diff --git a/tests/test_udict.py b/tests/test_udict.py
index f473428..53251aa 100644
--- a/tests/test_udict.py
+++ b/tests/test_udict.py
@@ -5,11 +5,19 @@
 
 class UDictTestCase(unittest.TestCase):
     def test_init(self):
-        d = UDict(hello=1, hi=2, default=10)
-        d2 = UDict({'hello': 1, 'hi': 2})
+        d = UDict(hello=1, hi='world', default=10)
+        d2 = UDict({'hello': 1, 'hi': 'world'})
+        d3 = UDict()
         self.assertEqual(d.default, 10)
+        self.assertEqual(d2.default, None)
+        self.assertEqual(d3.default, None)
+
         self.assertDictEqual(d.dictionary, d2.dictionary)
+        self.assertDictEqual(d3.dictionary, {})
+
         self.assertEqual(d, d2)
+        self.assertNotEqual(d, d3)
+        self.assertNotEqual(d2, d3)
 
     def test_keys_values_items(self):
         d = UDict(hello=1, hi=2)
@@ -63,6 +71,9 @@ def test_get_item(self):
 
         self.assertEqual(d[1], d['hello'])
 
+        # not existent key
+        self.assertEqual(d['hey'], None)
+
     def test_set_item(self):
         d = UDict(hello=1, hi=2)
         d['hi'] = 3
@@ -96,6 +107,19 @@ def test_get(self):
         self.assertEqual(d.get(value=3, default='missing'), 'missing')
         self.assertEqual(d.get(value=3), None)
 
+        with self.assertRaises(ValueError):
+            d.get()
+        with self.assertRaises(ValueError):
+            d.get(index=2, value=1)
+        with self.assertRaises(ValueError):
+            d.get(index=2, key=2)
+        with self.assertRaises(ValueError):
+            d.get(value=1, key=4)
+        with self.assertRaises(ValueError):
+            d.get(value=1, key=4, index=3)
+        with self.assertRaises(IndexError):
+            d.get(index=4)
+
     def test_len_and_iter(self):
         d = UDict(hello=1, hi=2)
         self.assertEqual(len(d), 2)
diff --git a/ufpy/udict.py b/ufpy/udict.py
index bb61193..f5faa58 100644
--- a/ufpy/udict.py
+++ b/ufpy/udict.py
@@ -35,7 +35,7 @@ def __init__(self, *, default: CDV, **kwargs: VT): ...
     def __init__(self, dictionary: AnyDict[KT, VT] = None, *, default: CDV = None, **kwargs: VT):
         if isinstance(dictionary, UDict):
             dictionary = dictionary.dictionary
-        self.__dict = dictionary if dictionary else kwargs
+        self.__dict = dictionary or kwargs
         self.__default = default
     
     # dictionary
@@ -145,7 +145,9 @@ def __getitem__(self, key: KT | int | slice) -> UDict[KT, VT, DV] | VT:
 
     def __setitem__(self, key: KT | int | slice, value: VT | list[VT]) -> None:
         keys = self.__get_keys_from_slice_or_int(key)
-        values = [value] if not isinstance(value, (list, tuple)) else value
+
+        # Ensure 'values' is always a list for consistent processing
+        values = value if isinstance(value, (list, tuple)) else [value]
 
         if len(keys) > len(values):
             values.extend([values[-1] for _ in range(len(keys) - len(values) + 1)])
@@ -222,16 +224,16 @@ def get(
 
     # Len, iterator and reversed version
     def __len__(self) -> int:
-        return len(self.items)
+        return len(self.__dict)
     
     def __iter__(self) -> Iterator[tuple[KT, VT]]:
-        return iter(self.items)
+        return iter(self.__dict.items())
     
     # Booleans
     def is_empty(self) -> bool:
         return len(self) == 0
 
-    def __nonzero__(self) -> bool:
+    def __bool__(self) -> bool:
         return not self.is_empty()
 
     def __contains__(self, item: tuple[KT, VT] | list[KT | VT] | KT) -> bool: