diff --git a/astrodendro/tests/test_viewer.py b/astrodendro/tests/test_viewer.py
new file mode 100644
index 0000000..b6ad4b7
--- /dev/null
+++ b/astrodendro/tests/test_viewer.py
@@ -0,0 +1,40 @@
+import pytest
+import numpy as np
+
+import matplotlib.pyplot as plt
+from ..dendrogram import Dendrogram
+from matplotlib.backend_bases import MouseEvent
+
+
+DATA = np.array([[1, 3, 4, 4, 1, 4],
+                 [1, 2, 3, 2, 1, 3],
+                 [2, 1, 1, 3, 1, 2],
+                 [1, 1, 1, 1, 1, 1],
+                 [2, 3, 2, 1, 1, 2],
+                 [2, 3, 5, 3, 1, 1]])
+
+def test_viewer(capsys):
+
+    original_backend = plt.get_backend()
+
+    try:
+        plt.switch_backend('qtagg')
+    except ImportError:
+        pytest.skip("This test requires Qt to be installed")
+
+    d = Dendrogram.compute(DATA)
+    viewer = d.viewer()
+
+    plt.show(block=False)
+
+    cb = viewer.fig.canvas.callbacks
+
+    cb.process('button_press_event', MouseEvent('button_press_event', viewer.fig.canvas, 660, 520, 1))
+    cb.process('button_press_event', MouseEvent('button_press_event', viewer.fig.canvas, 890, 800, 1))
+    cb.process('button_press_event', MouseEvent('button_press_event', viewer.fig.canvas, 700, 700, 1))
+
+    plt.switch_backend(original_backend)
+
+    captured = capsys.readouterr()
+    assert captured.out == ""
+    assert captured.err == ""
diff --git a/tox.ini b/tox.ini
index c344359..a8b89f7 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,6 @@
 [tox]
 envlist =
-    py{38,39,310,311}-test{,-alldeps,-devdeps}{,-cov}
+    py{38,39,310,311}-test{,-alldeps,-devdeps,-viewer}{,-cov}
     build_docs
     linkcheck
     codestyle
@@ -10,6 +10,8 @@ requires =
 isolated_build = true
 
 [testenv]
+passenv =
+    DISPLAY
 setenv =
     MPLBACKEND=agg
     devdeps: PIP_EXTRA_INDEX_URL = https://pypi.anaconda.org/astropy/simple https://pypi.anaconda.org/scientific-python-nightly-wheels/
@@ -30,6 +32,7 @@ deps =
     oldestdeps: matplotlib==3.3.*
     oldestdeps: numpy==1.20.*
     oldestdeps: pillow==8.0.*
+    viewer: PyQt6
 
 extras =
     test