test(s41): load-bearing preflight suite (AST no-network/no-auto-login guard + refusal teeth)

tests/test_preflight_loadbearing.py

@@ -0,0 +1,95 @@
+"""S4.1 preflight — load-bearing detach seams. Each test goes RED when the guarded mechanism is
+removed; a bare happy-path pass would not catch a regression here.
+"""
+
+from __future__ import annotations
+
+import ast
+import json
+from pathlib import Path
+
+import pytest
+
+from portfolio_optimiser.backends import Profile, resolve_model
+
+_PREFLIGHT = Path(__file__).resolve().parents[1] / "src" / "portfolio_optimiser" / "preflight.py"
+
+# Symbols preflight must never IMPORT (offline) or CALL (no auto-login). AST-based, NOT substring:
+# the `https` scheme literal contains `http`, and the module prose may mention the recipe — a
+# substring scan would false-positive (test_okf.py:216 lesson).
+_FORBIDDEN_IMPORTS = {
+    "socket",
+    "urllib",
+    "http",
+    "requests",
+    "httpx",
+    "ftplib",
+    "smtplib",
+    "subprocess",
+}
+_FORBIDDEN_CALLS = {"get_token", "DefaultAzureCredential", "AzureCliCredential"}
+
+
+def _preflight_ast() -> ast.Module:
+    return ast.parse(_PREFLIGHT.read_text(encoding="utf-8"))
+
+
+def test_sc6_no_network_or_autologin_in_preflight() -> None:
+    """SC6: preflight.py imports NO network/subprocess library and CALLS no credential-acquisition
+    symbol — so it can neither egress nor auto-log-in. Detach points: add a ``urllib``/``socket``
+    import, or a ``subprocess.run([...,"az","login"])`` / ``AzureCliCredential()`` call → RED. AST,
+    not substring: the ``https`` literal contains ``http`` and the docs recipe mentions ``az login``.
+
+    Scope honesty: this proves preflight.py's OWN direct imports are egress-free. ``preflight``
+    imports ``backends`` (which imports network-capable ``FoundryChatClient``), so "cannot egress"
+    holds precisely because preflight never CALLS client construction — not because the transitive
+    closure is import-free. The ``subprocess`` import ban makes shelling out to ``az login``
+    impossible (so the brief's literal "az login" symbol is covered transitively — a bare string
+    can't invoke anything without an import)."""
+    imported: list[str] = []
+    called: list[str] = []
+    for node in ast.walk(_preflight_ast()):
+        if isinstance(node, ast.Import):
+            imported += [a.name.split(".")[0] for a in node.names]
+        elif isinstance(node, ast.ImportFrom):
+            imported.append((node.module or "").split(".")[0])
+        elif isinstance(node, ast.Call):
+            fn = node.func
+            if isinstance(fn, ast.Name):
+                called.append(fn.id)
+            elif isinstance(fn, ast.Attribute):
+                called.append(fn.attr)
+    bad_imports = sorted(set(imported) & _FORBIDDEN_IMPORTS)
+    bad_calls = sorted(set(called) & _FORBIDDEN_CALLS)
+    assert bad_imports == [], f"preflight must have no network/subprocess import, found: {bad_imports}"
+    assert bad_calls == [], f"preflight must not acquire a credential/token, found: {bad_calls}"
+
+
+def test_sc1_refusal_names_the_exact_placeholder(monkeypatch: pytest.MonkeyPatch) -> None:
+    """SC1 teeth: the refusal names the EXACT bundled placeholder deployment (value-pinned). Detach
+    point: make the refusal generic (drop the offending id from the message) → RED."""
+    from portfolio_optimiser import preflight
+
+    monkeypatch.delenv("PORTFOLIO_MODEL_MAP", raising=False)
+    monkeypatch.setenv("PORTFOLIO_FOUNDRY_PROJECT_ENDPOINT", "https://x.services.ai.azure.com")
+    result = preflight.check_azure_preflight("azure")
+    assert isinstance(result, preflight.PreflightRefusal)
+    assert "REPLACE-WITH-FOUNDRY-DEPLOYMENT" in result.reason
+
+
+def test_sc4_resolve_model_guard_has_teeth(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    """SC4 teeth: resolve_model raises on a REPLACE-WITH-* azure deployment. Detach point: remove the
+    _PLACEHOLDER_PREFIX guard in resolve_model → it returns the placeholder → RED. Control: a valid
+    override returns the real id, so the raise fires only on the placeholder, not always."""
+    monkeypatch.delenv("PORTFOLIO_MODEL_MAP", raising=False)
+    with pytest.raises(ValueError, match="placeholder"):
+        resolve_model(Profile.AZURE, "proposer")
+    valid = tmp_path / "model_map.json"
+    valid.write_text(
+        json.dumps({"local": {"default": "qwen3:4b"}, "azure": {"default": "gpt-4o-mini"}}),
+        encoding="utf-8",
+    )
+    monkeypatch.setenv("PORTFOLIO_MODEL_MAP", str(valid))
+    assert resolve_model(Profile.AZURE, "proposer") == "gpt-4o-mini"