diff --git a/tests/test_trusted_metadata_set.py b/tests/test_trusted_metadata_set.py
index aa2d39e4..64b2bd77 100644
--- a/tests/test_trusted_metadata_set.py
+++ b/tests/test_trusted_metadata_set.py
@@ -131,6 +131,13 @@ def test_update(self):
         # the 4 top level metadata objects + 2 additional delegated targets
         self.assertTrue(len(self.trusted_set), 6)
 
+        count = 0
+        for md in self.trusted_set:
+            self.assertIsInstance(md, Metadata)
+            count += 1
+
+        self.assertTrue(count, 6)
+
     def test_out_of_order_ops(self):
         # Update timestamp before root is finished
         with self.assertRaises(RuntimeError):
@@ -214,6 +221,13 @@ def test_update_with_invalid_json(self):
 
             update_func(metadata)
 
+    def test_update_root_new_root(self):
+        # test that root can be updated with a new valid version
+        def root_new_version_modifier(root: Root) -> None:
+            root.version += 1
+
+        root = self.modify_metadata("root", root_new_version_modifier)
+        self.trusted_set.update_root(root)
 
     def test_update_root_new_root_cannot_be_verified_with_threshold(self):
         # new_root data with threshold which cannot be verified.
@@ -227,7 +241,6 @@ def test_update_root_new_root_ver_same_as_trusted_root_ver(self):
         with self.assertRaises(exceptions.ReplayedMetadataError):
             self.trusted_set.update_root(self.metadata["root"])
 
-
     def test_root_update_finished_expired(self):
         def root_expired_modifier(root: Root) -> None:
             root.expires = datetime(1970, 1, 1)
@@ -249,13 +262,15 @@ def version_modifier(timestamp: Timestamp) -> None:
         with self.assertRaises(exceptions.ReplayedMetadataError):
             self.trusted_set.update_timestamp(self.metadata["timestamp"])
 
-    def test_update_timestamp_snapshot_ver_below_trusted_snapshot_ver(self):
-        def version_modifier(timestamp: Timestamp) -> None:
-            timestamp.version = 3
+    def test_update_timestamp_snapshot_ver_below_current(self):
+        def bump_snapshot_version(timestamp: Timestamp) -> None:
+            timestamp.meta["snapshot.json"].version = 2
 
-        modified_timestamp = self.modify_metadata("timestamp", version_modifier)
-        self._root_updated_and_update_timestamp(modified_timestamp)
-        # new_timestamp.snapshot.version < trusted_timestamp.snapshot.version
+        # set current known snapshot.json version to 2
+        timestamp = self.modify_metadata("timestamp", bump_snapshot_version)
+        self._root_updated_and_update_timestamp(timestamp)
+
+        # newtimestamp.meta["snapshot.json"].version < trusted_timestamp.meta["snapshot.json"].version
         with self.assertRaises(exceptions.ReplayedMetadataError):
             self.trusted_set.update_timestamp(self.metadata["timestamp"])
 
@@ -269,6 +284,16 @@ def timestamp_expired_modifier(timestamp: Timestamp) -> None:
         with self.assertRaises(exceptions.ExpiredMetadataError):
             self.trusted_set.update_timestamp(timestamp)
 
+    def test_update_snapshot_length_or_hash_mismatch(self):
+        def modify_snapshot_length(timestamp: Timestamp) -> None:
+            timestamp.meta["snapshot.json"].length = 1
+
+        # set known snapshot.json length to 1
+        timestamp = self.modify_metadata("timestamp", modify_snapshot_length)
+        self._root_updated_and_update_timestamp(timestamp)
+
+        with self.assertRaises(exceptions.RepositoryError):
+            self.trusted_set.update_snapshot(self.metadata["snapshot"])
 
     def test_update_snapshot_cannot_verify_snapshot_with_threshold(self):
         self._root_updated_and_update_timestamp(self.metadata["timestamp"])
@@ -323,7 +348,6 @@ def snapshot_expired_modifier(snapshot: Snapshot) -> None:
         with self.assertRaises(exceptions.ExpiredMetadataError):
             self.trusted_set.update_snapshot(snapshot)
 
-
     def test_update_targets_no_meta_in_snapshot(self):
         def no_meta_modifier(snapshot: Snapshot) -> None:
             snapshot.meta = {}
diff --git a/tuf/ngclient/_internal/trusted_metadata_set.py b/tuf/ngclient/_internal/trusted_metadata_set.py
index 25c46cb1..369b5255 100644
--- a/tuf/ngclient/_internal/trusted_metadata_set.py
+++ b/tuf/ngclient/_internal/trusted_metadata_set.py
@@ -116,7 +116,7 @@ def __len__(self) -> int:
 
     def __iter__(self) -> Iterator[Metadata]:
         """Returns iterator over all Metadata objects in TrustedMetadataSet"""
-        return iter(self._trusted_set)
+        return iter(self._trusted_set.values())
 
     # Helper properties for top level metadata
     @property