diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index ea2ed6e..496d18b 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -20,8 +20,13 @@ jobs:
       - name: Install dependencies
         run: pip install -r requirements-dev.txt
 
+      - name: Install Xvfb for the UI tests
+        run: sudo apt-get update && sudo apt-get install -y xvfb
+
       - name: Run tests
-        run: pytest
+        run: xvfb-run -a pytest
+        env:
+          REQUIRE_UI_TESTS: "1"
 
   lint:
     runs-on: ubuntu-latest
diff --git a/readme.md b/readme.md
index b7c1503..524c7ca 100644
--- a/readme.md
+++ b/readme.md
@@ -168,5 +168,6 @@ pip install -r requirements-dev.txt
 | Type checks | `mypy` |
 
 The UI tests are skipped when no display is available. On Linux they can be run with `xvfb-run -a pytest`.
+CI sets `REQUIRE_UI_TESTS=1`, which makes them fail instead of being skipped.
 
 Pull requests target the `dev` branch.
diff --git a/renovate.json b/renovate.json
index 1bc58cd..b6eb8bc 100644
--- a/renovate.json
+++ b/renovate.json
@@ -1,7 +1,7 @@
 {
   "$schema": "https://docs.renovatebot.com/renovate-schema.json",
   "extends": [
-    "config:base"
+    "config:recommended"
   ],
   "rebaseWhen": "conflicted",
   "labels": [
diff --git a/test/tkinter_floor_test.py b/test/tkinter_floor_test.py
index 5904b5e..d5c8dfb 100644
--- a/test/tkinter_floor_test.py
+++ b/test/tkinter_floor_test.py
@@ -1,6 +1,5 @@
 """Unit tests for the TkinterFloor class."""
 
-import importlib.util
 import unittest
 
 import numpy
@@ -8,11 +7,10 @@
 from floors.floor import Floor
 from generators.generator import Generator
 from rooms.teleport_room import TeleportRoom
+from ui_test_support import requires_tkinter
 
-_HAS_TKINTER = importlib.util.find_spec("tkinter") is not None
 
-
-@unittest.skipUnless(_HAS_TKINTER, "tkinter is not available")
+@requires_tkinter()
 class TkinterFloorTest(unittest.TestCase):
     def setUp(self) -> None:
         # pylint: disable=import-outside-toplevel
diff --git a/test/tkinter_generator_test.py b/test/tkinter_generator_test.py
index a584e0a..8478b1b 100644
--- a/test/tkinter_generator_test.py
+++ b/test/tkinter_generator_test.py
@@ -1,30 +1,15 @@
 """Unit tests for the TkinterGenerator class."""
 
-import importlib.util
 import tempfile
 import time
 import unittest
 from unittest import mock
 
+from ui_test_support import requires_display
 from utils import globals as my_globals
 
-_HAS_TKINTER = importlib.util.find_spec("tkinter") is not None
 
-
-def _has_display() -> bool:
-    if not _HAS_TKINTER:
-        return False
-    # pylint: disable=import-outside-toplevel
-    import tkinter
-
-    try:
-        tkinter.Tk().destroy()
-    except tkinter.TclError:
-        return False
-    return True
-
-
-@unittest.skipUnless(_has_display(), "tkinter or a display is not available")
+@requires_display()
 class TkinterGeneratorTest(unittest.TestCase):
     def setUp(self) -> None:
         # pylint: disable=import-outside-toplevel
diff --git a/test/tkinter_teleport_room_test.py b/test/tkinter_teleport_room_test.py
index aaff632..c753596 100644
--- a/test/tkinter_teleport_room_test.py
+++ b/test/tkinter_teleport_room_test.py
@@ -1,14 +1,12 @@
 """Unit tests for the TkinterTeleportRoom class."""
 
-import importlib.util
 import unittest
 
+from ui_test_support import requires_tkinter
 from utils.room_type import RoomType
 
-_HAS_TKINTER = importlib.util.find_spec("tkinter") is not None
 
-
-@unittest.skipUnless(_HAS_TKINTER, "tkinter is not available")
+@requires_tkinter()
 class TkinterTeleportRoomTest(unittest.TestCase):
     def setUp(self) -> None:
         # pylint: disable=import-outside-toplevel
diff --git a/test/ui_test_support.py b/test/ui_test_support.py
new file mode 100644
index 0000000..80b1dd4
--- /dev/null
+++ b/test/ui_test_support.py
@@ -0,0 +1,60 @@
+"""
+Helpers to skip the UI tests when tkinter or a display is not available.
+
+Set the environment variable REQUIRE_UI_TESTS=1 to make these tests fail
+instead of being skipped, e.g. in CI where they must always run.
+"""
+
+import importlib.util
+import os
+import unittest
+from typing import Callable, TypeVar
+
+T = TypeVar("T")
+
+_REQUIRED = os.environ.get("REQUIRE_UI_TESTS") == "1"
+
+
+def has_tkinter() -> bool:
+    """
+    Returns if tkinter can be imported.
+    """
+    return importlib.util.find_spec("tkinter") is not None
+
+
+def has_display() -> bool:
+    """
+    Returns if tkinter can open a window.
+    """
+    if not has_tkinter():
+        return False
+    # pylint: disable=import-outside-toplevel
+    import tkinter
+
+    try:
+        tkinter.Tk().destroy()
+    except tkinter.TclError:
+        return False
+    return True
+
+
+def _require(available: bool, reason: str) -> Callable[[T], T]:
+    if available:
+        return lambda test: test
+    if _REQUIRED:
+        raise RuntimeError(f"UI tests are required but {reason}")
+    return unittest.skip(reason)
+
+
+def requires_tkinter() -> Callable[[T], T]:
+    """
+    Skips the decorated tests if tkinter is not available.
+    """
+    return _require(has_tkinter(), "tkinter is not available")
+
+
+def requires_display() -> Callable[[T], T]:
+    """
+    Skips the decorated tests if tkinter cannot open a window.
+    """
+    return _require(has_display(), "tkinter or a display is not available")