diff --git a/rrr_test.py b/rrr_test.py
new file mode 100644
index 0000000000..decf7d3e2a
--- /dev/null
+++ b/rrr_test.py
@@ -0,0 +1,159 @@
+import json
+from time import monotonic, sleep
+
+import requests
+
+
+HOMESERVER = "http://localhost:8080"
+
+USER_1_TOK = "syt_dGVzdA_JUXtKQUUMnolcOezckNz_2eyt3H"
+USER_1_HEADERS = {"Authorization": f"Bearer {USER_1_TOK}"}
+
+USER_2_TOK = "syt_c2Vjb25k_ElKwbhaNqTgpfgFQcStD_2aiOcs"
+USER_2_HEADERS = {"Authorization": f"Bearer {USER_2_TOK}"}
+
+
+def _check_for_status(result):
+    # Similar to raise_for_status, but prints the error.
+    if 400 <= result.status_code:
+        error_msg = result.json()
+        result.raise_for_status()
+        print(error_msg)
+        exit(0)
+
+
+def _sync_and_show(room_id):
+    print("Syncing . . .")
+    result = requests.get(
+        f"{HOMESERVER}/_matrix/client/v3/sync",
+        headers=USER_1_HEADERS,
+        params={"filter": json.dumps({"room": {"timeline": {"limit": 30}}})},
+    )
+    _check_for_status(result)
+    sync_response = result.json()
+
+    room = sync_response["rooms"]["join"][room_id]
+
+    # Find read receipts (this assumes non-overlapping).
+    read_receipt_starts = {}  # start event -> users
+    read_receipt_ends = {}  # end event -> users
+    for event in room["ephemeral"]["events"]:
+        if event["type"] != "m.receipt":
+            continue
+
+        for event_id, content in event["content"].items():
+            for mxid, receipt in content["m.read"].items():
+                # Just care about the localpart of the MXID.
+                mxid = mxid.split(":", 1)[0]
+                read_receipt_starts.setdefault(
+                    receipt.get("start_event_id"), []
+                ).append(mxid)
+                read_receipt_ends.setdefault(event_id, []).append(mxid)
+
+    print(room["unread_notifications"])
+
+    if None in read_receipt_starts:
+        user_ids = ", ".join(sorted(read_receipt_starts[None]))
+        print(f"v--------- {user_ids} ---------v")
+
+    for event in room["timeline"]["events"]:
+        event_id = event["event_id"]
+
+        if event_id in read_receipt_starts:
+            user_ids = ", ".join(read_receipt_starts[event_id])
+            print(f"v--------- {user_ids} ---------v")
+
+        if event["type"] == "m.room.message":
+            msg = event["content"]["body"]
+            print(msg)
+
+        if event_id in read_receipt_ends:
+            user_ids = ", ".join(sorted(read_receipt_ends[event_id]))
+            print(f"^--------- {user_ids} ---------^")
+
+    print()
+    print()
+
+
+def main():
+    # Create a new room as user 2, add a bunch of messages.
+    result = requests.post(
+        f"{HOMESERVER}/_matrix/client/v3/createRoom",
+        json={"visibility": "public", "name": f"Road to Nowhere ({monotonic()})"},
+        headers=USER_2_HEADERS,
+    )
+    _check_for_status(result)
+    room_id = result.json()["room_id"]
+
+    # Second user joins the room.
+    result = requests.post(
+        f"{HOMESERVER}/_matrix/client/v3/rooms/{room_id}/join", headers=USER_1_HEADERS
+    )
+    _check_for_status(result)
+
+    # Sync user 1.
+    _sync_and_show(room_id)
+
+    # User 2 sends some messages.
+    event_ids = []
+    with open("road_to_no_where.txt", "r") as f:
+        count = 0
+        for line in f.readlines():
+            line = line.strip()
+            if not line:
+                continue
+
+            # Send a msg to the room.
+            result = requests.put(
+                f"{HOMESERVER}/_matrix/client/v3/rooms/{room_id}/send/m.room.message/msg{count}",
+                json={
+                    "msgtype": "m.text",
+                    "body": f"{count: >2}: {line}",
+                },
+                headers=USER_2_HEADERS,
+            )
+            _check_for_status(result)
+            event_ids.append(result.json()["event_id"])
+            sleep(1)
+
+            count += 1
+
+            if count == 17:  # End of second verse
+                break
+
+    # User 2 sends a read receipt.
+    print("@second reads to end")
+    result = requests.post(
+        f"{HOMESERVER}/_matrix/client/v3/rooms/{room_id}/receipt/m.read/{event_ids[-1]}",
+        headers=USER_2_HEADERS,
+        json={},
+    )
+    _check_for_status(result)
+
+    _sync_and_show(room_id)
+
+    # User 1 sends a read receipt.
+    print("@test reads from 3 -> 8")
+    result = requests.post(
+        f"{HOMESERVER}/_matrix/client/v3/rooms/{room_id}/receipt/m.read/{event_ids[8]}/{event_ids[3]}",
+        headers=USER_1_HEADERS,
+        json={},
+    )
+    _check_for_status(result)
+
+    _sync_and_show(room_id)
+
+    # User 1 sends another read receipt.
+    print("@test reads from 13 -> 14")
+    result = requests.post(
+        f"{HOMESERVER}/_matrix/client/v3/rooms/{room_id}/receipt/m.read/{event_ids[14]}/{event_ids[13]}",
+        headers=USER_1_HEADERS,
+        json={},
+    )
+    _check_for_status(result)
+
+    _sync_and_show(room_id)
+
+
+if __name__ == "__main__":
+    main()