feat(billing): B-2.7 Stripe Checkout 3 plans CAD/TVQ + Apple/Google Pay

Adds the customer-facing checkout flow under /checkout/<plan>:
- src/billing/plans.py — Plan dataclass + 3 plans (DictIA 8 / 16 / Cloud),
  monthly + yearly Price IDs resolved from STRIPE_DICTIA_*_{SETUP,MONTHLY,YEARLY} env.
- src/billing/stripe_client.py — lazy stripe.api_key init, get_or_create_customer
  (persists user.stripe_customer_id), create_checkout_session with mode=subscription,
  currency=cad, automatic_tax=true (TPS 5% + TVQ 9.975%), billing_address_collection,
  metadata on both Session and Subscription for the B-2.8 webhook.
- src/billing/routes.py — GET /checkout/<plan>?period=monthly|yearly returns 303
  redirect to Stripe-hosted Checkout. Friendly French flash + redirect to /tarifs
  on unknown plan, missing STRIPE_SECRET_KEY, missing Price IDs, or Stripe API error.
  GET /checkout/success and /checkout/cancel render brand-tokenized templates that
  extend marketing/base.html.
- templates/billing/{success,cancel}.html — explicit "activé sous quelques minutes"
  note (webhook is async), aucun montant prélevé reassurance on cancel.
- config/env.stripe.example — env vars + Stripe Dashboard setup checklist
  (CAD activation, Stripe Tax registrations, Apple/Google Pay enable, webhook).
- tests/test_stripe_checkout.py — 25 tests covering plans, stripe_client, routes,
  and the _PUBLIC_INDEXABLE_ENDPOINTS integration. Stripe SDK mocked via
  unittest.mock.patch (no network). Windows manual driver included.

Webhook (B-2.8) will be the source of truth for user.subscription_status.
This task only mutates user.stripe_customer_id (identity, not state).
Existing pricing CTAs in templates/marketing/_partials/_pricing_tiers.html
already link to /checkout/<slug> (verified) — no marketing template touched.

Tests: 25/25 new + 89/89 prior pass on Windows manual driver.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/_run_stripe_checkout_windows.py

@@ -0,0 +1,74 @@
+"""Windows manual driver for tests/test_stripe_checkout.py.
+
+src/init_db.py imports `fcntl`, which is POSIX-only. On Windows we stub it
+before src.app gets imported, then run each test_* function and report.
+
+Run from the repo root:
+    py -3 tests/_run_stripe_checkout_windows.py
+"""
+import os
+import sys
+import types
+import traceback
+
+# 1) Stub fcntl BEFORE any import of src.* happens.
+if 'fcntl' not in sys.modules:
+    fcntl_stub = types.ModuleType('fcntl')
+    fcntl_stub.LOCK_EX = 2
+    fcntl_stub.LOCK_NB = 4
+    fcntl_stub.LOCK_UN = 8
+    fcntl_stub.LOCK_SH = 1
+    fcntl_stub.flock = lambda *_args, **_kw: None
+    fcntl_stub.fcntl = lambda *_args, **_kw: 0
+    sys.modules['fcntl'] = fcntl_stub
+
+# 2) Make repo root importable
+HERE = os.path.dirname(os.path.abspath(__file__))
+REPO = os.path.dirname(HERE)
+sys.path.insert(0, REPO)
+
+# 3) Test-friendly env defaults
+os.environ.setdefault('SQLALCHEMY_DATABASE_URI', 'sqlite:///:memory:')
+os.environ.setdefault('SECRET_KEY', 'test-secret-key-stripe')
+os.environ.setdefault('ENABLE_EMAIL_VERIFICATION', 'false')
+os.environ.setdefault('REQUIRE_EMAIL_VERIFICATION', 'false')
+os.environ.setdefault('TRANSCRIPTION_BASE_URL', 'http://test-stub')
+os.environ.setdefault('TRANSCRIPTION_API_KEY', 'test-stub')
+os.environ.setdefault('RATELIMIT_ENABLED', 'false')
+try:
+    sys.stdout.reconfigure(encoding='utf-8', errors='replace')
+    sys.stderr.reconfigure(encoding='utf-8', errors='replace')
+except Exception:
+    pass
+
+# 4) Import the test module and run every test_* function
+import importlib.util  # noqa: E402
+spec = importlib.util.spec_from_file_location(
+    'test_stripe_checkout',
+    os.path.join(HERE, 'test_stripe_checkout.py'),
+)
+mod = importlib.util.module_from_spec(spec)
+spec.loader.exec_module(mod)
+
+tests = [(name, fn) for name, fn in vars(mod).items()
+         if name.startswith('test_') and callable(fn)]
+
+passed = 0
+failed = []
+for name, fn in tests:
+    try:
+        fn()
+        print(f'  PASS  {name}')
+        passed += 1
+    except Exception as e:  # noqa: BLE001
+        print(f'  FAIL  {name}: {type(e).__name__}: {e}')
+        failed.append((name, traceback.format_exc()))
+
+total = len(tests)
+print()
+print(f'Result: {passed}/{total} passed, {len(failed)} failed')
+if failed:
+    print('\n--- Failures ---\n')
+    for name, tb in failed:
+        print(f'### {name}\n{tb}\n')
+sys.exit(0 if not failed else 1)

tests/test_stripe_checkout.py

@@ -0,0 +1,593 @@
+"""Tests for B-2.7 — Stripe Checkout (3 plans CAD + TPS/TVQ + Apple/Google Pay).
+
+Covers:
+  - plans.py: Plan dataclass, env-resolved Price IDs, helpers, is_configured.
+  - stripe_client.py: lazy api_key init, get_or_create_customer, create_checkout_session.
+  - routes.py: GET /checkout/<plan>, /checkout/success, /checkout/cancel.
+  - Integration: app.py _PUBLIC_INDEXABLE_ENDPOINTS includes 'billing.success'.
+
+Mocks the stripe library functions (stripe.Customer.create, stripe.checkout.Session.create)
+via unittest.mock.patch — no real Stripe API calls.
+
+Note: pytest cannot collect this file on Windows native because src/init_db.py
+imports `fcntl` (POSIX-only). Use tests/_run_stripe_checkout_windows.py.
+"""
+import os
+import sys
+from unittest.mock import patch, MagicMock
+
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+os.environ.setdefault('SQLALCHEMY_DATABASE_URI', 'sqlite:///:memory:')
+os.environ.setdefault('SECRET_KEY', 'test-secret-key-stripe')
+os.environ.setdefault('ENABLE_EMAIL_VERIFICATION', 'false')
+os.environ.setdefault('REQUIRE_EMAIL_VERIFICATION', 'false')
+os.environ.setdefault('RATELIMIT_ENABLED', 'false')
+
+from src.app import app, db, bcrypt  # noqa: E402
+from src.models.user import User  # noqa: E402
+
+
+_PRICE_ENV_VARS = (
+    'STRIPE_SECRET_KEY',
+    'STRIPE_DICTIA_8_SETUP', 'STRIPE_DICTIA_8_MONTHLY', 'STRIPE_DICTIA_8_YEARLY',
+    'STRIPE_DICTIA_16_SETUP', 'STRIPE_DICTIA_16_MONTHLY', 'STRIPE_DICTIA_16_YEARLY',
+    'STRIPE_DICTIA_CLOUD_MONTHLY', 'STRIPE_DICTIA_CLOUD_YEARLY',
+)
+
+
+def _clear_stripe_env():
+    for k in _PRICE_ENV_VARS:
+        os.environ.pop(k, None)
+    # Reset stripe module-level api_key state
+    import stripe
+    stripe.api_key = None
+
+
+def _disable_csrf():
+    app.config['WTF_CSRF_ENABLED'] = False
+
+
+def _make_user(email='checkout@example.qc.ca', password='Password!123',
+               username=None, name='Checkout User',
+               stripe_customer_id=None):
+    hashed = bcrypt.generate_password_hash(password).decode('utf-8')
+    u = User(
+        username=username or email.split('@', 1)[0][:20],
+        email=email,
+        password=hashed,
+        email_verified=True,
+        name=name,
+        stripe_customer_id=stripe_customer_id,
+    )
+    db.session.add(u)
+    db.session.commit()
+    return u
+
+
+def _login_session(client, user):
+    with client.session_transaction() as sess:
+        sess['_user_id'] = str(user.id)
+        sess['_fresh'] = True
+
+
+# ----------------------------------------------------------------------
+# 1-2. is_stripe_configured
+# ----------------------------------------------------------------------
+
+def test_is_stripe_configured_when_env_set():
+    _clear_stripe_env()
+    try:
+        os.environ['STRIPE_SECRET_KEY'] = 'sk_test_fake'
+        from src.billing.stripe_client import is_stripe_configured
+        assert is_stripe_configured() is True
+    finally:
+        _clear_stripe_env()
+
+
+def test_is_stripe_configured_when_env_unset():
+    _clear_stripe_env()
+    try:
+        from src.billing.stripe_client import is_stripe_configured
+        assert is_stripe_configured() is False
+    finally:
+        _clear_stripe_env()
+
+
+# ----------------------------------------------------------------------
+# 3-4. get_plan
+# ----------------------------------------------------------------------
+
+def test_get_plan_returns_known_plan():
+    from src.billing.plans import get_plan, Plan
+    plan = get_plan('dictia-cloud')
+    assert plan is not None
+    assert isinstance(plan, Plan)
+    assert plan.slug == 'dictia-cloud'
+    assert plan.has_setup_fee is False
+
+
+def test_get_plan_returns_none_for_unknown():
+    from src.billing.plans import get_plan
+    assert get_plan('foo') is None
+    assert get_plan('') is None
+
+
+# ----------------------------------------------------------------------
+# 5-7. Plan.is_configured
+# ----------------------------------------------------------------------
+
+def test_plan_is_configured_when_env_set():
+    _clear_stripe_env()
+    try:
+        os.environ['STRIPE_DICTIA_CLOUD_MONTHLY'] = 'price_cloud_m'
+        os.environ['STRIPE_DICTIA_CLOUD_YEARLY'] = 'price_cloud_y'
+        from src.billing.plans import get_plan
+        assert get_plan('dictia-cloud').is_configured() is True
+    finally:
+        _clear_stripe_env()
+
+
+def test_plan_is_not_configured_when_env_missing():
+    _clear_stripe_env()
+    try:
+        from src.billing.plans import get_plan
+        assert get_plan('dictia-cloud').is_configured() is False
+    finally:
+        _clear_stripe_env()
+
+
+def test_hardware_plan_requires_setup_env():
+    _clear_stripe_env()
+    try:
+        os.environ['STRIPE_DICTIA_8_MONTHLY'] = 'price_8_m'
+        os.environ['STRIPE_DICTIA_8_YEARLY'] = 'price_8_y'
+        # NO STRIPE_DICTIA_8_SETUP
+        from src.billing.plans import get_plan
+        assert get_plan('dictia-8').is_configured() is False
+        os.environ['STRIPE_DICTIA_8_SETUP'] = 'price_8_setup'
+        assert get_plan('dictia-8').is_configured() is True
+    finally:
+        _clear_stripe_env()
+
+
+# ----------------------------------------------------------------------
+# 8-9. get_or_create_customer
+# ----------------------------------------------------------------------
+
+def test_get_or_create_customer_creates_when_missing():
+    with app.app_context():
+        _clear_stripe_env()
+        os.environ['STRIPE_SECRET_KEY'] = 'sk_test_fake'
+        db.create_all()
+        try:
+            user = _make_user(email='newcust@example.qc.ca', name='Alice')
+            assert user.stripe_customer_id is None
+            with patch('src.billing.stripe_client.stripe.Customer.create') as mock_cust:
+                mock_cust.return_value = MagicMock(id='cus_fakeNEW')
+                from src.billing.stripe_client import get_or_create_customer
+                cust_id = get_or_create_customer(user)
+            assert cust_id == 'cus_fakeNEW'
+            mock_cust.assert_called_once()
+            kwargs = mock_cust.call_args.kwargs
+            assert kwargs['email'] == 'newcust@example.qc.ca'
+            assert kwargs['name'] == 'Alice'
+            assert kwargs['metadata']['dictia_user_id'] == str(user.id)
+            db.session.refresh(user)
+            assert user.stripe_customer_id == 'cus_fakeNEW'
+        finally:
+            db.session.rollback()
+            db.drop_all()
+            _clear_stripe_env()
+
+
+def test_get_or_create_customer_reuses_existing():
+    with app.app_context():
+        _clear_stripe_env()
+        os.environ['STRIPE_SECRET_KEY'] = 'sk_test_fake'
+        db.create_all()
+        try:
+            user = _make_user(email='oldcust@example.qc.ca',
+                              stripe_customer_id='cus_existing')
+            with patch('src.billing.stripe_client.stripe.Customer.create') as mock_cust:
+                from src.billing.stripe_client import get_or_create_customer
+                cust_id = get_or_create_customer(user)
+            assert cust_id == 'cus_existing'
+            mock_cust.assert_not_called()
+        finally:
+            db.session.rollback()
+            db.drop_all()
+            _clear_stripe_env()
+
+
+# ----------------------------------------------------------------------
+# 10-13. create_checkout_session
+# ----------------------------------------------------------------------
+
+def test_create_checkout_session_includes_setup_for_hardware_plan():
+    with app.app_context():
+        _clear_stripe_env()
+        os.environ['STRIPE_SECRET_KEY'] = 'sk_test_fake'
+        os.environ['STRIPE_DICTIA_8_SETUP'] = 'price_setup'
+        os.environ['STRIPE_DICTIA_8_MONTHLY'] = 'price_8m'
+        os.environ['STRIPE_DICTIA_8_YEARLY'] = 'price_8y'
+        db.create_all()
+        try:
+            user = _make_user(email='hwsetup@example.qc.ca', name='Bob')
+            with patch('src.billing.stripe_client.stripe.Customer.create') as mock_cust, \
+                 patch('src.billing.stripe_client.stripe.checkout.Session.create') as mock_sess:
+                mock_cust.return_value = MagicMock(id='cus_x')
+                mock_sess.return_value = MagicMock(url='https://checkout.stripe.test/cs_x')
+                from src.billing.stripe_client import create_checkout_session
+                create_checkout_session(
+                    plan_slug='dictia-8', period='monthly', user=user,
+                    success_url='https://x.ca/success', cancel_url='https://x.ca/cancel',
+                )
+                kwargs = mock_sess.call_args.kwargs
+                assert len(kwargs['line_items']) == 2
+                assert kwargs['line_items'][0]['price'] == 'price_setup'
+                assert kwargs['line_items'][1]['price'] == 'price_8m'
+                assert kwargs['mode'] == 'subscription'
+                assert kwargs['currency'] == 'cad'
+                assert kwargs['automatic_tax']['enabled'] is True
+                assert kwargs['allow_promotion_codes'] is True
+                assert kwargs['billing_address_collection'] == 'required'
+                # success_url must include CHECKOUT_SESSION_ID placeholder
+                assert '{CHECKOUT_SESSION_ID}' in kwargs['success_url']
+        finally:
+            db.session.rollback()
+            db.drop_all()
+            _clear_stripe_env()
+
+
+def test_create_checkout_session_no_setup_for_cloud_plan():
+    with app.app_context():
+        _clear_stripe_env()
+        os.environ['STRIPE_SECRET_KEY'] = 'sk_test_fake'
+        os.environ['STRIPE_DICTIA_CLOUD_MONTHLY'] = 'price_cm'
+        os.environ['STRIPE_DICTIA_CLOUD_YEARLY'] = 'price_cy'
+        db.create_all()
+        try:
+            user = _make_user(email='cloudplan@example.qc.ca', name='Carol')
+            with patch('src.billing.stripe_client.stripe.Customer.create') as mock_cust, \
+                 patch('src.billing.stripe_client.stripe.checkout.Session.create') as mock_sess:
+                mock_cust.return_value = MagicMock(id='cus_y')
+                mock_sess.return_value = MagicMock(url='https://x/cs_y')
+                from src.billing.stripe_client import create_checkout_session
+                create_checkout_session(
+                    plan_slug='dictia-cloud', period='monthly', user=user,
+                    success_url='https://x.ca/success', cancel_url='https://x.ca/cancel',
+                )
+                kwargs = mock_sess.call_args.kwargs
+                assert len(kwargs['line_items']) == 1
+                assert kwargs['line_items'][0]['price'] == 'price_cm'
+        finally:
+            db.session.rollback()
+            db.drop_all()
+            _clear_stripe_env()
+
+
+def test_create_checkout_session_uses_yearly_price_when_period_yearly():
+    with app.app_context():
+        _clear_stripe_env()
+        os.environ['STRIPE_SECRET_KEY'] = 'sk_test_fake'
+        os.environ['STRIPE_DICTIA_CLOUD_MONTHLY'] = 'price_cm'
+        os.environ['STRIPE_DICTIA_CLOUD_YEARLY'] = 'price_cy'
+        db.create_all()
+        try:
+            user = _make_user(email='yearly@example.qc.ca', name='Dan')
+            with patch('src.billing.stripe_client.stripe.Customer.create') as mock_cust, \
+                 patch('src.billing.stripe_client.stripe.checkout.Session.create') as mock_sess:
+                mock_cust.return_value = MagicMock(id='cus_z')
+                mock_sess.return_value = MagicMock(url='https://x/cs_z')
+                from src.billing.stripe_client import create_checkout_session
+                create_checkout_session(
+                    plan_slug='dictia-cloud', period='yearly', user=user,
+                    success_url='https://x.ca/success', cancel_url='https://x.ca/cancel',
+                )
+                kwargs = mock_sess.call_args.kwargs
+                assert kwargs['line_items'][0]['price'] == 'price_cy'
+        finally:
+            db.session.rollback()
+            db.drop_all()
+            _clear_stripe_env()
+
+
+def test_create_checkout_session_includes_metadata():
+    with app.app_context():
+        _clear_stripe_env()
+        os.environ['STRIPE_SECRET_KEY'] = 'sk_test_fake'
+        os.environ['STRIPE_DICTIA_CLOUD_MONTHLY'] = 'price_cm'
+        os.environ['STRIPE_DICTIA_CLOUD_YEARLY'] = 'price_cy'
+        db.create_all()
+        try:
+            user = _make_user(email='meta@example.qc.ca', name='Eve')
+            with patch('src.billing.stripe_client.stripe.Customer.create') as mock_cust, \
+                 patch('src.billing.stripe_client.stripe.checkout.Session.create') as mock_sess:
+                mock_cust.return_value = MagicMock(id='cus_q')
+                mock_sess.return_value = MagicMock(url='https://x/cs_q')
+                from src.billing.stripe_client import create_checkout_session
+                create_checkout_session(
+                    plan_slug='dictia-cloud', period='monthly', user=user,
+                    success_url='https://x.ca/success', cancel_url='https://x.ca/cancel',
+                )
+                kwargs = mock_sess.call_args.kwargs
+                meta = kwargs['metadata']
+                assert meta['dictia_user_id'] == str(user.id)
+                assert meta['dictia_plan_slug'] == 'dictia-cloud'
+                assert meta['dictia_period'] == 'monthly'
+                # Subscription-level metadata too (used by webhook B-2.8)
+                sub_meta = kwargs['subscription_data']['metadata']
+                assert sub_meta['dictia_user_id'] == str(user.id)
+                assert sub_meta['dictia_plan_slug'] == 'dictia-cloud'
+                assert sub_meta['dictia_period'] == 'monthly'
+        finally:
+            db.session.rollback()
+            db.drop_all()
+            _clear_stripe_env()
+
+
+# ----------------------------------------------------------------------
+# 14-17. create_checkout_session error paths
+# ----------------------------------------------------------------------
+
+def test_create_checkout_session_raises_on_unknown_plan():
+    with app.app_context():
+        _clear_stripe_env()
+        os.environ['STRIPE_SECRET_KEY'] = 'sk_test_fake'
+        db.create_all()
+        try:
+            user = _make_user(email='unkplan@example.qc.ca')
+            from src.billing.stripe_client import create_checkout_session
+            try:
+                create_checkout_session(
+                    plan_slug='foo', period='monthly', user=user,
+                    success_url='https://x/s', cancel_url='https://x/c',
+                )
+                raise AssertionError('Expected ValueError')
+            except ValueError:
+                pass
+        finally:
+            db.session.rollback()
+            db.drop_all()
+            _clear_stripe_env()
+
+
+def test_create_checkout_session_raises_on_invalid_period():
+    with app.app_context():
+        _clear_stripe_env()
+        os.environ['STRIPE_SECRET_KEY'] = 'sk_test_fake'
+        os.environ['STRIPE_DICTIA_CLOUD_MONTHLY'] = 'price_cm'
+        os.environ['STRIPE_DICTIA_CLOUD_YEARLY'] = 'price_cy'
+        db.create_all()
+        try:
+            user = _make_user(email='badperiod@example.qc.ca')
+            from src.billing.stripe_client import create_checkout_session
+            try:
+                create_checkout_session(
+                    plan_slug='dictia-cloud', period='quarterly', user=user,
+                    success_url='https://x/s', cancel_url='https://x/c',
+                )
+                raise AssertionError('Expected ValueError')
+            except ValueError:
+                pass
+        finally:
+            db.session.rollback()
+            db.drop_all()
+            _clear_stripe_env()
+
+
+def test_create_checkout_session_raises_when_stripe_not_configured():
+    with app.app_context():
+        _clear_stripe_env()
+        # NO STRIPE_SECRET_KEY
+        db.create_all()
+        try:
+            user = _make_user(email='nokey@example.qc.ca')
+            from src.billing.stripe_client import (
+                create_checkout_session, StripeNotConfiguredError,
+            )
+            try:
+                create_checkout_session(
+                    plan_slug='dictia-cloud', period='monthly', user=user,
+                    success_url='https://x/s', cancel_url='https://x/c',
+                )
+                raise AssertionError('Expected StripeNotConfiguredError')
+            except StripeNotConfiguredError:
+                pass
+        finally:
+            db.session.rollback()
+            db.drop_all()
+            _clear_stripe_env()
+
+
+def test_create_checkout_session_raises_when_plan_env_missing():
+    with app.app_context():
+        _clear_stripe_env()
+        os.environ['STRIPE_SECRET_KEY'] = 'sk_test_fake'
+        # NO price IDs for dictia-cloud
+        db.create_all()
+        try:
+            user = _make_user(email='noprice@example.qc.ca')
+            from src.billing.stripe_client import (
+                create_checkout_session, StripeNotConfiguredError,
+            )
+            try:
+                create_checkout_session(
+                    plan_slug='dictia-cloud', period='monthly', user=user,
+                    success_url='https://x/s', cancel_url='https://x/c',
+                )
+                raise AssertionError('Expected StripeNotConfiguredError')
+            except StripeNotConfiguredError:
+                pass
+        finally:
+            db.session.rollback()
+            db.drop_all()
+            _clear_stripe_env()
+
+
+# ----------------------------------------------------------------------
+# 18-22. /checkout/<plan> route
+# ----------------------------------------------------------------------
+
+def test_checkout_route_redirects_to_stripe_url():
+    with app.app_context():
+        _disable_csrf()
+        _clear_stripe_env()
+        os.environ['STRIPE_SECRET_KEY'] = 'sk_test_fake'
+        os.environ['STRIPE_DICTIA_CLOUD_MONTHLY'] = 'price_cm'
+        os.environ['STRIPE_DICTIA_CLOUD_YEARLY'] = 'price_cy'
+        db.create_all()
+        try:
+            user = _make_user(email='rt-redir@example.qc.ca', name='Frank')
+            with app.test_client() as client:
+                _login_session(client, user)
+                with patch('src.billing.routes.create_checkout_session') as mock_create:
+                    mock_create.return_value = MagicMock(
+                        url='https://checkout.stripe.test/cs_redir'
+                    )
+                    resp = client.get('/checkout/dictia-cloud?period=monthly',
+                                      follow_redirects=False)
+                assert resp.status_code == 303
+                assert resp.headers['Location'] == 'https://checkout.stripe.test/cs_redir'
+                # Ensure routes called the helper with the right args
+                mock_create.assert_called_once()
+                call_kwargs = mock_create.call_args.kwargs
+                assert call_kwargs['plan_slug'] == 'dictia-cloud'
+                assert call_kwargs['period'] == 'monthly'
+        finally:
+            db.session.rollback()
+            db.drop_all()
+            _clear_stripe_env()
+
+
+def test_checkout_route_unknown_plan_redirects_to_tarifs():
+    with app.app_context():
+        _disable_csrf()
+        _clear_stripe_env()
+        os.environ['STRIPE_SECRET_KEY'] = 'sk_test_fake'
+        db.create_all()
+        try:
+            user = _make_user(email='rt-unk@example.qc.ca')
+            with app.test_client() as client:
+                _login_session(client, user)
+                resp = client.get('/checkout/foo', follow_redirects=False)
+                assert resp.status_code == 302
+                assert '/tarifs' in resp.headers['Location']
+        finally:
+            db.session.rollback()
+            db.drop_all()
+            _clear_stripe_env()
+
+
+def test_checkout_route_normalizes_invalid_period_to_monthly():
+    with app.app_context():
+        _disable_csrf()
+        _clear_stripe_env()
+        os.environ['STRIPE_SECRET_KEY'] = 'sk_test_fake'
+        os.environ['STRIPE_DICTIA_CLOUD_MONTHLY'] = 'price_cm'
+        os.environ['STRIPE_DICTIA_CLOUD_YEARLY'] = 'price_cy'
+        db.create_all()
+        try:
+            user = _make_user(email='rt-period@example.qc.ca')
+            with app.test_client() as client:
+                _login_session(client, user)
+                with patch('src.billing.routes.create_checkout_session') as mock_create:
+                    mock_create.return_value = MagicMock(
+                        url='https://checkout.stripe.test/cs_norm'
+                    )
+                    resp = client.get('/checkout/dictia-cloud?period=quarterly',
+                                      follow_redirects=False)
+                assert resp.status_code == 303
+                assert mock_create.call_args.kwargs['period'] == 'monthly'
+        finally:
+            db.session.rollback()
+            db.drop_all()
+            _clear_stripe_env()
+
+
+def test_checkout_route_requires_login():
+    with app.app_context():
+        _disable_csrf()
+        _clear_stripe_env()
+        db.create_all()
+        try:
+            with app.test_client() as client:
+                resp = client.get('/checkout/dictia-cloud',
+                                  follow_redirects=False)
+                assert resp.status_code == 302
+                assert '/login' in resp.headers['Location']
+        finally:
+            db.session.rollback()
+            db.drop_all()
+            _clear_stripe_env()
+
+
+def test_checkout_route_friendly_message_when_stripe_not_configured():
+    with app.app_context():
+        _disable_csrf()
+        _clear_stripe_env()
+        # NO STRIPE_SECRET_KEY
+        db.create_all()
+        try:
+            user = _make_user(email='rt-noconfig@example.qc.ca')
+            with app.test_client() as client:
+                _login_session(client, user)
+                resp = client.get('/checkout/dictia-cloud',
+                                  follow_redirects=False)
+                assert resp.status_code == 302
+                assert '/tarifs' in resp.headers['Location']
+                # Follow the redirect to see the flashed message
+                resp2 = client.get('/tarifs')
+                body = resp2.get_data(as_text=True)
+                assert 'info@dictia.ca' in body
+        finally:
+            db.session.rollback()
+            db.drop_all()
+            _clear_stripe_env()
+
+
+# ----------------------------------------------------------------------
+# 23-24. /checkout/success and /checkout/cancel
+# ----------------------------------------------------------------------
+
+def test_success_route_renders_template():
+    with app.app_context():
+        _disable_csrf()
+        db.create_all()
+        try:
+            with app.test_client() as client:
+                resp = client.get('/checkout/success?session_id=cs_test_abc')
+                assert resp.status_code == 200
+                body = resp.get_data(as_text=True)
+                # Body should mention the async-activation note (per spec)
+                assert 'minutes' in body.lower() or 'activé' in body.lower() \
+                    or 'activée' in body.lower() or 'confirmé' in body.lower()
+        finally:
+            db.session.rollback()
+            db.drop_all()
+
+
+def test_cancel_route_renders_template():
+    with app.app_context():
+        _disable_csrf()
+        db.create_all()
+        try:
+            with app.test_client() as client:
+                resp = client.get('/checkout/cancel')
+                assert resp.status_code == 200
+                body = resp.get_data(as_text=True)
+                # "no charge made" reassurance in French
+                assert 'aucun' in body.lower() or 'annulé' in body.lower()
+        finally:
+            db.session.rollback()
+            db.drop_all()
+
+
+# ----------------------------------------------------------------------
+# 25. Integration with no-crawl headers
+# ----------------------------------------------------------------------
+
+def test_success_route_in_public_indexable_endpoints():
+    """Defensive: 'billing.success' was added to _PUBLIC_INDEXABLE_ENDPOINTS in B-1.3."""
+    from src.app import _PUBLIC_INDEXABLE_ENDPOINTS
+    assert 'billing.success' in _PUBLIC_INDEXABLE_ENDPOINTS