Pin text I/O to UTF-8 and fail CI on locale-dependent reads/writes (#3296)

Co-authored-by: ShuQingDollarVoyager <57471784+ShuQingDollarVoyager@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

tests/server/mcpserver/resources/test_file_resources.py

@@ -16,7 +16,7 @@ def temp_file():
     File is automatically cleaned up after the test if it still exists.
     """
     content = "test content"
-    with NamedTemporaryFile(mode="w", delete=False) as f:
+    with NamedTemporaryFile(mode="w", encoding="utf-8", delete=False) as f:
         f.write(content)
         path = Path(f.name).resolve()
     yield path

tests/server/mcpserver/servers/test_file_server.py

@@ -13,9 +13,9 @@ def test_dir(tmp_path_factory: pytest.TempPathFactory) -> Path:
     tmp = tmp_path_factory.mktemp("test_files")
 
     # Create test files
-    (tmp / "example.py").write_text("print('hello world')")
-    (tmp / "readme.md").write_text("# Test Directory\nThis is a test.")
-    (tmp / "config.json").write_text('{"test": true}')
+    (tmp / "example.py").write_text("print('hello world')", encoding="utf-8")
+    (tmp / "readme.md").write_text("# Test Directory\nThis is a test.", encoding="utf-8")
+    (tmp / "config.json").write_text('{"test": true}', encoding="utf-8")
 
     return tmp
 
@@ -38,7 +38,7 @@ def resources(mcp: MCPServer, test_dir: Path) -> MCPServer:
     def read_example_py() -> str:
         """Read the example.py file"""
         try:
-            return (test_dir / "example.py").read_text()
+            return (test_dir / "example.py").read_text(encoding="utf-8")
         except FileNotFoundError:
             return "File not found"
 
@@ -46,7 +46,7 @@ def resources(mcp: MCPServer, test_dir: Path) -> MCPServer:
     def read_readme_md() -> str:
         """Read the readme.md file"""
         try:  # pragma: no cover
-            return (test_dir / "readme.md").read_text()
+            return (test_dir / "readme.md").read_text(encoding="utf-8")
         except FileNotFoundError:  # pragma: no cover
             return "File not found"
 
@@ -54,7 +54,7 @@ def resources(mcp: MCPServer, test_dir: Path) -> MCPServer:
     def read_config_json() -> str:
         """Read the config.json file"""
         try:  # pragma: no cover
-            return (test_dir / "config.json").read_text()
+            return (test_dir / "config.json").read_text(encoding="utf-8")
         except FileNotFoundError:  # pragma: no cover
             return "File not found"
 

tests/server/mcpserver/test_server.py

@@ -819,7 +819,7 @@ class TestServerResources:
 
         # Create a text file
         text_file = tmp_path / "test.txt"
-        text_file.write_text("Hello from file!")
+        text_file.write_text("Hello from file!", encoding="utf-8")
 
         resource = FileResource(uri="file://test.txt", name="test.txt", path=text_file)
         mcp.add_resource(resource)