fix: deep focus mode — single-problem context for Timmy (#409)

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

tests/timmy/test_focus.py

@@ -0,0 +1,113 @@
+"""Tests for timmy.focus — deep focus mode state management."""
+
+import json
+
+import pytest
+
+
+@pytest.fixture
+def focus_mgr(tmp_path):
+    """Create a FocusManager with a temporary state directory."""
+    from timmy.focus import FocusManager
+
+    return FocusManager(state_dir=tmp_path)
+
+
+class TestFocusManager:
+    """Unit tests for FocusManager."""
+
+    def test_default_state_is_broad(self, focus_mgr):
+        assert focus_mgr.get_mode() == "broad"
+        assert focus_mgr.get_topic() is None
+        assert not focus_mgr.is_focused()
+
+    def test_set_topic_activates_deep_focus(self, focus_mgr):
+        focus_mgr.set_topic("three-phase loop")
+        assert focus_mgr.get_topic() == "three-phase loop"
+        assert focus_mgr.get_mode() == "deep"
+        assert focus_mgr.is_focused()
+
+    def test_clear_returns_to_broad(self, focus_mgr):
+        focus_mgr.set_topic("bitcoin strategy")
+        focus_mgr.clear()
+        assert focus_mgr.get_topic() is None
+        assert focus_mgr.get_mode() == "broad"
+        assert not focus_mgr.is_focused()
+
+    def test_topic_strips_whitespace(self, focus_mgr):
+        focus_mgr.set_topic("  padded topic  ")
+        assert focus_mgr.get_topic() == "padded topic"
+
+    def test_focus_context_when_focused(self, focus_mgr):
+        focus_mgr.set_topic("memory architecture")
+        ctx = focus_mgr.get_focus_context()
+        assert "DEEP FOCUS MODE" in ctx
+        assert "memory architecture" in ctx
+
+    def test_focus_context_when_broad(self, focus_mgr):
+        assert focus_mgr.get_focus_context() == ""
+
+    def test_persistence_across_instances(self, tmp_path):
+        from timmy.focus import FocusManager
+
+        mgr1 = FocusManager(state_dir=tmp_path)
+        mgr1.set_topic("persistent problem")
+
+        # New instance should load persisted state
+        mgr2 = FocusManager(state_dir=tmp_path)
+        assert mgr2.get_topic() == "persistent problem"
+        assert mgr2.is_focused()
+
+    def test_clear_persists(self, tmp_path):
+        from timmy.focus import FocusManager
+
+        mgr1 = FocusManager(state_dir=tmp_path)
+        mgr1.set_topic("will be cleared")
+        mgr1.clear()
+
+        mgr2 = FocusManager(state_dir=tmp_path)
+        assert not mgr2.is_focused()
+        assert mgr2.get_topic() is None
+
+    def test_state_file_is_valid_json(self, tmp_path, focus_mgr):
+        focus_mgr.set_topic("json check")
+        state_file = tmp_path / "focus.json"
+        assert state_file.exists()
+        data = json.loads(state_file.read_text())
+        assert data["topic"] == "json check"
+        assert data["mode"] == "deep"
+
+    def test_missing_state_file_is_fine(self, tmp_path):
+        """FocusManager gracefully handles missing state file."""
+        from timmy.focus import FocusManager
+
+        mgr = FocusManager(state_dir=tmp_path / "nonexistent")
+        assert not mgr.is_focused()
+
+
+class TestPrependFocusContext:
+    """Tests for the session-level focus injection helper."""
+
+    def test_no_injection_when_unfocused(self, tmp_path, monkeypatch):
+        from timmy.focus import FocusManager
+
+        mgr = FocusManager(state_dir=tmp_path)
+        monkeypatch.setattr("timmy.focus.focus_manager", mgr)
+
+        from timmy.session import _prepend_focus_context
+
+        assert _prepend_focus_context("hello") == "hello"
+
+    def test_injection_when_focused(self, tmp_path, monkeypatch):
+        from timmy.focus import FocusManager
+
+        mgr = FocusManager(state_dir=tmp_path)
+        mgr.set_topic("test topic")
+        monkeypatch.setattr("timmy.focus.focus_manager", mgr)
+
+        from timmy.session import _prepend_focus_context
+
+        result = _prepend_focus_context("hello")
+        assert "DEEP FOCUS MODE" in result
+        assert "test topic" in result
+        assert result.endswith("hello")