diff --git a/tests/patch/ruff/info.json b/tests/patch/ruff/info.json
new file mode 100644
index 0000000..03f4d40
--- /dev/null
+++ b/tests/patch/ruff/info.json
@@ -0,0 +1,3 @@
+{
+  "run": ["ruff.sh"]
+}
diff --git a/tests/patch/ruff/ruff.sh b/tests/patch/ruff/ruff.sh
new file mode 100755
index 0000000..fa25fde
--- /dev/null
+++ b/tests/patch/ruff/ruff.sh
@@ -0,0 +1,60 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+HEAD=$(git rev-parse HEAD)
+rc=0
+
+pr() {
+    echo " ====== $* ======" | tee -a /dev/stderr
+}
+
+# If it doesn't touch .py files, don't bother. Ignore deleted.
+if ! git show --diff-filter=AM --pretty="" --name-only "${HEAD}" | grep -q -E "\.py$"
+then
+    echo "No python scripts touched, skip" >&"$DESC_FD"
+    exit 0
+fi
+
+ruff --version || exit 1
+
+tmpfile_o=$(mktemp)
+tmpfile_n=$(mktemp)
+
+echo "Redirect to $tmpfile_o and $tmpfile_n"
+
+echo "Tree base:"
+git log -1 --pretty='%h ("%s")' HEAD~
+echo "Now at:"
+git log -1 --pretty='%h ("%s")' HEAD
+
+pr "Checking before the patch"
+git checkout -q HEAD~
+
+# Also ignore created, as not present in the parent commit
+for f in $(git show --diff-filter=M --pretty="" --name-only "${HEAD}" | grep -E "\.py$"); do
+    ruff check --output-format pylint "$f" | tee -a "$tmpfile_o"
+done
+
+incumbent=$(wc -l < "$tmpfile_o")
+
+pr "Checking the tree with the patch"
+git checkout -q "$HEAD"
+
+for f in $(git show --diff-filter=AM --pretty="" --name-only "${HEAD}" | grep -E "\.py$"); do
+    ruff check --output-format pylint "$f" | tee -a "$tmpfile_n"
+done
+
+current=$(wc -l < "$tmpfile_n")
+
+echo "Errors before: $incumbent ; this patch: $current" >&"$DESC_FD"
+
+if [ "$current" -gt "$incumbent" ]; then
+    echo "New errors added" 1>&2
+    diff -U 0 "$tmpfile_o" "$tmpfile_n" 1>&2
+
+    rc=1
+fi
+
+rm "$tmpfile_o" "$tmpfile_n"
+
+exit $rc