Harden M8 preflight foundation

tests/test_tool.py

@@ -581,6 +581,46 @@ class TestDefaultCategories:
         assert "Other" in DEFAULT_CATEGORIES
 
 
+class TestToolContracts:
+    def test_config_must_be_mapping(self):
+        with pytest.raises(ValueError, match="YAML mapping"):
+            Tool.from_dict(["not", "a", "mapping"])
+
+    def test_legacy_source_string_is_normalized(self):
+        tool = Tool.from_dict({"name": "legacy-source", "source": "old/tool"})
+        assert tool.source is not None
+        assert tool.source.type == "imported"
+        assert tool.source.original_tool == "old/tool"
+
+    def test_contracts_roundtrip(self):
+        tool = Tool(
+            name="contract-tool",
+            input_schema={"type": "string"},
+            output_schema={"type": "array", "items": {"type": "integer"}},
+        )
+        restored = Tool.from_dict(tool.to_dict())
+        assert restored.input_schema == {"type": "string"}
+        assert restored.output_schema["type"] == "array"
+
+    def test_empty_contracts_are_preserved(self):
+        tool = Tool(name="open-contract", input_schema={}, output_schema={})
+        serialized = tool.to_dict()
+        assert serialized["input_schema"] == {}
+        assert serialized["output_schema"] == {}
+
+    @pytest.mark.parametrize(
+        ("field", "schema"),
+        [
+            ("input_schema", "string"),
+            ("output_schema", {"type": "not-a-json-schema-type"}),
+            ("output_schema", {"required": "name"}),
+        ],
+    )
+    def test_invalid_contract_is_rejected(self, field, schema):
+        with pytest.raises(ValueError, match=field):
+            Tool(name="bad-contract", **{field: schema})
+
+
 class TestAgentContext:
     def test_toolstep_profile_roundtrip(self):
         step = ToolStep(tool="my-tool", output_var="out", profile="architect")