test: rewrite cli.claude config tests to assert JSON output directly (#2311)

Co-authored-by: claude[bot] <209825114+claude[bot]@users.noreply.github.com>
Co-authored-by: Felix Weinberger <felixweinberger@users.noreply.github.com>

src/mcp/cli/claude.py

@@ -33,7 +33,7 @@ def get_claude_config_path() -> Path | None:  # pragma: no cover
 def get_uv_path() -> str:
     """Get the full path to the uv executable."""
     uv_path = shutil.which("uv")
-    if not uv_path:  # pragma: no cover
+    if not uv_path:
         logger.error(
             "uv executable not found in PATH, falling back to 'uv'. Please ensure uv is installed and in your PATH"
         )
@@ -65,7 +65,7 @@ def update_claude_config(
     """
     config_dir = get_claude_config_path()
     uv_path = get_uv_path()
-    if not config_dir:  # pragma: no cover
+    if not config_dir:
         raise RuntimeError(
             "Claude Desktop config directory not found. Please ensure Claude Desktop"
             " is installed and has been run at least once to initialize its config."
@@ -90,7 +90,7 @@ def update_claude_config(
             config["mcpServers"] = {}
 
         # Always preserve existing env vars and merge with new ones
-        if server_name in config["mcpServers"] and "env" in config["mcpServers"][server_name]:  # pragma: no cover
+        if server_name in config["mcpServers"] and "env" in config["mcpServers"][server_name]:
             existing_env = config["mcpServers"][server_name]["env"]
             if env_vars:
                 # New vars take precedence over existing ones
@@ -103,22 +103,26 @@ def update_claude_config(
 
         # Collect all packages in a set to deduplicate
         packages = {MCP_PACKAGE}
-        if with_packages:  # pragma: no cover
+        if with_packages:
             packages.update(pkg for pkg in with_packages if pkg)
 
         # Add all packages with --with
         for pkg in sorted(packages):
             args.extend(["--with", pkg])
 
-        if with_editable:  # pragma: no cover
+        if with_editable:
             args.extend(["--with-editable", str(with_editable)])
 
         # Convert file path to absolute before adding to command
         # Split off any :object suffix first
-        if ":" in file_spec:
+        # First check if we have a Windows path (e.g., C:\...)
+        has_windows_drive = len(file_spec) > 1 and file_spec[1] == ":"
+
+        # Split on the last colon, but only if it's not part of the Windows drive letter
+        if ":" in (file_spec[2:] if has_windows_drive else file_spec):
             file_path, server_object = file_spec.rsplit(":", 1)
             file_spec = f"{Path(file_path).resolve()}:{server_object}"
-        else:  # pragma: no cover
+        else:
             file_spec = str(Path(file_spec).resolve())
 
         # Add mcp run command
@@ -127,7 +131,7 @@ def update_claude_config(
         server_config: dict[str, Any] = {"command": uv_path, "args": args}
 
         # Add environment variables if specified
-        if env_vars:  # pragma: no cover
+        if env_vars:
             server_config["env"] = env_vars
 
         config["mcpServers"][server_name] = server_config

tests/cli/test_claude.py

@@ -0,0 +1,146 @@
+"""Tests for mcp.cli.claude — Claude Desktop config file generation."""
+
+import json
+from pathlib import Path
+from typing import Any
+
+import pytest
+
+from mcp.cli.claude import get_uv_path, update_claude_config
+
+
+@pytest.fixture
+def config_dir(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> Path:
+    """Temp Claude config dir with get_claude_config_path and get_uv_path mocked."""
+    claude_dir = tmp_path / "Claude"
+    claude_dir.mkdir()
+    monkeypatch.setattr("mcp.cli.claude.get_claude_config_path", lambda: claude_dir)
+    monkeypatch.setattr("mcp.cli.claude.get_uv_path", lambda: "/fake/bin/uv")
+    return claude_dir
+
+
+def _read_server(config_dir: Path, name: str) -> dict[str, Any]:
+    config = json.loads((config_dir / "claude_desktop_config.json").read_text())
+    return config["mcpServers"][name]
+
+
+def test_generates_uv_run_command(config_dir: Path):
+    """Should write a uv run command that invokes mcp run on the resolved file spec."""
+    assert update_claude_config(file_spec="server.py:app", server_name="my_server")
+
+    resolved = Path("server.py").resolve()
+    assert _read_server(config_dir, "my_server") == {
+        "command": "/fake/bin/uv",
+        "args": ["run", "--frozen", "--with", "mcp[cli]", "mcp", "run", f"{resolved}:app"],
+    }
+
+
+def test_file_spec_without_object_suffix(config_dir: Path):
+    """File specs without :object should still resolve to an absolute path."""
+    assert update_claude_config(file_spec="server.py", server_name="s")
+
+    assert _read_server(config_dir, "s")["args"][-1] == str(Path("server.py").resolve())
+
+
+def test_with_packages_sorted_and_deduplicated(config_dir: Path):
+    """Extra packages should appear as --with flags, sorted and deduplicated with mcp[cli]."""
+    assert update_claude_config(file_spec="s.py:app", server_name="s", with_packages=["zebra", "aardvark", "zebra"])
+
+    args = _read_server(config_dir, "s")["args"]
+    assert args[:8] == ["run", "--frozen", "--with", "aardvark", "--with", "mcp[cli]", "--with", "zebra"]
+
+
+def test_with_editable_adds_flag(config_dir: Path, tmp_path: Path):
+    """with_editable should add --with-editable after the --with flags."""
+    editable = tmp_path / "project"
+    assert update_claude_config(file_spec="s.py:app", server_name="s", with_editable=editable)
+
+    args = _read_server(config_dir, "s")["args"]
+    assert args[4:6] == ["--with-editable", str(editable)]
+
+
+def test_env_vars_written(config_dir: Path):
+    """env_vars should be written under the server's env key."""
+    assert update_claude_config(file_spec="s.py:app", server_name="s", env_vars={"KEY": "val"})
+
+    assert _read_server(config_dir, "s")["env"] == {"KEY": "val"}
+
+
+def test_existing_env_vars_merged_new_wins(config_dir: Path):
+    """Re-installing should merge env vars, with new values overriding existing ones."""
+    (config_dir / "claude_desktop_config.json").write_text(
+        json.dumps({"mcpServers": {"s": {"env": {"OLD": "keep", "KEY": "old"}}}})
+    )
+
+    assert update_claude_config(file_spec="s.py:app", server_name="s", env_vars={"KEY": "new"})
+
+    assert _read_server(config_dir, "s")["env"] == {"OLD": "keep", "KEY": "new"}
+
+
+def test_existing_env_vars_preserved_without_new(config_dir: Path):
+    """Re-installing without env_vars should keep the existing env block intact."""
+    (config_dir / "claude_desktop_config.json").write_text(json.dumps({"mcpServers": {"s": {"env": {"KEEP": "me"}}}}))
+
+    assert update_claude_config(file_spec="s.py:app", server_name="s")
+
+    assert _read_server(config_dir, "s")["env"] == {"KEEP": "me"}
+
+
+def test_other_servers_preserved(config_dir: Path):
+    """Installing a new server should not clobber existing mcpServers entries."""
+    (config_dir / "claude_desktop_config.json").write_text(json.dumps({"mcpServers": {"other": {"command": "x"}}}))
+
+    assert update_claude_config(file_spec="s.py:app", server_name="s")
+
+    config = json.loads((config_dir / "claude_desktop_config.json").read_text())
+    assert set(config["mcpServers"]) == {"other", "s"}
+    assert config["mcpServers"]["other"] == {"command": "x"}
+
+
+def test_raises_when_config_dir_missing(monkeypatch: pytest.MonkeyPatch):
+    """Should raise RuntimeError when Claude Desktop config dir can't be found."""
+    monkeypatch.setattr("mcp.cli.claude.get_claude_config_path", lambda: None)
+    monkeypatch.setattr("mcp.cli.claude.get_uv_path", lambda: "/fake/bin/uv")
+
+    with pytest.raises(RuntimeError, match="Claude Desktop config directory not found"):
+        update_claude_config(file_spec="s.py:app", server_name="s")
+
+
+@pytest.mark.parametrize("which_result, expected", [("/usr/local/bin/uv", "/usr/local/bin/uv"), (None, "uv")])
+def test_get_uv_path(monkeypatch: pytest.MonkeyPatch, which_result: str | None, expected: str):
+    """Should return shutil.which's result, or fall back to bare 'uv' when not on PATH."""
+
+    def fake_which(cmd: str) -> str | None:
+        return which_result
+
+    monkeypatch.setattr("shutil.which", fake_which)
+    assert get_uv_path() == expected
+
+
+@pytest.mark.parametrize(
+    "file_spec, expected_last_arg",
+    [
+        ("C:\\Users\\server.py", "C:\\Users\\server.py"),
+        ("C:\\Users\\server.py:app", "C:\\Users\\server.py:app"),
+    ],
+)
+def test_windows_drive_letter_not_split(
+    config_dir: Path, monkeypatch: pytest.MonkeyPatch, file_spec: str, expected_last_arg: str
+):
+    """Drive-letter paths like 'C:\\server.py' must not be split on the drive colon.
+
+    Before the fix, a bare 'C:\\path\\server.py' would hit rsplit(":", 1) and yield
+    ("C", "\\path\\server.py"), calling resolve() on Path("C") instead of the full path.
+    """
+    seen: list[str] = []
+
+    def fake_resolve(self: Path) -> Path:
+        seen.append(str(self))
+        return self
+
+    monkeypatch.setattr(Path, "resolve", fake_resolve)
+
+    assert update_claude_config(file_spec=file_spec, server_name="s")
+
+    assert seen == ["C:\\Users\\server.py"]
+    assert _read_server(config_dir, "s")["args"][-1] == expected_last_arg

tests/client/test_config.py

@@ -1,75 +0,0 @@
-import json
-import subprocess
-from pathlib import Path
-from unittest.mock import patch
-
-import pytest
-
-from mcp.cli.claude import update_claude_config
-
-
-@pytest.fixture
-def temp_config_dir(tmp_path: Path):
-    """Create a temporary Claude config directory."""
-    config_dir = tmp_path / "Claude"
-    config_dir.mkdir()
-    return config_dir
-
-
-@pytest.fixture
-def mock_config_path(temp_config_dir: Path):
-    """Mock get_claude_config_path to return our temporary directory."""
-    with patch("mcp.cli.claude.get_claude_config_path", return_value=temp_config_dir):
-        yield temp_config_dir
-
-
-def test_command_execution(mock_config_path: Path):
-    """Test that the generated command can actually be executed."""
-    # Setup
-    server_name = "test_server"
-    file_spec = "test_server.py:app"
-
-    # Update config
-    success = update_claude_config(file_spec=file_spec, server_name=server_name)
-    assert success
-
-    # Read the generated config
-    config_file = mock_config_path / "claude_desktop_config.json"
-    config = json.loads(config_file.read_text())
-
-    # Get the command and args
-    server_config = config["mcpServers"][server_name]
-    command = server_config["command"]
-    args = server_config["args"]
-
-    test_args = [command] + args + ["--help"]
-
-    result = subprocess.run(test_args, capture_output=True, text=True, timeout=20, check=False)
-
-    assert result.returncode == 0
-    assert "usage" in result.stdout.lower()
-
-
-def test_absolute_uv_path(mock_config_path: Path):
-    """Test that the absolute path to uv is used when available."""
-    # Mock the shutil.which function to return a fake path
-    mock_uv_path = "/usr/local/bin/uv"
-
-    with patch("mcp.cli.claude.get_uv_path", return_value=mock_uv_path):
-        # Setup
-        server_name = "test_server"
-        file_spec = "test_server.py:app"
-
-        # Update config
-        success = update_claude_config(file_spec=file_spec, server_name=server_name)
-        assert success
-
-        # Read the generated config
-        config_file = mock_config_path / "claude_desktop_config.json"
-        config = json.loads(config_file.read_text())
-
-        # Verify the command is the absolute path
-        server_config = config["mcpServers"][server_name]
-        command = server_config["command"]
-
-        assert command == mock_uv_path