diff --git a/gallery_dl/util.py b/gallery_dl/util.py
index 2ae6505d..cb99be68 100644
--- a/gallery_dl/util.py
+++ b/gallery_dl/util.py
@@ -87,6 +87,7 @@ def combine_dict(a, b):
             combine_dict(a[key], value)
         else:
             a[key] = value
+    return a
 
 
 def code_to_language(code, default=None):
diff --git a/test/test_util.py b/test/test_util.py
index 3283ff90..3c790992 100644
--- a/test/test_util.py
+++ b/test/test_util.py
@@ -9,6 +9,65 @@
 
 import unittest
 import gallery_dl.util as util
+import gallery_dl.exception as exception
+import sys
+
+
+class TestRange(unittest.TestCase):
+
+    def test_parse_range(self):
+        self.assertEqual(
+            util.parse_range(""),
+            [])
+        self.assertEqual(
+            util.parse_range("1-2"),
+            [(1, 2)])
+        self.assertEqual(
+            util.parse_range("-"),
+            [(1, sys.maxsize)])
+        self.assertEqual(
+            util.parse_range("-2,4,6-8,10-"),
+            [(1, 2), (4, 4), (6, 8), (10, sys.maxsize)])
+        self.assertEqual(
+            util.parse_range(" - 3 , 4-  4, 2-6"),
+            [(1, 3), (4, 4), (2, 6)])
+
+    def test_optimize_range(self):
+        self.assertEqual(
+            util.optimize_range([]),
+            [])
+        self.assertEqual(
+            util.optimize_range([(2, 4)]),
+            [(2, 4)])
+        self.assertEqual(
+            util.optimize_range([(2, 4), (6, 8), (10, 12)]),
+            [(2, 4), (6, 8), (10, 12)])
+        self.assertEqual(
+            util.optimize_range([(2, 4), (4, 6), (5, 8)]),
+            [(2, 8)])
+        self.assertEqual(
+            util.optimize_range([(1, 1), (2, 2), (3, 6), (8, 9)]),
+            [(1, 6), (8, 9)])
+
+    def test_range_predicate(self):
+        pred = util.RangePredicate(" - 3 , 4-  4, 2-6")
+        for i in range(6):
+            self.assertTrue(pred)
+        with self.assertRaises(exception.StopExtraction):
+            bool(pred)
+
+        pred = util.RangePredicate("1, 3, 5")
+        self.assertTrue(pred)
+        self.assertFalse(pred)
+        self.assertTrue(pred)
+        self.assertFalse(pred)
+        self.assertTrue(pred)
+        with self.assertRaises(exception.StopExtraction):
+            bool(pred)
+
+        pred = util.RangePredicate("")
+        with self.assertRaises(exception.StopExtraction):
+            bool(pred)
 
 
 class TestISO639_1(unittest.TestCase):
@@ -48,5 +107,32 @@ class TestISO639_1(unittest.TestCase):
             self.assertEqual(func(*args), result)
 
 
+class TestOther(unittest.TestCase):
+
+    def test_bdecode(self):
+        self.assertEqual(util.bdecode(""), 0)
+        self.assertEqual(util.bdecode("123"), 123)
+        self.assertEqual(util.bdecode("1111011", "01"), 123)
+        self.assertEqual(util.bdecode("AAAABAA", "BA"), 123)
+
+    def test_combine_dict(self):
+        self.assertEqual(
+            util.combine_dict({}, {}),
+            {})
+        self.assertEqual(
+            util.combine_dict({1: 1, 2: 2}, {2: 4, 4: 8}),
+            {1: 1, 2: 4, 4: 8})
+        self.assertEqual(
+            util.combine_dict(
+                {1: {11: 22, 12: 24}, 2: {13: 26, 14: 28}},
+                {1: {11: 33, 13: 39}, 2: "str"}),
+            {1: {11: 33, 12: 24, 13: 39}, 2: "str"})
+        self.assertEqual(
+            util.combine_dict(
+                {1: {2: {3: {4: {"1": "a", "2": "b"}}}}},
+                {1: {2: {3: {4: {"1": "A", "3": "C"}}}}}),
+            {1: {2: {3: {4: {"1": "A", "2": "b", "3": "C"}}}}})
+
+
 if __name__ == '__main__':
     unittest.main()