diff --git a/tests/test_optional/test_utils/test_data_utils.py b/tests/test_optional/test_utils/test_data_utils.py
new file mode 100644
index 0000000000..97fd3a41f1
--- /dev/null
+++ b/tests/test_optional/test_utils/test_data_utils.py
@@ -0,0 +1,49 @@
+"""
+Tests for _plotly_utils.data_utils.image_array_to_data_uri.
+
+Uses the pypng backend so the tests do not require Pillow.
+"""
+
+import numpy as np
+import pytest
+
+from _plotly_utils.data_utils import image_array_to_data_uri
+
+PNG_PREFIX = "data:image/png;base64,"
+
+
+def test_greyscale_array_returns_png_data_uri():
+    img = np.zeros((2, 2), dtype=np.uint8)
+    uri = image_array_to_data_uri(img, backend="pypng")
+    assert uri.startswith(PNG_PREFIX)
+
+
+def test_rgb_array_returns_png_data_uri():
+    img = np.zeros((2, 2, 3), dtype=np.uint8)
+    uri = image_array_to_data_uri(img, backend="pypng")
+    assert uri.startswith(PNG_PREFIX)
+
+
+def test_rgba_array_returns_png_data_uri():
+    img = np.zeros((2, 2, 4), dtype=np.uint8)
+    uri = image_array_to_data_uri(img, backend="pypng")
+    assert uri.startswith(PNG_PREFIX)
+
+
+@pytest.mark.parametrize("compression", [-1, 10])
+def test_invalid_compression_raises(compression):
+    img = np.zeros((2, 2), dtype=np.uint8)
+    with pytest.raises(ValueError, match="compression level"):
+        image_array_to_data_uri(img, backend="pypng", compression=compression)
+
+
+def test_invalid_shape_raises():
+    img = np.zeros(5, dtype=np.uint8)
+    with pytest.raises(ValueError, match="Invalid image shape"):
+        image_array_to_data_uri(img, backend="pypng")
+
+
+def test_jpg_without_pil_backend_raises():
+    img = np.zeros((2, 2), dtype=np.uint8)
+    with pytest.raises(ValueError, match="jpg binary strings"):
+        image_array_to_data_uri(img, backend="pypng", ext="jpg")