diff --git a/tests/test_ext/test_ext_modified.py b/tests/test_ext/test_ext_modified.py
new file mode 100644
index 00000000..c1d0e3c2
--- /dev/null
+++ b/tests/test_ext/test_ext_modified.py
@@ -0,0 +1,132 @@
+"""
+novelWriter – Wheel Event Filter Tester
+=======================================
+
+This file is a part of novelWriter
+Copyright 2018–2024, Veronica Berglyd Olsen
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <https://www.gnu.org/licenses/>.
+"""
+from __future__ import annotations
+
+import pytest
+
+from tools import SimpleDialog
+
+from PyQt5.QtGui import QWheelEvent
+from PyQt5.QtCore import QPoint, QPointF, Qt
+
+from novelwriter.extensions.modified import NComboBox, NDoubleSpinBox, NSpinBox
+
+
+class MockWheelEvent(QWheelEvent):
+
+    def __init__(self):
+        super().__init__(
+            QPointF(0, 0), QPointF(0, 0), QPoint(0, 0), QPoint(0, 0),
+            Qt.MouseButton.NoButton, Qt.KeyboardModifier.NoModifier,
+            Qt.ScrollPhase.ScrollUpdate, False
+        )
+        self.ignored = False
+        return
+
+    def ignore(self):
+        super().ignore()
+        self.ignored = True
+        return
+
+# END Class MockWheelEvent
+
+
+@pytest.mark.gui
+def testExtModified_NComboBox(qtbot, monkeypatch):
+    """Test the NComboBox class."""
+    widget = NComboBox()
+    widget.addItem("Item 1", 1)
+    widget.addItem("Item 2", 2)
+
+    dialog = SimpleDialog(widget)
+    dialog.show()
+
+    with monkeypatch.context() as mp:
+        mp.setattr(NComboBox, "hasFocus", lambda *a: True)
+        event = MockWheelEvent()
+        widget.wheelEvent(event)
+        assert event.ignored is False
+
+    with monkeypatch.context() as mp:
+        mp.setattr(NComboBox, "hasFocus", lambda *a: False)
+        event = MockWheelEvent()
+        widget.wheelEvent(event)
+        assert event.ignored is True
+
+    # qtbot.stop()
+
+# END Test testExtModified_NComboBox
+
+
+@pytest.mark.gui
+def testExtModified_NSpinBox(qtbot, monkeypatch):
+    """Test the NSpinBox class."""
+    widget = NSpinBox()
+    widget.setMinimum(0)
+    widget.setMaximum(100)
+    widget.setValue(42)
+
+    dialog = SimpleDialog(widget)
+    dialog.show()
+
+    with monkeypatch.context() as mp:
+        mp.setattr(NSpinBox, "hasFocus", lambda *a: True)
+        event = MockWheelEvent()
+        widget.wheelEvent(event)
+        assert event.ignored is False
+
+    with monkeypatch.context() as mp:
+        mp.setattr(NSpinBox, "hasFocus", lambda *a: False)
+        event = MockWheelEvent()
+        widget.wheelEvent(event)
+        assert event.ignored is True
+
+    # qtbot.stop()
+
+# END Test testExtModified_NSpinBox
+
+
+@pytest.mark.gui
+def testExtModified_NDoubleSpinBox(qtbot, monkeypatch):
+    """Test the NDoubleSpinBox class."""
+    widget = NDoubleSpinBox()
+    widget.setMinimum(0.0)
+    widget.setMaximum(100.0)
+    widget.setValue(42.0)
+
+    dialog = SimpleDialog(widget)
+    dialog.show()
+
+    with monkeypatch.context() as mp:
+        mp.setattr(NDoubleSpinBox, "hasFocus", lambda *a: True)
+        event = MockWheelEvent()
+        widget.wheelEvent(event)
+        assert event.ignored is False
+
+    with monkeypatch.context() as mp:
+        mp.setattr(NDoubleSpinBox, "hasFocus", lambda *a: False)
+        event = MockWheelEvent()
+        widget.wheelEvent(event)
+        assert event.ignored is True
+
+    # qtbot.stop()
+
+# END Test testExtModified_NDoubleSpinBox
diff --git a/tests/tools.py b/tests/tools.py
index 2da23818..7a00b4b6 100644
--- a/tests/tools.py
+++ b/tests/tools.py
@@ -25,7 +25,7 @@ import shutil
 from pathlib import Path
 from datetime import datetime
 
-from PyQt5.QtWidgets import qApp
+from PyQt5.QtWidgets import QDialog, QVBoxLayout, QWidget, qApp
 
 XML_IGNORE = ("<novelWriterXML", "<project")
 ODT_IGNORE = ("<meta:generator", "<meta:creation-date", "<dc:date", "<meta:editing")
@@ -214,3 +214,23 @@ def buildTestProject(obj: object, projPath: Path) -> None:
         nwGUI.rebuildTrees()
 
     return
+
+
+class SimpleDialog(QDialog):
+
+    def __init__(self, widget: QWidget) -> None:
+        super().__init__()
+        self._widget = widget
+
+        layout = QVBoxLayout()
+        layout.addWidget(widget)
+        layout.setContentsMargins(40, 40, 40, 40)
+        self.setLayout(layout)
+
+        return
+
+    @property
+    def widget(self) -> QWidget:
+        return self._widget
+
+# END Class TestDialog