diff --git a/test/3pdata/fetch-webpsuite.sh b/test/3pdata/fetch-webpsuite.sh
new file mode 100755
index 00000000..cb0848ab
--- /dev/null
+++ b/test/3pdata/fetch-webpsuite.sh
@@ -0,0 +1,24 @@
+#!/bin/bash -eu
+# Copyright 2024 The Wuffs Authors.
+#
+# Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+# https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+# <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+# option. This file may not be copied, modified, or distributed
+# except according to those terms.
+#
+# SPDX-License-Identifier: Apache-2.0 OR MIT
+
+# ----------------
+
+# This script fetches libwebp's test data suite.
+
+if [ ! -e ../../wuffs-root-directory.txt ]; then
+  echo "$0 should be run from the Wuffs test/3pdata directory."
+  exit 1
+fi
+
+# Check out a specific commit (from July 2024).
+git clone --quiet https://github.com/webmproject/libwebp-test-data.git webpsuite
+cd webpsuite
+git reset --quiet --hard 260804d686f0491e0326a50eef491829dae09e9e
diff --git a/test/3pdata/nia-checksums-of-webpsuite.txt b/test/3pdata/nia-checksums-of-webpsuite.txt
new file mode 100644
index 00000000..f0417107
--- /dev/null
+++ b/test/3pdata/nia-checksums-of-webpsuite.txt
@@ -0,0 +1,55 @@
+# Generated by script/print-nia-checksums.sh
+OK. ca4c0038 test/3pdata/webpsuite/bad_palette_index.webp
+OK. 6fbda804 test/3pdata/webpsuite/color_cache_bits_11.webp
+BAD d338aed8 test/3pdata/webpsuite/dual_transform.webp
+OK. 1ef61f19 test/3pdata/webpsuite/grid.bmp
+OK. 33b7a1f3 test/3pdata/webpsuite/grid.pgm
+OK. f79224e7 test/3pdata/webpsuite/grid.png
+OK. 06b07a30 test/3pdata/webpsuite/grid.ppm
+OK. fce8fc76 test/3pdata/webpsuite/lossless1.webp
+OK. fce8fc76 test/3pdata/webpsuite/lossless2.webp
+OK. fce8fc76 test/3pdata/webpsuite/lossless3.webp
+OK. 4cbe795c test/3pdata/webpsuite/lossless4.webp
+OK. f8e3adf4 test/3pdata/webpsuite/lossless_big_random_alpha.webp
+OK. 289af407 test/3pdata/webpsuite/lossless_color_transform.bmp
+OK. 7b7c1ae6 test/3pdata/webpsuite/lossless_color_transform.pgm
+OK. 289af407 test/3pdata/webpsuite/lossless_color_transform.ppm
+OK. 289af407 test/3pdata/webpsuite/lossless_color_transform.webp
+OK. f79224e7 test/3pdata/webpsuite/lossless_vec_1_0.webp
+OK. f79224e7 test/3pdata/webpsuite/lossless_vec_1_1.webp
+OK. f79224e7 test/3pdata/webpsuite/lossless_vec_1_10.webp
+BAD df11692d test/3pdata/webpsuite/lossless_vec_1_11.webp
+OK. f79224e7 test/3pdata/webpsuite/lossless_vec_1_12.webp
+BAD df11692d test/3pdata/webpsuite/lossless_vec_1_13.webp
+OK. f79224e7 test/3pdata/webpsuite/lossless_vec_1_14.webp
+BAD df11692d test/3pdata/webpsuite/lossless_vec_1_15.webp
+OK. f79224e7 test/3pdata/webpsuite/lossless_vec_1_2.webp
+BAD df11692d test/3pdata/webpsuite/lossless_vec_1_3.webp
+OK. f79224e7 test/3pdata/webpsuite/lossless_vec_1_4.webp
+OK. f79224e7 test/3pdata/webpsuite/lossless_vec_1_5.webp
+OK. f79224e7 test/3pdata/webpsuite/lossless_vec_1_6.webp
+BAD df11692d test/3pdata/webpsuite/lossless_vec_1_7.webp
+OK. f79224e7 test/3pdata/webpsuite/lossless_vec_1_8.webp
+BAD df11692d test/3pdata/webpsuite/lossless_vec_1_9.webp
+OK. 6706e719 test/3pdata/webpsuite/lossless_vec_2_0.webp
+OK. 6706e719 test/3pdata/webpsuite/lossless_vec_2_1.webp
+OK. 6706e719 test/3pdata/webpsuite/lossless_vec_2_10.webp
+BAD 62adeb37 test/3pdata/webpsuite/lossless_vec_2_11.webp
+OK. 6706e719 test/3pdata/webpsuite/lossless_vec_2_12.webp
+BAD 62adeb37 test/3pdata/webpsuite/lossless_vec_2_13.webp
+OK. 6706e719 test/3pdata/webpsuite/lossless_vec_2_14.webp
+BAD 62adeb37 test/3pdata/webpsuite/lossless_vec_2_15.webp
+OK. 6706e719 test/3pdata/webpsuite/lossless_vec_2_2.webp
+BAD 62adeb37 test/3pdata/webpsuite/lossless_vec_2_3.webp
+OK. 6706e719 test/3pdata/webpsuite/lossless_vec_2_4.webp
+OK. 6706e719 test/3pdata/webpsuite/lossless_vec_2_5.webp
+OK. 6706e719 test/3pdata/webpsuite/lossless_vec_2_6.webp
+BAD 62adeb37 test/3pdata/webpsuite/lossless_vec_2_7.webp
+OK. 6706e719 test/3pdata/webpsuite/lossless_vec_2_8.webp
+BAD 62adeb37 test/3pdata/webpsuite/lossless_vec_2_9.webp
+OK. 6957defa test/3pdata/webpsuite/near_lossless_75.webp
+OK. 7c80a001 test/3pdata/webpsuite/one_color_no_palette.webp
+OK. 6706e719 test/3pdata/webpsuite/peak.bmp
+OK. 315bbd77 test/3pdata/webpsuite/peak.pgm
+OK. 6706e719 test/3pdata/webpsuite/peak.png
+OK. 6706e719 test/3pdata/webpsuite/peak.ppm