style: auto-format with black + isort + prettier [skip ci-format-check]

Add comprehensive unit tests for VerificationCode domain entity:
- create() factory: basic, stripped recipient, custom code/ttl, uniqueness
- is_expired / is_used / is_valid properties
- mark_used() and increment_attempts()
- Direct construction, slots, equality

tests/unit/domain/test_verification_code.py

@@ -0,0 +1,280 @@
+"""VerificationCode 单元测试."""
+
+from __future__ import annotations
+
+from datetime import datetime, timedelta, timezone
+from unittest.mock import patch
+
+import pytest
+from domain.verification_code import VerificationCode
+
+
+class TestVerificationCodeCreate:
+    """create() 工厂方法测试."""
+
+    def test_create_basic(self):
+        vc = VerificationCode.create("test@example.com", "email_login")
+        assert vc.id is not None
+        assert len(vc.id) == 32
+        assert vc.recipient == "test@example.com"
+        assert vc.code_type == "email_login"
+        assert len(vc.code) == 6
+        assert vc.code.isdigit()
+        assert vc.used_at is None
+        assert vc.attempts == 0
+        assert vc.created_at is not None
+        assert vc.expires_at > vc.created_at
+
+    def test_create_recipient_stripped(self):
+        vc = VerificationCode.create("  test@example.com  ", "email_login")
+        assert vc.recipient == "test@example.com"
+
+    def test_create_custom_code(self):
+        vc = VerificationCode.create("test@example.com", "email_login", custom_code="123456")
+        assert vc.code == "123456"
+
+    def test_create_custom_ttl(self):
+        fixed_now = datetime(2026, 1, 1, 12, 0, 0, tzinfo=timezone.utc)
+        with patch("domain.verification_code.datetime") as mock_dt:
+            mock_dt.now.return_value = fixed_now
+            mock_dt.side_effect = lambda *a, **kw: datetime(*a, **kw)
+            vc = VerificationCode.create("test@example.com", "email_login", ttl_seconds=60)
+        assert vc.expires_at == fixed_now + timedelta(seconds=60)
+
+    def test_create_default_ttl_300(self):
+        fixed_now = datetime(2026, 1, 1, 12, 0, 0, tzinfo=timezone.utc)
+        with patch("domain.verification_code.datetime") as mock_dt:
+            mock_dt.now.return_value = fixed_now
+            mock_dt.side_effect = lambda *a, **kw: datetime(*a, **kw)
+            vc = VerificationCode.create("test@example.com", "email_login")
+        assert vc.expires_at == fixed_now + timedelta(seconds=300)
+
+    def test_create_unique_ids(self):
+        vc1 = VerificationCode.create("a@b.com", "email_login")
+        vc2 = VerificationCode.create("a@b.com", "email_login")
+        assert vc1.id != vc2.id
+
+    def test_create_unique_codes(self):
+        codes = set()
+        for _ in range(20):
+            vc = VerificationCode.create("a@b.com", "email_login")
+            codes.add(vc.code)
+        # 20个随机6位码几乎肯定不都一样
+        assert len(codes) > 1
+
+    def test_create_phone_recipient(self):
+        vc = VerificationCode.create("13800138000", "phone_login")
+        assert vc.recipient == "13800138000"
+        assert vc.code_type == "phone_login"
+
+    def test_create_all_code_types(self):
+        for ct in ["email_bind", "phone_bind", "email_login", "phone_login", "reset_password"]:
+            vc = VerificationCode.create("test@example.com", ct)
+            assert vc.code_type == ct
+
+
+class TestVerificationCodeIsExpired:
+    """is_expired 属性测试."""
+
+    def test_not_expired_future(self):
+        future = datetime.now(timezone.utc) + timedelta(hours=1)
+        vc = VerificationCode(
+            id="1",
+            recipient="a@b.com",
+            code="123456",
+            code_type="email_login",
+            expires_at=future,
+        )
+        assert vc.is_expired is False
+
+    def test_expired_past(self):
+        past = datetime.now(timezone.utc) - timedelta(hours=1)
+        vc = VerificationCode(
+            id="1",
+            recipient="a@b.com",
+            code="123456",
+            code_type="email_login",
+            expires_at=past,
+        )
+        assert vc.is_expired is True
+
+    def test_expired_boundary_exact(self):
+        # 用mock固定时间，expires_at等于当前时间不算过期
+        fixed_now = datetime(2026, 1, 1, 12, 0, 0, tzinfo=timezone.utc)
+        with patch("domain.verification_code.datetime") as mock_dt:
+            mock_dt.now.return_value = fixed_now
+            mock_dt.side_effect = lambda *a, **kw: datetime(*a, **kw)
+            vc = VerificationCode(
+                id="1",
+                recipient="a@b.com",
+                code="123456",
+                code_type="email_login",
+                expires_at=fixed_now,
+            )
+            assert vc.is_expired is False
+
+
+class TestVerificationCodeIsUsed:
+    """is_used 属性测试."""
+
+    def test_not_used_default(self):
+        vc = VerificationCode.create("a@b.com", "email_login")
+        assert vc.is_used is False
+
+    def test_is_used_after_mark(self):
+        vc = VerificationCode.create("a@b.com", "email_login")
+        vc.mark_used()
+        assert vc.is_used is True
+
+
+class TestVerificationCodeIsValid:
+    """is_valid 属性测试."""
+
+    def test_valid_fresh(self):
+        future = datetime.now(timezone.utc) + timedelta(hours=1)
+        vc = VerificationCode(
+            id="1",
+            recipient="a@b.com",
+            code="123456",
+            code_type="email_login",
+            expires_at=future,
+        )
+        assert vc.is_valid is True
+
+    def test_invalid_expired(self):
+        past = datetime.now(timezone.utc) - timedelta(hours=1)
+        vc = VerificationCode(
+            id="1",
+            recipient="a@b.com",
+            code="123456",
+            code_type="email_login",
+            expires_at=past,
+        )
+        assert vc.is_valid is False
+
+    def test_invalid_used(self):
+        future = datetime.now(timezone.utc) + timedelta(hours=1)
+        vc = VerificationCode(
+            id="1",
+            recipient="a@b.com",
+            code="123456",
+            code_type="email_login",
+            expires_at=future,
+        )
+        vc.mark_used()
+        assert vc.is_valid is False
+
+    def test_invalid_expired_and_used(self):
+        past = datetime.now(timezone.utc) - timedelta(hours=1)
+        vc = VerificationCode(
+            id="1",
+            recipient="a@b.com",
+            code="123456",
+            code_type="email_login",
+            expires_at=past,
+        )
+        vc.mark_used()
+        assert vc.is_valid is False
+
+
+class TestVerificationCodeMarkUsed:
+    """mark_used 方法测试."""
+
+    def test_mark_used_sets_timestamp(self):
+        vc = VerificationCode.create("a@b.com", "email_login")
+        assert vc.used_at is None
+        before = datetime.now(timezone.utc)
+        vc.mark_used()
+        after = datetime.now(timezone.utc)
+        assert vc.used_at is not None
+        assert before <= vc.used_at <= after
+
+    def test_mark_used_twice_overwrites(self):
+        vc = VerificationCode.create("a@b.com", "email_login")
+        vc.mark_used()
+        first = vc.used_at
+        # 时间足够短，一般不会不同，但确保可以重复调用
+        vc.mark_used()
+        assert vc.used_at is not None
+
+
+class TestVerificationCodeIncrementAttempts:
+    """increment_attempts 方法测试."""
+
+    def test_default_zero(self):
+        vc = VerificationCode.create("a@b.com", "email_login")
+        assert vc.attempts == 0
+
+    def test_increment_once(self):
+        vc = VerificationCode.create("a@b.com", "email_login")
+        vc.increment_attempts()
+        assert vc.attempts == 1
+
+    def test_increment_multiple(self):
+        vc = VerificationCode.create("a@b.com", "email_login")
+        for _i in range(5):
+            vc.increment_attempts()
+        assert vc.attempts == 5
+
+
+class TestVerificationCodeBasics:
+    """基础构造和 slots 测试."""
+
+    def test_direct_construction(self):
+        now = datetime.now(timezone.utc)
+        vc = VerificationCode(
+            id="abc123",
+            recipient="test@test.com",
+            code="000000",
+            code_type="email_bind",
+            expires_at=now + timedelta(minutes=5),
+            used_at=None,
+            attempts=0,
+            created_at=now,
+        )
+        assert vc.id == "abc123"
+        assert vc.recipient == "test@test.com"
+        assert vc.code == "000000"
+
+    def test_slots_no_extra_attrs(self):
+        vc = VerificationCode.create("a@b.com", "email_login")
+        with pytest.raises((AttributeError, TypeError)):
+            vc.new_field = "value"  # type: ignore[attr-defined]
+
+    def test_equality_same_id(self):
+        now = datetime(2026, 1, 1, 12, 0, 0, tzinfo=timezone.utc)
+        vc1 = VerificationCode(
+            id="same",
+            recipient="a@b.com",
+            code="111",
+            code_type="email_login",
+            expires_at=now,
+            created_at=now,
+        )
+        vc2 = VerificationCode(
+            id="same",
+            recipient="a@b.com",
+            code="111",
+            code_type="email_login",
+            expires_at=now,
+            created_at=now,
+        )
+        assert vc1 == vc2
+
+    def test_equality_different_id(self):
+        now = datetime.now(timezone.utc)
+        vc1 = VerificationCode(
+            id="id1",
+            recipient="a@b.com",
+            code="111",
+            code_type="email_login",
+            expires_at=now,
+        )
+        vc2 = VerificationCode(
+            id="id2",
+            recipient="a@b.com",
+            code="111",
+            code_type="email_login",
+            expires_at=now,
+        )
+        assert vc1 != vc2