feat(gateway): 未知模型缺价发结构化告警——成本账缺项可观测（CR-M2-1）

packages/llm_gateway/tests/test_pricing.py

@@ -0,0 +1,29 @@
+"""pricing 单元测试（CR-M2-1：未知模型缺价应可观测）。"""
+
+from __future__ import annotations
+
+import structlog
+from ww_llm_gateway.pricing import cost_minor
+
+
+def test_known_model_computes_positive_cost() -> None:
+    # Arrange / Act
+    cost, currency = cost_minor("deepseek", "deepseek-chat", 1_000_000, 1_000_000)
+
+    # Assert
+    assert cost > 0
+    assert currency == "USD"
+
+
+def test_unknown_model_warns_and_still_returns_zero_cost() -> None:
+    # CR-M2-1：未知 (provider, model) 成本仍计 0（照常记账），但必须发结构化 warning
+    # 点名该 model——缺价条目应在成本账路径可见，而非静默吞成 0。
+    with structlog.testing.capture_logs() as logs:
+        cost, currency = cost_minor("mystery", "ghost-model", 1000, 2000)
+
+    assert cost == 0
+    assert currency == "USD"
+    warning = next(entry for entry in logs if entry["event"] == "pricing_unknown_model")
+    assert warning["log_level"] == "warning"
+    assert warning["provider"] == "mystery"
+    assert warning["model"] == "ghost-model"