diff --git a/clientapi/routing/state_test.go b/clientapi/routing/state_test.go
new file mode 100644
index 000000000..fef8017e3
--- /dev/null
+++ b/clientapi/routing/state_test.go
@@ -0,0 +1,199 @@
+package routing
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"testing"
+
+	rsapi "github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/dendrite/roomserver/types"
+	"github.com/matrix-org/dendrite/setup/config"
+	uapi "github.com/matrix-org/dendrite/userapi/api"
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/gomatrixserverlib/spec"
+	"github.com/matrix-org/util"
+	"gotest.tools/v3/assert"
+)
+
+var ()
+
+type testRoomserverAPI struct {
+	rsapi.RoomserverInternalAPI
+	t           *testing.T
+	roomState   map[gomatrixserverlib.StateKeyTuple]*types.HeaderedEvent
+	roomIDStr   string
+	roomVersion gomatrixserverlib.RoomVersion
+	userIDStr   string
+	// userID -> senderID
+	senderMapping map[string]string
+}
+
+func (s testRoomserverAPI) QueryLatestEventsAndState(
+	ctx context.Context,
+	req *rsapi.QueryLatestEventsAndStateRequest,
+	res *rsapi.QueryLatestEventsAndStateResponse,
+) error {
+	res.RoomExists = req.RoomID == s.roomIDStr
+	if !res.RoomExists {
+		return nil
+	}
+
+	res.StateEvents = []*types.HeaderedEvent{}
+	for _, stateKeyTuple := range req.StateToFetch {
+		val, ok := s.roomState[stateKeyTuple]
+		if ok && val != nil {
+			res.StateEvents = append(res.StateEvents, val)
+		}
+	}
+
+	return nil
+}
+
+func (s testRoomserverAPI) QueryMembershipForUser(
+	ctx context.Context,
+	req *rsapi.QueryMembershipForUserRequest,
+	res *rsapi.QueryMembershipForUserResponse,
+) error {
+	if req.UserID.String() == s.userIDStr {
+		res.HasBeenInRoom = true
+		res.IsInRoom = true
+		res.RoomExists = true
+		res.Membership = spec.Join
+	}
+
+	return nil
+}
+
+func (s testRoomserverAPI) QuerySenderIDForUser(
+	ctx context.Context,
+	roomID spec.RoomID,
+	userID spec.UserID,
+) (*spec.SenderID, error) {
+	sID, ok := s.senderMapping[userID.String()]
+	if ok {
+		sender := spec.SenderID(sID)
+		return &sender, nil
+	} else {
+		return nil, nil
+	}
+}
+
+func (s testRoomserverAPI) QueryUserIDForSender(
+	ctx context.Context,
+	roomID spec.RoomID,
+	senderID spec.SenderID,
+) (*spec.UserID, error) {
+	for uID, sID := range s.senderMapping {
+		if sID == string(senderID) {
+			parsedUserID, err := spec.NewUserID(uID, true)
+			if err != nil {
+				s.t.Fatalf("Mock QueryUserIDForSender failed: %s", err)
+			}
+			return parsedUserID, nil
+		}
+	}
+	return nil, nil
+}
+
+func (s testRoomserverAPI) QueryStateAfterEvents(
+	ctx context.Context,
+	req *rsapi.QueryStateAfterEventsRequest,
+	res *rsapi.QueryStateAfterEventsResponse,
+) error {
+	return nil
+}
+
+func Test_OnIncomingStateTypeRequest(t *testing.T) {
+	var tempRoomServerCfg config.RoomServer
+	tempRoomServerCfg.Defaults(config.DefaultOpts{})
+	defaultRoomVersion := tempRoomServerCfg.DefaultRoomVersion
+	pseudoIDRoomVersion := gomatrixserverlib.RoomVersionPseudoIDs
+
+	userIDStr := "@testuser:domain"
+	eventType := "com.example.test"
+	stateKey := "testStateKey"
+	roomIDStr := "!id:domain"
+
+	device := &uapi.Device{
+		UserID: userIDStr,
+	}
+
+	t.Run("request simple state key", func(t *testing.T) {
+		ctx := context.Background()
+
+		rsAPI := testRoomserverAPI{
+			roomVersion: defaultRoomVersion,
+			roomIDStr:   roomIDStr,
+			roomState: map[gomatrixserverlib.StateKeyTuple]*types.HeaderedEvent{
+				{
+					EventType: eventType,
+					StateKey:  stateKey,
+				}: mustCreateStatePDU(t, defaultRoomVersion, roomIDStr, eventType, stateKey, map[string]interface{}{
+					"foo": "bar",
+				}),
+			},
+			userIDStr: userIDStr,
+		}
+
+		jsonResp := OnIncomingStateTypeRequest(ctx, device, rsAPI, roomIDStr, eventType, stateKey, false)
+
+		assert.DeepEqual(t, jsonResp, util.JSONResponse{
+			Code: http.StatusOK,
+			JSON: spec.RawJSON(`{"foo":"bar"}`),
+		})
+	})
+
+	t.Run("user ID state keys are translated to pseudo IDs in pseudo ID rooms", func(t *testing.T) {
+		ctx := context.Background()
+
+		stateSenderUserID := "@sender:domain"
+		stateSenderRoomKey := "testsenderkey"
+
+		rsAPI := testRoomserverAPI{
+			roomVersion: pseudoIDRoomVersion,
+			roomIDStr:   roomIDStr,
+			roomState: map[gomatrixserverlib.StateKeyTuple]*types.HeaderedEvent{
+				{
+					EventType: eventType,
+					StateKey:  stateSenderRoomKey,
+				}: mustCreateStatePDU(t, pseudoIDRoomVersion, roomIDStr, eventType, stateSenderRoomKey, map[string]interface{}{
+					"foo": "bar",
+				}),
+			},
+			userIDStr: userIDStr,
+			senderMapping: map[string]string{
+				stateSenderUserID: stateSenderRoomKey,
+			},
+		}
+
+		jsonResp := OnIncomingStateTypeRequest(ctx, device, rsAPI, roomIDStr, eventType, stateSenderUserID, false)
+
+		assert.DeepEqual(t, jsonResp, util.JSONResponse{
+			Code: http.StatusOK,
+			JSON: spec.RawJSON(`{"foo":"bar"}`),
+		})
+	})
+}
+
+func mustCreateStatePDU(t *testing.T, roomVer gomatrixserverlib.RoomVersion, roomID string, stateType string, stateKey string, stateContent map[string]interface{}) *types.HeaderedEvent {
+	t.Helper()
+	roomVerImpl := gomatrixserverlib.MustGetRoomVersion(roomVer)
+
+	evBytes, err := json.Marshal(map[string]interface{}{
+		"room_id":   roomID,
+		"type":      stateType,
+		"state_key": stateKey,
+		"content":   stateContent,
+	})
+	if err != nil {
+		t.Fatalf("failed to create event: %v", err)
+	}
+
+	ev, err := roomVerImpl.NewEventFromTrustedJSON(evBytes, false)
+	if err != nil {
+		t.Fatalf("failed to create event: %v", err)
+	}
+
+	return &types.HeaderedEvent{PDU: ev}
+}