module."""
+
+import unittest
+
+import screen
+import video
+
+
+class TestVideo(unittest.TestCase):
+    def test_diff_weights(self):
+        fs = video.FrameSequencer(mode=video.Mode.DHGR)
+        v = video.Video(fs, mode=video.Mode.DHGR)
+
+        frame = screen.MemoryMap(screen_page=1)
+        frame.page_offset[0, 0] = 0b1111111
+        frame.page_offset[0, 1] = 0b1010101
+
+        target_pixelmap = screen.DHGRBitmap(
+            main_memory=v.memory_map,
+            aux_memory=frame
+        )
+        self.assertEqual(
+            0b0000000101010100000001111111,
+            target_pixelmap.packed[0, 0])
+
+        diff = v._diff_weights(v.pixelmap, target_pixelmap, is_aux=True)
+
+        # Expect byte 0 to map to 0b00000000 01111111
+        expect0 = target_pixelmap.edit_distances[0][0b0000000001111111]
+
+        # Expect byte 2 to map to 0b000000000000 000101010100
+        expect2 = target_pixelmap.edit_distances[2][0b000101010100]
+
+        self.assertEqual(expect0, diff[0, 0])
+        self.assertEqual(expect2, diff[0, 1])
+
+        # Update aux frame
+        v.aux_memory_map.page_offset = frame.page_offset
+        v.pixelmap._pack()
+        self.assertEqual(
+            0b0000000101010100000001111111,
+            v.pixelmap.packed[0, 0]
+        )
+
+        # Encode new aux frame
+        frame = screen.MemoryMap(screen_page=1)
+        frame.page_offset[0, 0] = 0b1101101
+        frame.page_offset[0, 1] = 0b0110110
+
+        target_pixelmap = screen.DHGRBitmap(
+            main_memory=v.memory_map,
+            aux_memory=frame
+        )
+        self.assertEqual(
+            0b0000000011011000000001101101,
+            target_pixelmap.packed[0, 0]
+        )
+
+        diff = v._diff_weights(v.pixelmap, target_pixelmap, is_aux=True)
+
+        # Expect byte 0 to map to 0b01111111 01101101
+        expect0 = target_pixelmap.edit_distances[0][0b0111111101101101]
+
+        # Expect byte 2 to map to 0b000101010100 000011011000
+        expect2 = target_pixelmap.edit_distances[2][0b0000101010100000011011000]
+
+        self.assertEqual(expect0, diff[0, 0])
+        self.assertEqual(expect2, diff[0, 1])
+
+
+if __name__ == '__main__':
+    unittest.main()