Add explicit test for function auth levels

tests/smoke/test_function_app.py

@@ -0,0 +1,29 @@
+"""Smoke tests for the function app module."""
+
+import inspect
+import json
+
+import function_app
+from azure.functions.decorators import function_app as azure_function_app
+
+
+def get_function_auth_level(
+    function: azure_function_app.FunctionBuilder,
+) -> str:
+    """Gets the auth level of a function."""
+    settings = json.loads(function._function.get_function_json())
+    return settings["bindings"][0]["authLevel"]
+
+
+def test_function_auth_level() -> None:
+    """Tests that no function has the anonymous auth level."""
+    endpoints = inspect.getmembers(
+        function_app,
+        lambda attribute: isinstance(attribute, azure_function_app.FunctionBuilder),
+    )
+    allowed_auth_levels = ["FUNCTION", "ADMIN"]
+
+    for name, endpoint in endpoints:
+        auth_level = get_function_auth_level(endpoint)
+
+        assert auth_level in allowed_auth_levels, f"{name} has the wrong auth level."