Add Settings subclasses to all services and auto-discovered init tests

- Add dedicated Settings subclasses to 20 LLM services that were
  borrowing parent Settings classes (e.g. AzureLLMSettings,
  GroqLLMSettings) so users don't need cross-module imports
- Fix field defaults to NOT_GIVEN in BaseWhisperSTTSettings,
  OpenAIRealtimeSTTSettings, and NvidiaSegmentedSTTSettings for
  delta-mode safety
- Fix incomplete default_settings in AWS, Cartesia, ElevenLabs,
  Fish, and Whisper services so validate_complete() passes
- Add auto-discovered tests that verify all Settings classes default
  to NOT_GIVEN (delta safety) and all services initialize with
  complete settings (store completeness)

tests/test_service_init.py

@@ -0,0 +1,181 @@
+#
+# Copyright (c) 2024-2026, Daily
+#
+# SPDX-License-Identifier: BSD 2-Clause License
+#
+
+"""Tests for service settings and initialization patterns.
+
+Settings objects operate in two modes:
+
+- **Store mode** (``self._settings``): the live state inside a service.
+  Every field must hold a real value (``None`` is fine, ``NOT_GIVEN`` is not).
+- **Delta mode** (``FooSettings()`` with no args): a sparse update.
+  Every field must default to ``NOT_GIVEN`` so ``apply_update()`` skips
+  untouched fields and doesn't accidentally overwrite the store.
+
+These tests verify both sides of that contract automatically:
+
+1. **Delta defaults** — Instantiate every ``ServiceSettings`` subclass with
+   no arguments and assert that every field is ``NOT_GIVEN``.  Catches the
+   bug where a field defaults to ``None`` instead of ``NOT_GIVEN``, which
+   would cause partial deltas to silently overwrite unrelated store values.
+
+2. **Store completeness** — Instantiate every concrete service with dummy
+   args and assert that ``_settings`` contains no ``NOT_GIVEN`` values.
+   This is the same check that ``validate_complete()`` runs in ``start()``,
+   but caught here at unit-test time without needing a running pipeline.
+   Catches services that forget to initialize a field in ``default_settings``.
+
+All Settings and Service classes are auto-discovered via ``pkgutil``;
+new services are covered automatically with no per-service maintenance.
+"""
+
+import importlib
+import inspect
+import pkgutil
+import warnings
+from dataclasses import fields
+
+import pytest
+
+import pipecat.services
+from pipecat.services.ai_service import AIService
+from pipecat.services.settings import ServiceSettings, is_given
+
+# Modules that define abstract base service classes (not concrete services).
+_BASE_MODULES = frozenset(
+    {
+        "pipecat.services.ai_service",
+        "pipecat.services.llm_service",
+        "pipecat.services.stt_service",
+        "pipecat.services.tts_service",
+        "pipecat.services.image_gen_service",
+        "pipecat.services.vision_service",
+    }
+)
+
+
+# ---------------------------------------------------------------------------
+# Auto-discovery
+# ---------------------------------------------------------------------------
+
+
+def _all_subclasses(cls):
+    result = set()
+    for sub in cls.__subclasses__():
+        result.add(sub)
+        result.update(_all_subclasses(sub))
+    return result
+
+
+def _import_all_service_modules():
+    """Import every module under pipecat.services (skipping missing deps)."""
+    package = pipecat.services
+    for _importer, modname, _ispkg in pkgutil.walk_packages(
+        package.__path__, prefix=package.__name__ + "."
+    ):
+        try:
+            importlib.import_module(modname)
+        except Exception:
+            continue
+
+
+_import_all_service_modules()
+
+ALL_SETTINGS_CLASSES = sorted(_all_subclasses(ServiceSettings), key=lambda c: c.__qualname__)
+assert ALL_SETTINGS_CLASSES, "No settings classes discovered"
+
+
+# ---------------------------------------------------------------------------
+# Service instantiation helpers
+# ---------------------------------------------------------------------------
+
+
+def _try_instantiate(cls):
+    """Try to instantiate a service with dummy values for required args.
+
+    Inspects the __init__ signature and passes "test" for every required
+    keyword-only parameter.  Services that need non-string required args
+    or fail for other reasons will raise and be skipped by the test.
+    """
+    sig = inspect.signature(cls.__init__)
+    kwargs = {}
+    for name, param in sig.parameters.items():
+        if name == "self":
+            continue
+        if param.kind in (param.VAR_POSITIONAL, param.VAR_KEYWORD):
+            continue
+        if param.default is not param.empty:
+            continue
+        # Required parameter — pass a dummy string
+        kwargs[name] = "test"
+    return cls(**kwargs)
+
+
+def _discover_service_classes():
+    """Return concrete service classes that can be instantiated with dummy args."""
+    result = []
+    for cls in sorted(_all_subclasses(AIService), key=lambda c: c.__qualname__):
+        # Skip abstract base classes defined in framework modules.
+        if cls.__module__ in _BASE_MODULES:
+            continue
+        try:
+            svc = _try_instantiate(cls)
+        except Exception:
+            continue
+        if hasattr(svc, "_settings"):
+            result.append(cls)
+    return result
+
+
+ALL_SERVICE_CLASSES = _discover_service_classes()
+assert ALL_SERVICE_CLASSES, "No service classes could be instantiated"
+
+
+# ---------------------------------------------------------------------------
+# 1. Settings defaults: delta-mode safety
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.parametrize("settings_cls", ALL_SETTINGS_CLASSES, ids=lambda c: c.__qualname__)
+def test_delta_defaults_are_not_given(settings_cls):
+    """Every field must default to NOT_GIVEN so empty deltas are no-ops.
+
+    A field that defaults to None instead of NOT_GIVEN will cause
+    apply_update() to overwrite the corresponding store value whenever
+    a partial delta is applied.
+    """
+    instance = settings_cls()
+    for f in fields(instance):
+        if f.name == "extra":
+            continue
+        val = getattr(instance, f.name)
+        assert not is_given(val), (
+            f"{settings_cls.__qualname__}.{f.name} defaults to {val!r}, expected NOT_GIVEN"
+        )
+
+
+# ---------------------------------------------------------------------------
+# 2. Service construction: store-mode completeness
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.parametrize("service_cls", ALL_SERVICE_CLASSES, ids=lambda c: c.__qualname__)
+def test_service_settings_complete(service_cls):
+    """After construction, _settings must have no NOT_GIVEN values.
+
+    This is what validate_complete() checks in start().  Catching it
+    here means we don't need a running pipeline to find missing defaults.
+    """
+    try:
+        svc = _try_instantiate(service_cls)
+    except Exception:
+        pytest.skip("Cannot re-instantiate (environment issue)")
+    for f in fields(svc._settings):
+        if f.name == "extra":
+            continue
+        val = getattr(svc._settings, f.name)
+        assert is_given(val), (
+            f"{service_cls.__qualname__}._settings.{f.name} is NOT_GIVEN after construction"
+        )