refactor(tests): reorganize tests into unittest/ and e2e/ directories

- Move all unit tests from tests/ to tests/unittest/
- Add tests/e2e/ directory for end-to-end tests
- Update conftest.py for new test structure
- Add new tests for auth dependencies, policies, route injection
- Add new tests for run callbacks, create store, execution artifacts
- Remove obsolete tests for deleted persistence layer

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/tests/unittest/test_reflection_resolvers.py

@@ -0,0 +1,49 @@
+"""Tests for reflection resolvers."""
+
+import pytest
+
+from deerflow.reflection import resolvers
+from deerflow.reflection.resolvers import resolve_variable
+
+
+def test_resolve_variable_reports_install_hint_for_missing_google_provider(monkeypatch: pytest.MonkeyPatch):
+    """Missing google provider should return actionable install guidance."""
+
+    def fake_import_module(module_path: str):
+        raise ModuleNotFoundError(f"No module named '{module_path}'", name=module_path)
+
+    monkeypatch.setattr(resolvers, "import_module", fake_import_module)
+
+    with pytest.raises(ImportError) as exc_info:
+        resolve_variable("langchain_google_genai:ChatGoogleGenerativeAI")
+
+    message = str(exc_info.value)
+    assert "Could not import module langchain_google_genai" in message
+    assert "uv add langchain-google-genai" in message
+
+
+def test_resolve_variable_reports_install_hint_for_missing_google_transitive_dependency(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """Missing transitive dependency should still return actionable install guidance."""
+
+    def fake_import_module(module_path: str):
+        # Simulate provider module existing but a transitive dependency (e.g. `google`) missing.
+        raise ModuleNotFoundError("No module named 'google'", name="google")
+
+    monkeypatch.setattr(resolvers, "import_module", fake_import_module)
+
+    with pytest.raises(ImportError) as exc_info:
+        resolve_variable("langchain_google_genai:ChatGoogleGenerativeAI")
+
+    message = str(exc_info.value)
+    # Even when a transitive dependency is missing, the hint should still point to the provider package.
+    assert "uv add langchain-google-genai" in message
+
+
+def test_resolve_variable_invalid_path_format():
+    """Invalid variable path should fail with format guidance."""
+    with pytest.raises(ImportError) as exc_info:
+        resolve_variable("invalid.variable.path")
+
+    assert "doesn't look like a variable path" in str(exc_info.value)