refactor: improve app initialization and update rate limiter tests for consistency

backend/app/__init__.py

@@ -1,4 +1,5 @@
 """Flask Application Factory."""
+
 import os
 
 from flask import Flask, jsonify
@@ -11,7 +12,12 @@ from app.services.ai_cost_service import init_ai_cost_db
 from app.services.site_assistant_service import init_site_assistant_db
 from app.services.contact_service import init_contact_db
 from app.services.stripe_service import init_stripe_db
-from app.utils.csrf import CSRFError, apply_csrf_cookie, should_enforce_csrf, validate_csrf_request
+from app.utils.csrf import (
+    CSRFError,
+    apply_csrf_cookie,
+    should_enforce_csrf,
+    validate_csrf_request,
+)
 
 
 def _init_sentry(app):
@@ -35,13 +41,15 @@ def _init_sentry(app):
         app.logger.warning("sentry-sdk not installed — monitoring disabled.")
 
 
-def create_app(config_name=None):
+def create_app(config_name=None, config_overrides=None):
     """Create and configure the Flask application."""
     if config_name is None:
         config_name = os.getenv("FLASK_ENV", "development")
 
     app = Flask(__name__)
     app.config.from_object(config[config_name])
+    if config_overrides:
+        app.config.update(config_overrides)
 
     # Initialize Sentry early
     _init_sentry(app)

backend/tests/test_rate_limiter.py

@@ -1,6 +1,8 @@
 """Tests for rate limiting middleware."""
+
 import pytest
 from app import create_app
+from tests.conftest import CSRFTestClient
 
 
 @pytest.fixture
@@ -11,33 +13,24 @@ def rate_limited_app(tmp_path):
     never throttled.  Here we force the extension's internal flag back to
     True *after* init_app so the decorator limits are enforced.
     """
-    app = create_app('testing')
-    app.config.update({
-        'TESTING': True,
-        'RATELIMIT_STORAGE_URI': 'memory://',
-        'UPLOAD_FOLDER': str(tmp_path / 'uploads'),
-        'OUTPUT_FOLDER': str(tmp_path / 'outputs'),
-    })
+    app = create_app(
+        "testing",
+        {
+            "TESTING": True,
+            "RATELIMIT_ENABLED": True,
+            "RATELIMIT_STORAGE_URI": "memory://",
+            "UPLOAD_FOLDER": str(tmp_path / "uploads"),
+            "OUTPUT_FOLDER": str(tmp_path / "outputs"),
+        },
+    )
+    app.test_client_class = CSRFTestClient
     import os
-    os.makedirs(app.config['UPLOAD_FOLDER'], exist_ok=True)
-    os.makedirs(app.config['OUTPUT_FOLDER'], exist_ok=True)
 
-    # flask-limiter 3.x returns from init_app immediately when
-    # RATELIMIT_ENABLED=False (TestingConfig default), so `initialized`
-    # stays False and no limits are enforced.  We override the config key
-    # and call init_app a SECOND time so the extension fully initialises.
-    # It is safe to call twice — flask-limiter guards against duplicate
-    # before_request hook registration via app.extensions["limiter"].
-    from app.extensions import limiter as _limiter
-    app.config['RATELIMIT_ENABLED'] = True
-    _limiter.init_app(app)        # second call — now RATELIMIT_ENABLED=True
+    os.makedirs(app.config["UPLOAD_FOLDER"], exist_ok=True)
+    os.makedirs(app.config["OUTPUT_FOLDER"], exist_ok=True)
 
     yield app
 
-    # Restore so other tests are unaffected
-    _limiter.enabled = False
-    _limiter.initialized = False
-
 
 @pytest.fixture
 def rate_limited_client(rate_limited_app):
@@ -48,12 +41,12 @@ class TestRateLimiter:
     def test_health_endpoint_not_rate_limited(self, client):
         """Health endpoint should handle many rapid requests."""
         for _ in range(20):
-            response = client.get('/api/health')
+            response = client.get("/api/health")
             assert response.status_code == 200
 
     def test_rate_limit_header_present(self, client):
         """Response should include a valid HTTP status code."""
-        response = client.get('/api/health')
+        response = client.get("/api/health")
         assert response.status_code == 200
 
 
@@ -68,7 +61,7 @@ class TestRateLimitEnforcement:
         """
         blocked = False
         for i in range(15):
-            r = rate_limited_client.post('/api/compress/pdf')
+            r = rate_limited_client.post("/api/compress/pdf")
             if r.status_code == 429:
                 blocked = True
                 break
@@ -81,7 +74,7 @@ class TestRateLimitEnforcement:
         """POST /api/convert/pdf-to-word is also rate-limited."""
         blocked = False
         for _ in range(15):
-            r = rate_limited_client.post('/api/convert/pdf-to-word')
+            r = rate_limited_client.post("/api/convert/pdf-to-word")
             if r.status_code == 429:
                 blocked = True
                 break
@@ -94,8 +87,8 @@ class TestRateLimitEnforcement:
         """
         # Exhaust compress limit
         for _ in range(15):
-            rate_limited_client.post('/api/compress/pdf')
+            rate_limited_client.post("/api/compress/pdf")
 
         # Health should still respond normally
-        r = rate_limited_client.get('/api/health')
-        assert r.status_code == 200
+        r = rate_limited_client.get("/api/health")
+        assert r.status_code == 200