refactor: break up create_timmy() into testable helpers (#520)

Co-authored-by: Kimi Agent <kimi@timmy.local>
Co-committed-by: Kimi Agent <kimi@timmy.local>

tests/timmy/test_agent.py

@@ -444,6 +444,150 @@ def test_get_effective_ollama_model_walks_fallback_chain():
         assert result == "fb-2"
 
 
+# ── _build_tools_list ─────────────────────────────────────────────────────
+
+
+def test_build_tools_list_empty_when_tools_disabled():
+    """Small models get an empty tools list."""
+    from timmy.agent import _build_tools_list
+
+    result = _build_tools_list(use_tools=False, skip_mcp=False, model_name="llama3.2")
+    assert result == []
+
+
+def test_build_tools_list_includes_toolkit_when_enabled():
+    """Tool-capable models get the full toolkit."""
+    mock_toolkit = MagicMock()
+    with patch("timmy.agent.create_full_toolkit", return_value=mock_toolkit):
+        from timmy.agent import _build_tools_list
+
+        result = _build_tools_list(use_tools=True, skip_mcp=True, model_name="llama3.1")
+        assert mock_toolkit in result
+
+
+def test_build_tools_list_skips_mcp_when_flagged():
+    """skip_mcp=True must not call MCP factories."""
+    mock_toolkit = MagicMock()
+    with (
+        patch("timmy.agent.create_full_toolkit", return_value=mock_toolkit),
+        patch("timmy.mcp_tools.create_gitea_mcp_tools") as mock_gitea,
+        patch("timmy.mcp_tools.create_filesystem_mcp_tools") as mock_fs,
+    ):
+        from timmy.agent import _build_tools_list
+
+        _build_tools_list(use_tools=True, skip_mcp=True, model_name="llama3.1")
+        mock_gitea.assert_not_called()
+        mock_fs.assert_not_called()
+
+
+def test_build_tools_list_includes_mcp_when_not_skipped():
+    """skip_mcp=False should attempt MCP tool creation."""
+    mock_toolkit = MagicMock()
+    with (
+        patch("timmy.agent.create_full_toolkit", return_value=mock_toolkit),
+        patch("timmy.mcp_tools.create_gitea_mcp_tools", return_value=None) as mock_gitea,
+        patch("timmy.mcp_tools.create_filesystem_mcp_tools", return_value=None) as mock_fs,
+    ):
+        from timmy.agent import _build_tools_list
+
+        _build_tools_list(use_tools=True, skip_mcp=False, model_name="llama3.1")
+        mock_gitea.assert_called_once()
+        mock_fs.assert_called_once()
+
+
+# ── _build_prompt ─────────────────────────────────────────────────────────
+
+
+def test_build_prompt_includes_base_prompt():
+    """Prompt should always contain the base system prompt."""
+    from timmy.agent import _build_prompt
+
+    result = _build_prompt(use_tools=False, session_id="test")
+    assert "Timmy" in result
+
+
+def test_build_prompt_appends_memory_context():
+    """Memory context should be appended when available."""
+    mock_memory = MagicMock()
+    mock_memory.get_system_context.return_value = "User prefers dark mode."
+    with patch("timmy.memory_system.memory_system", mock_memory):
+        from timmy.agent import _build_prompt
+
+        result = _build_prompt(use_tools=True, session_id="test")
+        assert "GROUNDED CONTEXT" in result
+        assert "dark mode" in result
+
+
+def test_build_prompt_truncates_long_memory():
+    """Long memory context should be truncated."""
+    mock_memory = MagicMock()
+    mock_memory.get_system_context.return_value = "x" * 10000
+    with patch("timmy.memory_system.memory_system", mock_memory):
+        from timmy.agent import _build_prompt
+
+        result = _build_prompt(use_tools=False, session_id="test")
+        assert "[truncated]" in result
+
+
+def test_build_prompt_survives_memory_failure():
+    """Prompt should fall back to base when memory fails."""
+    mock_memory = MagicMock()
+    mock_memory.get_system_context.side_effect = RuntimeError("db locked")
+    with patch("timmy.memory_system.memory_system", mock_memory):
+        from timmy.agent import _build_prompt
+
+        result = _build_prompt(use_tools=True, session_id="test")
+        assert "Timmy" in result
+        # Memory context should NOT be appended (the db locked error was caught)
+        assert "db locked" not in result
+
+
+# ── _create_ollama_agent ──────────────────────────────────────────────────
+
+
+def test_create_ollama_agent_passes_correct_kwargs():
+    """_create_ollama_agent must pass the expected kwargs to Agent."""
+    with (
+        patch("timmy.agent.Agent") as MockAgent,
+        patch("timmy.agent.Ollama"),
+        patch("timmy.agent.SqliteDb"),
+        patch("timmy.agent._warmup_model", return_value=True),
+    ):
+        from timmy.agent import _create_ollama_agent
+
+        _create_ollama_agent(
+            db_file="test.db",
+            model_name="llama3.1",
+            tools_list=[MagicMock()],
+            full_prompt="test prompt",
+            use_tools=True,
+        )
+        kwargs = MockAgent.call_args.kwargs
+        assert kwargs["description"] == "test prompt"
+        assert kwargs["markdown"] is False
+
+
+def test_create_ollama_agent_none_tools_when_empty():
+    """Empty tools_list should pass tools=None to Agent."""
+    with (
+        patch("timmy.agent.Agent") as MockAgent,
+        patch("timmy.agent.Ollama"),
+        patch("timmy.agent.SqliteDb"),
+        patch("timmy.agent._warmup_model", return_value=True),
+    ):
+        from timmy.agent import _create_ollama_agent
+
+        _create_ollama_agent(
+            db_file="test.db",
+            model_name="llama3.2",
+            tools_list=[],
+            full_prompt="test prompt",
+            use_tools=False,
+        )
+        kwargs = MockAgent.call_args.kwargs
+        assert kwargs["tools"] is None
+
+
 def test_no_hardcoded_fallback_constants_in_agent():
     """agent.py must not define module-level DEFAULT_MODEL_FALLBACKS."""
     import timmy.agent as agent_mod