diff --git a/src/napari_matplotlib/tests/test_ui.py b/src/napari_matplotlib/tests/test_ui.py
new file mode 100644
index 00000000..3b30ad3a
--- /dev/null
+++ b/src/napari_matplotlib/tests/test_ui.py
@@ -0,0 +1,49 @@
+import pytest
+from qtpy.QtCore import QSize
+from qtpy.QtGui import QImage
+
+from napari_matplotlib import HistogramWidget, ScatterWidget, SliceWidget
+
+
+def _are_different(a: QImage, b: QImage) -> bool:
+    """
+    Check that a and b are identical, pixel by pixel. Via a stupid nested for loop.
+    """
+    assert not a.isNull()
+    assert not b.isNull()
+    assert a.size() == b.size()
+    for x in range(a.width()):
+        for y in range(a.height()):
+            if a.pixel(x, y) != b.pixel(x, y):
+                return True  # exit quickly
+    return False
+
+
+@pytest.mark.parametrize(
+    "Widget", [HistogramWidget, ScatterWidget, SliceWidget]
+)
+def test_mpl_toolbar_buttons_checked(make_napari_viewer, Widget):
+    """Test that the icons for checkable actions change when when a tool is selected.
+
+    A simple test of NapariNavigationToolbar._update_buttons_checked. Make sure the
+    checked and unchecked icons are not the same.
+    """
+    checkable_actions = ["Zoom", "Pan"]
+
+    viewer = make_napari_viewer()
+    widget = Widget(viewer)
+
+    # search through all of the icons for the ones whose icons are expected to
+    # change when checked
+    for action in widget.toolbar.actions():
+        if action.text() in checkable_actions:
+            assert action.isChecked() is False
+            assert action.isCheckable() is True
+            unchecked = action.icon().pixmap(QSize(48, 48)).toImage()
+
+            # simulate the user click (QTest.mouseClick can't take a QAction)
+            action.trigger()
+
+            assert action.isChecked() is True
+            checked = action.icon().pixmap(QSize(48, 48)).toImage()
+            assert _are_different(unchecked, checked)