diff --git a/_data/activity/2000-01-01-software.yml b/_data/activity/2000-01-01-software.yml
new file mode 100644
index 0000000..137af59
--- /dev/null
+++ b/_data/activity/2000-01-01-software.yml
@@ -0,0 +1,4 @@
+# Activity feed self-test. The website's data check must reject this file,
+# because it holds no entries, so this PR must not merge. The workflow
+# closes it and deletes its branch.
+[]