diff --git a/pyproject.toml b/pyproject.toml
index a03038f..2ddb9e0 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -37,6 +37,10 @@ explicit_package_bases = true
 module = "pytest"
 ignore_missing_imports = true
 
+[[tool.mypy.overrides]]
+module = "fakeredis"
+ignore_missing_imports = true
+
 [tool.pytest.ini_options]
 testpaths = ["tests"]
 addopts = "-v --tb=short"
diff --git a/src/__init__.py b/src/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/src/app.py b/src/app.py
new file mode 100644
index 0000000..a981949
--- /dev/null
+++ b/src/app.py
@@ -0,0 +1,22 @@
+from flask import Flask
+
+from src.queue.handler import QueueHandler
+
+
+def create_app() -> Flask:
+    """Erstellt und konfiguriert die Flask-App."""
+    app = Flask(__name__)
+    app.config.from_mapping(
+        REDIS_HOST="localhost",
+        REDIS_PORT=6379,
+    )
+    app.queue_handler = QueueHandler(  # type: ignore[attr-defined]
+        redis_host=app.config["REDIS_HOST"],
+        redis_port=app.config["REDIS_PORT"],
+    )
+
+    @app.route("/health")
+    def health() -> dict[str, object]:
+        return {"status": "ok", "queue_size": app.queue_handler.queue_size()}  # type: ignore[attr-defined]
+
+    return app
diff --git a/tests/test_app.py b/tests/test_app.py
new file mode 100644
index 0000000..246751e
--- /dev/null
+++ b/tests/test_app.py
@@ -0,0 +1,62 @@
+"""Tests für die Flask-App-Factory mit fakeredis."""
+
+from __future__ import annotations
+
+import fakeredis
+from flask import Flask
+from flask.testing import FlaskClient
+
+from src.app import create_app
+from src.queue.handler import QueueHandler
+
+
+def test_create_app_returns_flask_app() -> None:
+    """create_app() liefert eine Flask-App-Instanz zurück."""
+    app = create_app()
+    assert isinstance(app, Flask)
+
+
+def test_health_returns_status_ok() -> None:
+    """GET /health liefert 200 und JSON mit status=ok."""
+    app = create_app()
+
+    # QueueHandler mit fakeredis ersetzen
+    fake_redis = fakeredis.FakeRedis(decode_responses=True)
+    qh = QueueHandler.__new__(QueueHandler)
+    qh.redis = fake_redis
+    qh.stream_key = "bsn:submissions"
+    qh.processed_set = "bsn:processed"
+    qh.stream_ids_hash = "bsn:stream_ids"
+    qh.group_name = "bsn-workers"
+    qh._ensure_consumer_group()
+    app.queue_handler = qh  # type: ignore[attr-defined]
+
+    client: FlaskClient = app.test_client()
+    response = client.get("/health")
+    assert response.status_code == 200
+    data = response.get_json()
+    assert data is not None
+    assert data["status"] == "ok"
+
+
+def test_health_queue_size_is_integer() -> None:
+    """GET /health liefert queue_size als Integer."""
+    app = create_app()
+
+    # QueueHandler mit fakeredis ersetzen
+    fake_redis = fakeredis.FakeRedis(decode_responses=True)
+    qh = QueueHandler.__new__(QueueHandler)
+    qh.redis = fake_redis
+    qh.stream_key = "bsn:submissions"
+    qh.processed_set = "bsn:processed"
+    qh.stream_ids_hash = "bsn:stream_ids"
+    qh.group_name = "bsn-workers"
+    qh._ensure_consumer_group()
+    app.queue_handler = qh  # type: ignore[attr-defined]
+
+    client = app.test_client()
+    response = client.get("/health")
+    assert response.status_code == 200
+    data = response.get_json()
+    assert data is not None
+    assert isinstance(data["queue_size"], int)