refactor(tests): optimize unit test structure

tests/agent/test_loop_save_turn.py

@@ -0,0 +1,74 @@
+from nanobot.agent.context import ContextBuilder
+from nanobot.agent.loop import AgentLoop
+from nanobot.session.manager import Session
+
+
+def _mk_loop() -> AgentLoop:
+    loop = AgentLoop.__new__(AgentLoop)
+    loop._TOOL_RESULT_MAX_CHARS = AgentLoop._TOOL_RESULT_MAX_CHARS
+    return loop
+
+
+def test_save_turn_skips_multimodal_user_when_only_runtime_context() -> None:
+    loop = _mk_loop()
+    session = Session(key="test:runtime-only")
+    runtime = ContextBuilder._RUNTIME_CONTEXT_TAG + "\nCurrent Time: now (UTC)"
+
+    loop._save_turn(
+        session,
+        [{"role": "user", "content": [{"type": "text", "text": runtime}]}],
+        skip=0,
+    )
+    assert session.messages == []
+
+
+def test_save_turn_keeps_image_placeholder_with_path_after_runtime_strip() -> None:
+    loop = _mk_loop()
+    session = Session(key="test:image")
+    runtime = ContextBuilder._RUNTIME_CONTEXT_TAG + "\nCurrent Time: now (UTC)"
+
+    loop._save_turn(
+        session,
+        [{
+            "role": "user",
+            "content": [
+                {"type": "text", "text": runtime},
+                {"type": "image_url", "image_url": {"url": "data:image/png;base64,abc"}, "_meta": {"path": "/media/feishu/photo.jpg"}},
+            ],
+        }],
+        skip=0,
+    )
+    assert session.messages[0]["content"] == [{"type": "text", "text": "[image: /media/feishu/photo.jpg]"}]
+
+
+def test_save_turn_keeps_image_placeholder_without_meta() -> None:
+    loop = _mk_loop()
+    session = Session(key="test:image-no-meta")
+    runtime = ContextBuilder._RUNTIME_CONTEXT_TAG + "\nCurrent Time: now (UTC)"
+
+    loop._save_turn(
+        session,
+        [{
+            "role": "user",
+            "content": [
+                {"type": "text", "text": runtime},
+                {"type": "image_url", "image_url": {"url": "data:image/png;base64,abc"}},
+            ],
+        }],
+        skip=0,
+    )
+    assert session.messages[0]["content"] == [{"type": "text", "text": "[image]"}]
+
+
+def test_save_turn_keeps_tool_results_under_16k() -> None:
+    loop = _mk_loop()
+    session = Session(key="test:tool-result")
+    content = "x" * 12_000
+
+    loop._save_turn(
+        session,
+        [{"role": "tool", "tool_call_id": "call_1", "name": "read_file", "content": content}],
+        skip=0,
+    )
+
+    assert session.messages[0]["content"] == content