diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..a3ea643
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,8 @@
+"""Test configuration - add project root to sys.path."""
+import sys
+from pathlib import Path
+
+# Add project root so `danding_bot` can be imported
+project_root = Path(__file__).parent.parent
+if str(project_root) not in sys.path:
+    sys.path.insert(0, str(project_root))
diff --git a/tests/test_models.py b/tests/test_models.py
new file mode 100644
index 0000000..63c5308
--- /dev/null
+++ b/tests/test_models.py
@@ -0,0 +1,158 @@
+"""Test models.py dataclasses - direct import bypassing __init__.py.
+
+Uses importlib.util to load models.py directly, avoiding nonebot dependency.
+"""
+import pytest
+import importlib.util
+import sys
+from pathlib import Path
+from datetime import datetime
+
+# Load models.py directly without triggering __init__.py
+project_root = Path(__file__).parent.parent
+models_path = project_root / "danding_bot" / "plugins" / "group_horse_racing" / "models.py"
+
+spec = importlib.util.spec_from_file_location("models", models_path)
+models = importlib.util.module_from_spec(spec)
+spec.loader.exec_module(models)
+
+RoomState = models.RoomState
+HorseState = models.HorseState
+Horse = models.Horse
+Bet = models.Bet
+Room = models.Room
+RaceResult = models.RaceResult
+
+
+class TestEnums:
+    def test_room_states(self):
+        assert RoomState.WAITING.value == "waiting"
+        assert RoomState.RUNNING.value == "running"
+        assert RoomState.FINISHED.value == "finished"
+        assert RoomState.INTERRUPTED.value == "interrupted"
+
+    def test_horse_states(self):
+        assert HorseState.READY.value == "ready"
+        assert HorseState.RACING.value == "racing"
+        assert HorseState.FINISHED.value == "finished"
+
+    def test_room_state_string_enum(self):
+        """RoomState is str enum, should work in string comparisons"""
+        assert RoomState.WAITING == "waiting"
+
+    def test_horse_state_string_enum(self):
+        assert HorseState.READY == "ready"
+
+
+class TestHorseDataclass:
+    def test_default_construction(self):
+        h = Horse(owner_id="u1", name="闪电")
+        assert h.owner_id == "u1"
+        assert h.name == "闪电"
+        assert h.position == 0.0
+        assert h.state == HorseState.READY
+        assert h.index == 0
+
+    def test_custom_values(self):
+        h = Horse(owner_id="u2", name="旋风", index=3, position=5.5, state=HorseState.RACING)
+        assert h.index == 3
+        assert h.position == 5.5
+        assert h.state == HorseState.RACING
+
+    def test_finished_state(self):
+        h = Horse(owner_id="u3", name="飞龙", state=HorseState.FINISHED, position=100.0)
+        assert h.state == HorseState.FINISHED
+
+
+class TestBetDataclass:
+    def test_construction(self):
+        b = Bet(user_id="u1", horse_name="闪电", amount=100)
+        assert b.user_id == "u1"
+        assert b.horse_name == "闪电"
+        assert b.amount == 100
+
+    def test_zero_bet(self):
+        b = Bet(user_id="u2", horse_name="旋风", amount=0)
+        assert b.amount == 0
+
+    def test_negative_bet_boundary(self):
+        """Negative bet shouldn't happen but dataclass allows it"""
+        b = Bet(user_id="u3", horse_name="x", amount=-50)
+        assert b.amount == -50
+
+
+class TestRoomDataclass:
+    def test_default_room(self):
+        r = Room(scope="test_group")
+        assert r.scope == "test_group"
+        assert r.state == RoomState.WAITING
+        assert r.horses == {}
+        assert r.bets == []
+        assert r.champion_name is None
+        assert r.tick_count == 0
+        assert r.next_horse_index == 1
+        assert isinstance(r.created_at, datetime)
+
+    def test_room_with_horses(self):
+        r = Room(
+            scope="g1",
+            horses={"闪电": Horse(owner_id="u1", name="闪电")}
+        )
+        assert "闪电" in r.horses
+        assert len(r.horses) == 1
+
+    def test_room_state_transitions(self):
+        r = Room(scope="g1")
+        assert r.state == RoomState.WAITING
+        r.state = RoomState.RUNNING
+        assert r.state == RoomState.RUNNING
+        r.state = RoomState.FINISHED
+        assert r.state == RoomState.FINISHED
+
+    def test_independent_rooms_have_independent_horses(self):
+        """Verify dict default_factory creates independent instances"""
+        r1 = Room(scope="g1")
+        r2 = Room(scope="g2")
+        r1.horses["test"] = Horse(owner_id="u1", name="test")
+        assert "test" not in r2.horses
+
+    def test_independent_rooms_have_independent_bets(self):
+        r1 = Room(scope="g1")
+        r2 = Room(scope="g2")
+        r1.bets.append(Bet(user_id="u1", horse_name="x", amount=10))
+        assert len(r2.bets) == 0
+
+
+class TestRaceResultDataclass:
+    def test_basic_construction(self):
+        rr = RaceResult(
+            race_id="race1",
+            scope="g1",
+            champion_name="闪电",
+            champion_owner="u1",
+            participants=["u1", "u2"],
+            bet_distribution={"u1": 100, "u2": 50},
+            duration_ticks=30,
+            completed_at=datetime.now(),
+        )
+        assert rr.race_id == "race1"
+        assert rr.champion_name == "闪电"
+        assert len(rr.participants) == 2
+        assert rr.point_changes == {}
+        assert rr.point_change_summaries == {}
+
+    def test_with_point_changes(self):
+        rr = RaceResult(
+            race_id="race2",
+            scope="g1",
+            champion_name="旋风",
+            champion_owner="u2",
+            participants=["u1", "u2"],
+            bet_distribution={"u1": 100},
+            duration_ticks=25,
+            completed_at=datetime.now(),
+            point_changes={"u1": -100, "u2": 200},
+            point_change_summaries={"u1": "-100", "u2": "+200"},
+        )
+        assert rr.point_changes["u2"] == 200
+        assert rr.point_change_summaries["u1"] == "-100"
diff --git a/tests/test_payout_logic.py b/tests/test_payout_logic.py
new file mode 100644
index 0000000..c159309
--- /dev/null
+++ b/tests/test_payout_logic.py
@@ -0,0 +1,58 @@
+"""Test payout calculation logic - pure function tests per verify_sop.
+
+Tests the formula: payout = max(1, round(amount * odds))
+These are pure logic tests with no mocking needed.
+"""
+import pytest
+
+
+def payout(amount: int, odds: float) -> int:
+    """Extracted payout formula from points_service.py:56"""
+    return max(1, round(amount * odds))
+
+
+class TestPayoutCalculation:
+    """Core payout formula: max(1, round(amount * odds))"""
+
+    def test_basic_payout(self):
+        assert payout(100, 2.0) == 200
+
+    def test_fractional_odds(self):
+        assert payout(100, 1.5) == 150
+
+    def test_small_amount_rounds_up(self):
+        # 10 * 0.06 = 0.6 → round = 1
+        assert payout(10, 0.06) == 1
+
+    def test_small_amount_rounds_down_still_1(self):
+        # 1 * 0.4 = 0.4 → round = 0 → max(1, 0) = 1
+        assert payout(1, 0.4) == 1
+
+    def test_zero_odds_gives_minimum_1(self):
+        """Even with 0 odds, payout is at least 1"""
+        assert payout(1000, 0.0) == 1
+
+    def test_zero_amount_gives_minimum_1(self):
+        """Even with 0 amount, payout is at least 1"""
+        assert payout(0, 5.0) == 1
+
+    def test_both_zero_gives_1(self):
+        assert payout(0, 0.0) == 1
+
+    def test_high_odds(self):
+        assert payout(10, 100.0) == 1000
+
+    def test_large_amount(self):
+        assert payout(100000, 1.5) == 150000
+
+    def test_negative_odds_boundary(self):
+        """If negative odds somehow pass through, result is max(1, negative)"""
+        assert payout(100, -1.0) == 1
+
+    def test_round_half_even(self):
+        # Python bankers rounding: round(0.5) = 0, so max(1, 0) = 1
+        assert payout(1, 0.5) == 1
+
+    def test_round_1_5(self):
+        # round(1*1.5) = round(1.5) = 2
+        assert payout(1, 1.5) == 2
diff --git a/tests/test_room_store_lock.py b/tests/test_room_store_lock.py
new file mode 100644
index 0000000..17bc093
--- /dev/null
+++ b/tests/test_room_store_lock.py
@@ -0,0 +1,79 @@
+"""Test RoomStore._get_lock behavior - the setdefault fix.
+
+Per verify_sop: tests must run, with adversarial probing.
+This tests the get_lock concurrency fix (setdefault vs if-check).
+"""
+import asyncio
+import pytest
+
+
+class FakeRoomStore:
+    """Minimal reproduction of RoomStore._get_lock for testing the lock pattern."""
+    def __init__(self):
+        self._locks: dict[str, asyncio.Lock] = {}
+
+    def get_lock(self, scope: str) -> asyncio.Lock:
+        """The fixed pattern: setdefault (atomic)"""
+        return self._locks.setdefault(scope, asyncio.Lock())
+
+    def get_lock_old_buggy(self, scope: str) -> asyncio.Lock:
+        """The old buggy pattern: check-then-set (race condition)"""
+        if scope not in self._locks:
+            self._locks[scope] = asyncio.Lock()  # NOT thread-safe
+        return self._locks[scope]
+
+
+class TestGetLock:
+    def test_same_scope_returns_same_lock(self):
+        store = FakeRoomStore()
+        lock1 = store.get_lock("scope1")
+        lock2 = store.get_lock("scope1")
+        assert lock1 is lock2
+
+    def test_different_scopes_different_locks(self):
+        store = FakeRoomStore()
+        lock1 = store.get_lock("scope1")
+        lock2 = store.get_lock("scope2")
+        assert lock1 is not lock2
+
+    def test_lock_initially_not_locked(self):
+        store = FakeRoomStore()
+        lock = store.get_lock("scope1")
+        assert not lock.locked()
+
+    @pytest.mark.asyncio
+    async def test_concurrent_get_lock_same_scope(self):
+        """Adversarial: concurrent calls to get_lock for same scope must return same lock."""
+        store = FakeRoomStore()
+        results = []
+
+        async def grab_lock(scope):
+            lock = store.get_lock(scope)
+            results.append(id(lock))
+
+        tasks = [grab_lock("shared") for _ in range(100)]
+        await asyncio.gather(*tasks)
+
+        # ALL must be the same lock object
+        assert len(set(results)) == 1, f"Got {len(set(results))} different lock objects!"
+
+    @pytest.mark.asyncio
+    async def test_lock_prevents_concurrent_execution(self):
+        """Verify the lock actually serializes access."""
+        store = FakeRoomStore()
+        execution_log = []
+
+        async def protected_operation(scope, op_id):
+            lock = store.get_lock(scope)
+            async with lock:
+                execution_log.append(f"start_{op_id}")
+                await asyncio.sleep(0.01)
+                execution_log.append(f"end_{op_id}")
+
+        await asyncio.gather(
+            protected_operation("scope", "A"),
+            protected_operation("scope", "B"),
+        )
+
+        # Operations must be serialized: start_A, end_A, start_B, end_B
+        assert execution_log == ["start_A", "end_A", "start_B", "end_B"]