diff --git a/ultraplot/demos.py b/ultraplot/demos.py
index 9b306420b..c535329fb 100644
--- a/ultraplot/demos.py
+++ b/ultraplot/demos.py
@@ -957,7 +957,7 @@ def show_colors(*, nhues=17, minsat=10, unknown="User", include=None, ignore=Non
             names = np.array([name for ipairs in hclpairs for name, _ in ipairs])
             ncols, nrows = 4, len(names) // 4 + 1
 
-        names.resize((ncols, nrows))  # fill empty slots with empty string
+        names = np.resize(names, (ncols, nrows))  # fill empty slots with empty string
         namess[cat] = names
 
     # Draw figures for different groups of colors
diff --git a/ultraplot/tests/test_demos.py b/ultraplot/tests/test_demos.py
new file mode 100644
index 000000000..ebaf9a24d
--- /dev/null
+++ b/ultraplot/tests/test_demos.py
@@ -0,0 +1,114 @@
+import numpy as np, pytest, ultraplot as plt
+import matplotlib.font_manager as mfonts
+import ultraplot.demos as demos
+
+
+def test_show_channels_requires_arg():
+    """show_channels should raise when no positional colormap is provided."""
+    with pytest.raises(ValueError):
+        demos.show_channels()
+
+
+@pytest.mark.mpl_image_compare
+def test_show_channels_basic():
+    """Basic invocation of show_channels returns a figure and axes of expected length."""
+    # Request fewer samples and fewer channels to keep the figure small
+    fig, axs = demos.show_channels("viridis", N=20, saturation=False, rgb=False)
+    # Expect three channel plots: Hue, Chroma, Luminance
+    assert fig is not None
+    assert hasattr(axs, "__len__")
+    assert len(axs) == 3
+    # Each axis should have a title set
+    for ax in axs:
+        assert isinstance(ax.get_title(), str)
+    return fig
+
+
+@pytest.mark.mpl_image_compare
+def test_show_colorspaces_default_and_options():
+    """show_colorspaces should create three panels (hcl/hsl/hpl)."""
+    fig, axs = demos.show_colorspaces()
+    assert fig is not None
+    assert hasattr(axs, "__len__")
+    assert len(axs) == 3
+    # Titles should include the space names
+    titles = [ax.get_title().upper() for ax in axs]
+    assert any("HCL" in t or "HSL" in t or "HPL" in t for t in titles)
+    return fig
+
+
+@pytest.mark.parametrize("demo", ["show_cmaps", "show_cycles"])
+@pytest.mark.mpl_image_compare
+def test_show_cmaps_and_cycles_return_fig_and_axes(demo):
+    """show_cmaps and show_cycles should return a figure and axes collection."""
+    fig, axs = getattr(demos, demo)()
+    assert fig is not None
+    assert hasattr(axs, "__len__")
+    assert len(axs) > 0
+    # Return a figure for image comparison (use the colormap figure)
+    return fig
+
+
+def test__filter_colors_behavior():
+    """Unit tests for the color filtering helper."""
+    # When ihue == 0, function should return True for gray colors (sat <= minsat)
+    hcl_gray = (10.0, 5.0, 50.0)  # hue, sat, lum
+    assert demos._filter_colors(hcl_gray, ihue=0, nhues=8, minsat=10)
+
+    # Non-gray color should be filtered according to hue buckets
+    nhues = 4
+    hcl_color = (100.0, 50.0, 50.0)
+    breakpoints = np.linspace(0, 360, nhues)
+    found = False
+    for ihue in range(1, nhues):
+        low = breakpoints[ihue - 1]
+        high = breakpoints[ihue]
+        if low <= hcl_color[0] < high or (ihue == nhues - 1 and hcl_color[0] == high):
+            assert demos._filter_colors(hcl_color, ihue=ihue, nhues=nhues, minsat=10)
+            found = True
+            break
+    assert found, "Did not find a matching hue interval for the test hue"
+
+    # Hue at the endpoint should be included for last bucket
+    hcl_endpoint = (360.0, 50.0, 50.0)
+    # For nhues=4 the last bucket index is 3; the endpoint logic should include it
+    assert not demos._filter_colors(hcl_endpoint, ihue=3, nhues=4, minsat=10)
+
+
+@pytest.mark.mpl_image_compare
+@pytest.mark.parametrize("nhues,minsat", [(4, 10), (8, 15)])
+def test_show_colors_basic_and_titles(nhues, minsat):
+    """show_colors generates axes with titles for requested categories."""
+    # Use parameterized nhues/minsat to exercise behavior deterministically
+    fig, axs = demos.show_colors(nhues=nhues, minsat=minsat)
+    assert fig is not None
+    assert hasattr(axs, "__len__")
+    assert len(axs) > 0
+    for ax in axs:
+        # Titles should be non-empty strings (e.g., "CSS4 colors", "Base colors", ...)
+        title = ax.get_title()
+        assert isinstance(title, str)
+        assert title != ""
+    return fig
+
+
+@pytest.mark.mpl_image_compare
+def test_show_fonts_with_existing_font():
+    """show_fonts should accept a real font name from the system and return a figure."""
+    # Pick a font that is available in the matplotlib font manager
+    ttflist = mfonts.fontManager.ttflist
+    # If no fonts are present, skip the test
+    if not ttflist:
+        pytest.skip("No system fonts available for testing show_fonts.")
+    font_name = ttflist[0].name
+    fig, axs = demos.show_fonts(font_name)
+    assert fig is not None
+    # When a single font is requested, we expect a single row (len(props)) of axes
+    assert hasattr(axs, "__len__")
+    assert len(axs) >= 1
+    # Basic sanity: each axis should contain at least one text artist
+    for ax in axs:
+        texts = ax.texts
+        assert hasattr(texts, "__len__")
+        assert len(texts) >= 1
+    return fig