Improve socket handling for -x spawned fenrir instances.

tests/unit/test_x11_terminal_mode.py

@@ -30,14 +30,17 @@ def test_x11_mode_runs_in_foreground():
 
 
 @pytest.mark.unit
-def test_x11_mode_rejects_other_emulated_modes():
+def test_removed_emulated_pty_flag_is_rejected():
     fenrir = load_fenrir_entrypoint()
-    args = fenrir.create_argument_parser().parse_args(["-x", "-e"])
+    with pytest.raises(SystemExit):
+        fenrir.create_argument_parser().parse_args(["-e"])
 
-    is_valid, error = fenrir.validate_arguments(args)
 
-    assert is_valid is False
-    assert "--x11" in error
+@pytest.mark.unit
+def test_removed_emulated_evdev_flag_is_rejected():
+    fenrir = load_fenrir_entrypoint()
+    with pytest.raises(SystemExit):
+        fenrir.create_argument_parser().parse_args(["-E"])
 
 
 @pytest.mark.unit
@@ -50,6 +53,19 @@ def test_x11_cli_accepts_window_id():
     assert args.x11_window_id == "0x123"
 
 
+@pytest.mark.unit
+def test_x11_window_id_requires_x11_mode():
+    fenrir = load_fenrir_entrypoint()
+    args = fenrir.create_argument_parser().parse_args(
+        ["--x11-window-id", "0x123"]
+    )
+
+    is_valid, error = fenrir.validate_arguments(args)
+
+    assert is_valid is False
+    assert "--x11-window-id requires --x11" == error
+
+
 @pytest.mark.unit
 def test_x11_key_name_mapping_for_keypad_and_capslock():
     x11 = X11Driver()