test(workspace): add 39-case coverage for shared_runtime helper functions

Add comprehensive tests for the 6 remaining untested helpers in
shared_runtime.py:
- _extract_part_text: 10 cases covering dict, object, root nesting
- extract_message_text: 6 cases for parts extraction and context objects
- format_conversation_history: 4 cases for role formatting
- build_task_text: 4 cases for history prepending
- append_peer_guidance: 5 cases for peer info injection
- brief_task: 6 cases for truncation

Net new: 39 tests for previously zero-covered helpers.

🤖 Generated with Claude Code

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

workspace/tests/test_shared_runtime_helpers.py

@@ -0,0 +1,266 @@
+"""Tests for shared_runtime helper functions.
+
+Covers the untested helpers in shared_runtime.py:
+- _extract_part_text
+- extract_message_text
+- format_conversation_history
+- build_task_text
+- append_peer_guidance
+- brief_task
+
+Does NOT cover set_current_task (async, covered in test_a2a_executor.py).
+"""
+
+from __future__ import annotations
+
+import sys
+
+# Ensure the workspace root is on the path so 'shared_runtime' resolves
+_ws_root = __file__.rsplit("/tests/", 1)[0]
+if _ws_root not in sys.path:
+    sys.path.insert(0, _ws_root)
+
+from shared_runtime import (
+    _extract_part_text,
+    extract_message_text,
+    format_conversation_history,
+    build_task_text,
+    append_peer_guidance,
+    brief_task,
+)
+
+
+# ─── _extract_part_text ──────────────────────────────────────────────────────
+
+class TestExtractPartText:
+    def test_dict_with_text(self):
+        assert _extract_part_text({"text": "hello world"}) == "hello world"
+
+    def test_dict_with_nested_root_text(self):
+        assert _extract_part_text({"root": {"text": "nested text"}}) == "nested text"
+
+    def test_dict_prefers_text_over_root(self):
+        # When both text and root exist, text wins (outer text)
+        assert _extract_part_text({"text": "outer", "root": {"text": "inner"}}) == "outer"
+
+    def test_dict_empty_text_and_root(self):
+        assert _extract_part_text({"kind": "text"}) == ""
+
+    def test_dict_missing_fields(self):
+        assert _extract_part_text({"kind": "image"}) == ""
+
+    def test_dict_mixed_with_extra_fields(self):
+        assert _extract_part_text({"kind": "text", "text": "foo", "url": "http://..."}) == "foo"
+
+    def test_object_with_text_attribute(self):
+        class PartObj:
+            text = "object text"
+
+        assert _extract_part_text(PartObj()) == "object text"
+
+    def test_object_with_root_text_attribute(self):
+        class RootObj:
+            text = "root object text"
+
+        class PartObj:
+            root = RootObj()
+
+        assert _extract_part_text(PartObj()) == "root object text"
+
+    def test_object_empty_text(self):
+        class EmptyObj:
+            text = ""
+
+        assert _extract_part_text(EmptyObj()) == ""
+
+    def test_object_no_text_or_root(self):
+        class NoTextObj:
+            pass
+
+        assert _extract_part_text(NoTextObj()) == ""
+
+    def test_none_like(self):
+        assert _extract_part_text(None) == ""
+
+
+# ─── extract_message_text ────────────────────────────────────────────────────
+
+class TestExtractMessageText:
+    def test_list_of_dict_parts(self):
+        parts = [{"text": "hello"}, {"text": "world"}]
+        assert extract_message_text(parts) == "hello world"
+
+    def test_single_part(self):
+        parts = [{"text": "only one"}]
+        assert extract_message_text(parts) == "only one"
+
+    def test_empty_list(self):
+        assert extract_message_text([]) == ""
+
+    def test_none_parts(self):
+        assert extract_message_text(None) == ""
+
+    def test_object_with_message_parts(self):
+        """Object with .message.parts attribute (A2A RequestContext pattern)."""
+        msg = type("Message", (), {"parts": [{"text": "from context"}, {"text": "message"}]})()
+        ctx = type("Context", (), {"message": msg})()
+        assert extract_message_text(ctx) == "from context message"
+
+    def test_joins_with_single_space(self):
+        # Inter-part join uses single space; internal whitespace within parts is preserved
+        parts = [{"text": "hello"}, {"text": "world"}]
+        assert extract_message_text(parts) == "hello world"
+
+    def test_preserves_within_part_whitespace(self):
+        parts = [{"text": "  spaced  "}, {"text": "\ttext\t"}]
+        # Leading/trailing whitespace stripped; internal whitespace within parts preserved
+        assert extract_message_text(parts) == "spaced   \ttext"
+
+    def test_skips_parts_without_text(self):
+        parts = [{"kind": "image"}, {"text": "visible"}, {"url": "http://x"}]
+        assert extract_message_text(parts) == "visible"
+
+
+# ─── format_conversation_history ──────────────────────────────────────────────
+
+class TestFormatConversationHistory:
+    def test_empty_history(self):
+        assert format_conversation_history([]) == ""
+
+    def test_single_user_message(self):
+        result = format_conversation_history([("human", "hello")])
+        assert "User: hello" in result
+
+    def test_single_agent_message(self):
+        result = format_conversation_history([("ai", "hi there")])
+        assert "Agent: hi there" in result
+
+    def test_interleaved_history(self):
+        history = [
+            ("human", "first"),
+            ("ai", "response one"),
+            ("human", "second"),
+            ("ai", "response two"),
+        ]
+        result = format_conversation_history(history)
+        lines = result.strip().split("\n")
+        assert len(lines) == 4
+        assert lines[0] == "User: first"
+        assert lines[1] == "Agent: response one"
+        assert lines[2] == "User: second"
+        assert lines[3] == "Agent: response two"
+
+
+# ─── build_task_text ──────────────────────────────────────────────────────────
+
+class TestBuildTaskText:
+    def test_no_history_returns_user_message(self):
+        assert build_task_text("hello", []) == "hello"
+
+    def test_history_prepends_transcript(self):
+        history = [("human", "hi"), ("ai", "hello")]
+        result = build_task_text("send email", history)
+        assert "Conversation so far:" in result
+        assert "User: hi" in result
+        assert "Agent: hello" in result
+        assert "Current request: send email" in result
+
+    def test_empty_history_returns_user_message(self):
+        # Empty list should behave like no history
+        assert build_task_text("hello", []) == "hello"
+
+    def test_single_history_entry(self):
+        result = build_task_text("bye", [("human", "last")])
+        assert "User: last" in result
+        assert "Current request: bye" in result
+
+
+# ─── append_peer_guidance ─────────────────────────────────────────────────────
+
+class TestAppendPeerGuidance:
+    def test_no_base_text_uses_default(self):
+        result = append_peer_guidance(
+            None,
+            "peer info here",
+            default_text="default",
+            tool_name="delegate_task",
+        )
+        assert "peer info here" in result
+        assert "## Peers" in result
+        assert "delegate_task" in result
+        assert "default" in result
+
+    def test_base_text_preserved(self):
+        result = append_peer_guidance(
+            "my prompt",
+            "peer info",
+            default_text="fallback",
+            tool_name="delegate_task",
+        )
+        assert "my prompt" in result
+        assert "## Peers" in result
+
+    def test_empty_peers_info_skipped(self):
+        result = append_peer_guidance(
+            "my prompt",
+            "",
+            default_text="fallback",
+            tool_name="delegate_task",
+        )
+        assert result == "my prompt"
+
+    def test_whitespace_trimmed(self):
+        result = append_peer_guidance(
+            "  prompt  ",
+            " peers ",
+            default_text="fallback",
+            tool_name="delegate_task",
+        )
+        # Should not double-space
+        assert "  " not in result
+
+    def test_tool_name_injected(self):
+        result = append_peer_guidance(
+            None,
+            "peer info",
+            default_text="default",
+            tool_name="my_tool",
+        )
+        assert "my_tool" in result
+
+
+# ─── brief_task ───────────────────────────────────────────────────────────────
+
+class TestBriefTask:
+    def test_short_text_unchanged(self):
+        assert brief_task("hello world") == "hello world"
+
+    def test_exactly_at_limit(self):
+        text = "a" * 60
+        assert brief_task(text) == text
+
+    def test_over_limit_truncates(self):
+        text = "a" * 100
+        result = brief_task(text)
+        assert len(result) == 63  # 60 + "..."
+        assert result.endswith("...")
+
+    def test_under_limit_no_ellipsis(self):
+        text = "a" * 59
+        result = brief_task(text)
+        assert result == text
+        assert "..." not in result
+
+    def test_default_limit_60(self):
+        text = "a" * 70
+        result = brief_task(text, limit=60)
+        assert len(result) == 63
+
+    def test_custom_limit(self):
+        text = "a" * 20
+        result = brief_task(text, limit=10)
+        assert len(result) == 13  # 10 + "..."
+
+    def test_empty_string(self):
+        assert brief_task("") == ""
+        assert brief_task("") == ""  # no ellipsis for empty