refactor(tests): optimize unit test structure

tests/providers/test_litellm_kwargs.py

@@ -0,0 +1,161 @@
+"""Regression tests for PR #2026 — litellm_kwargs injection from ProviderSpec.
+
+Validates that:
+- OpenRouter uses litellm_prefix (NOT custom_llm_provider) to avoid LiteLLM double-prefixing.
+- The litellm_kwargs mechanism works correctly for providers that declare it.
+- Non-gateway providers are unaffected.
+"""
+
+from __future__ import annotations
+
+from types import SimpleNamespace
+from typing import Any
+from unittest.mock import AsyncMock, patch
+
+import pytest
+
+from nanobot.providers.litellm_provider import LiteLLMProvider
+from nanobot.providers.registry import find_by_name
+
+
+def _fake_response(content: str = "ok") -> SimpleNamespace:
+    """Build a minimal acompletion-shaped response object."""
+    message = SimpleNamespace(
+        content=content,
+        tool_calls=None,
+        reasoning_content=None,
+        thinking_blocks=None,
+    )
+    choice = SimpleNamespace(message=message, finish_reason="stop")
+    usage = SimpleNamespace(prompt_tokens=10, completion_tokens=5, total_tokens=15)
+    return SimpleNamespace(choices=[choice], usage=usage)
+
+
+def test_openrouter_spec_uses_prefix_not_custom_llm_provider() -> None:
+    """OpenRouter must rely on litellm_prefix, not custom_llm_provider kwarg.
+
+    LiteLLM internally adds a provider/ prefix when custom_llm_provider is set,
+    which double-prefixes models (openrouter/anthropic/model) and breaks the API.
+    """
+    spec = find_by_name("openrouter")
+    assert spec is not None
+    assert spec.litellm_prefix == "openrouter"
+    assert "custom_llm_provider" not in spec.litellm_kwargs, (
+        "custom_llm_provider causes LiteLLM to double-prefix the model name"
+    )
+
+
+@pytest.mark.asyncio
+async def test_openrouter_prefixes_model_correctly() -> None:
+    """OpenRouter should prefix model as openrouter/vendor/model for LiteLLM routing."""
+    mock_acompletion = AsyncMock(return_value=_fake_response())
+
+    with patch("nanobot.providers.litellm_provider.acompletion", mock_acompletion):
+        provider = LiteLLMProvider(
+            api_key="sk-or-test-key",
+            api_base="https://openrouter.ai/api/v1",
+            default_model="anthropic/claude-sonnet-4-5",
+            provider_name="openrouter",
+        )
+        await provider.chat(
+            messages=[{"role": "user", "content": "hello"}],
+            model="anthropic/claude-sonnet-4-5",
+        )
+
+    call_kwargs = mock_acompletion.call_args.kwargs
+    assert call_kwargs["model"] == "openrouter/anthropic/claude-sonnet-4-5", (
+        "LiteLLM needs openrouter/ prefix to detect the provider and strip it before API call"
+    )
+    assert "custom_llm_provider" not in call_kwargs
+
+
+@pytest.mark.asyncio
+async def test_non_gateway_provider_no_extra_kwargs() -> None:
+    """Standard (non-gateway) providers must NOT inject any litellm_kwargs."""
+    mock_acompletion = AsyncMock(return_value=_fake_response())
+
+    with patch("nanobot.providers.litellm_provider.acompletion", mock_acompletion):
+        provider = LiteLLMProvider(
+            api_key="sk-ant-test-key",
+            default_model="claude-sonnet-4-5",
+        )
+        await provider.chat(
+            messages=[{"role": "user", "content": "hello"}],
+            model="claude-sonnet-4-5",
+        )
+
+    call_kwargs = mock_acompletion.call_args.kwargs
+    assert "custom_llm_provider" not in call_kwargs, (
+        "Standard Anthropic provider should NOT inject custom_llm_provider"
+    )
+
+
+@pytest.mark.asyncio
+async def test_gateway_without_litellm_kwargs_injects_nothing_extra() -> None:
+    """Gateways without litellm_kwargs (e.g. AiHubMix) must not add extra keys."""
+    mock_acompletion = AsyncMock(return_value=_fake_response())
+
+    with patch("nanobot.providers.litellm_provider.acompletion", mock_acompletion):
+        provider = LiteLLMProvider(
+            api_key="sk-aihub-test-key",
+            api_base="https://aihubmix.com/v1",
+            default_model="claude-sonnet-4-5",
+            provider_name="aihubmix",
+        )
+        await provider.chat(
+            messages=[{"role": "user", "content": "hello"}],
+            model="claude-sonnet-4-5",
+        )
+
+    call_kwargs = mock_acompletion.call_args.kwargs
+    assert "custom_llm_provider" not in call_kwargs
+
+
+@pytest.mark.asyncio
+async def test_openrouter_autodetect_by_key_prefix() -> None:
+    """OpenRouter should be auto-detected by sk-or- key prefix even without explicit provider_name."""
+    mock_acompletion = AsyncMock(return_value=_fake_response())
+
+    with patch("nanobot.providers.litellm_provider.acompletion", mock_acompletion):
+        provider = LiteLLMProvider(
+            api_key="sk-or-auto-detect-key",
+            default_model="anthropic/claude-sonnet-4-5",
+        )
+        await provider.chat(
+            messages=[{"role": "user", "content": "hello"}],
+            model="anthropic/claude-sonnet-4-5",
+        )
+
+    call_kwargs = mock_acompletion.call_args.kwargs
+    assert call_kwargs["model"] == "openrouter/anthropic/claude-sonnet-4-5", (
+        "Auto-detected OpenRouter should prefix model for LiteLLM routing"
+    )
+
+
+@pytest.mark.asyncio
+async def test_openrouter_native_model_id_gets_double_prefixed() -> None:
+    """Models like openrouter/free must be double-prefixed so LiteLLM strips one layer.
+
+    openrouter/free is an actual OpenRouter model ID.  LiteLLM strips the first
+    openrouter/ for routing, so we must send openrouter/openrouter/free to ensure
+    the API receives openrouter/free.
+    """
+    mock_acompletion = AsyncMock(return_value=_fake_response())
+
+    with patch("nanobot.providers.litellm_provider.acompletion", mock_acompletion):
+        provider = LiteLLMProvider(
+            api_key="sk-or-test-key",
+            api_base="https://openrouter.ai/api/v1",
+            default_model="openrouter/free",
+            provider_name="openrouter",
+        )
+        await provider.chat(
+            messages=[{"role": "user", "content": "hello"}],
+            model="openrouter/free",
+        )
+
+    call_kwargs = mock_acompletion.call_args.kwargs
+    assert call_kwargs["model"] == "openrouter/openrouter/free", (
+        "openrouter/free must become openrouter/openrouter/free — "
+        "LiteLLM strips one layer so the API receives openrouter/free"
+    )