diff --git a/changelog.d/3958.misc b/changelog.d/3958.misc
new file mode 100644
index 0000000000..5931d06dcf
--- /dev/null
+++ b/changelog.d/3958.misc
@@ -0,0 +1 @@
+Fix docstrings and add tests for state store methods
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index 4b971efdba..3f4cbd61c4 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -255,7 +255,17 @@ class StateGroupWorkerStore(EventsWorkerStore, SQLBaseStore):
         )
 
     @defer.inlineCallbacks
-    def get_state_groups_ids(self, room_id, event_ids):
+    def get_state_groups_ids(self, _room_id, event_ids):
+        """Get the event IDs of all the state for the state groups for the given events
+
+        Args:
+            _room_id (str): id of the room for these events
+            event_ids (iterable[str]): ids of the events
+
+        Returns:
+            Deferred[dict[int, dict[tuple[str, str], str]]]:
+                dict of state_group_id -> (dict of (type, state_key) -> event id)
+        """
         if not event_ids:
             defer.returnValue({})
 
@@ -270,7 +280,7 @@ class StateGroupWorkerStore(EventsWorkerStore, SQLBaseStore):
 
     @defer.inlineCallbacks
     def get_state_ids_for_group(self, state_group):
-        """Get the state IDs for the given state group
+        """Get the event IDs of all the state in the given state group
 
         Args:
             state_group (int)
@@ -286,7 +296,9 @@ class StateGroupWorkerStore(EventsWorkerStore, SQLBaseStore):
     def get_state_groups(self, room_id, event_ids):
         """ Get the state groups for the given list of event_ids
 
-        The return value is a dict mapping group names to lists of events.
+        Returns:
+            Deferred[dict[int, list[EventBase]]]:
+                dict of state_group_id -> list of state events.
         """
         if not event_ids:
             defer.returnValue({})
@@ -324,7 +336,9 @@ class StateGroupWorkerStore(EventsWorkerStore, SQLBaseStore):
                 member events (if True), or to exclude member events (if False)
 
         Returns:
-            dictionary state_group -> (dict of (type, state_key) -> event id)
+        Returns:
+            Deferred[dict[int, dict[tuple[str, str], str]]]:
+                dict of state_group_id -> (dict of (type, state_key) -> event id)
         """
         results = {}
 
@@ -732,8 +746,8 @@ class StateGroupWorkerStore(EventsWorkerStore, SQLBaseStore):
                 If None, `types` filtering is applied to all events.
 
         Returns:
-            Deferred[dict[int, dict[(type, state_key), EventBase]]]
-                a dictionary mapping from state group to state dictionary.
+            Deferred[dict[int, dict[tuple[str, str], str]]]:
+                dict of state_group_id -> (dict of (type, state_key) -> event id)
         """
         if types is not None:
             non_member_types = [t for t in types if t[0] != EventTypes.Member]
@@ -788,8 +802,8 @@ class StateGroupWorkerStore(EventsWorkerStore, SQLBaseStore):
                 If None, `types` filtering is applied to all events.
 
         Returns:
-            Deferred[dict[int, dict[(type, state_key), EventBase]]]
-                a dictionary mapping from state group to state dictionary.
+            Deferred[dict[int, dict[tuple[str, str], str]]]:
+                dict of state_group_id -> (dict of (type, state_key) -> event id)
         """
         if types:
             types = frozenset(types)
diff --git a/tests/storage/test_state.py b/tests/storage/test_state.py
index b910965932..b9c5b39d59 100644
--- a/tests/storage/test_state.py
+++ b/tests/storage/test_state.py
@@ -74,6 +74,45 @@ class StateStoreTestCase(tests.unittest.TestCase):
             self.assertEqual(s1[t].event_id, s2[t].event_id)
         self.assertEqual(len(s1), len(s2))
 
+    @defer.inlineCallbacks
+    def test_get_state_groups_ids(self):
+        e1 = yield self.inject_state_event(
+            self.room, self.u_alice, EventTypes.Create, '', {}
+        )
+        e2 = yield self.inject_state_event(
+            self.room, self.u_alice, EventTypes.Name, '', {"name": "test room"}
+        )
+
+        state_group_map = yield self.store.get_state_groups_ids(self.room, [e2.event_id])
+        self.assertEqual(len(state_group_map), 1)
+        state_map = list(state_group_map.values())[0]
+        self.assertDictEqual(
+            state_map,
+            {
+                (EventTypes.Create, ''): e1.event_id,
+                (EventTypes.Name, ''): e2.event_id,
+            },
+        )
+
+    @defer.inlineCallbacks
+    def test_get_state_groups(self):
+        e1 = yield self.inject_state_event(
+            self.room, self.u_alice, EventTypes.Create, '', {}
+        )
+        e2 = yield self.inject_state_event(
+            self.room, self.u_alice, EventTypes.Name, '', {"name": "test room"}
+        )
+
+        state_group_map = yield self.store.get_state_groups(
+            self.room, [e2.event_id])
+        self.assertEqual(len(state_group_map), 1)
+        state_list = list(state_group_map.values())[0]
+
+        self.assertEqual(
+            {ev.event_id for ev in state_list},
+            {e1.event_id, e2.event_id},
+        )
+
     @defer.inlineCallbacks
     def test_get_state_for_event(self):