diff --git a/goodwe_controller/test_ci15_failproof.py b/goodwe_controller/test_ci15_failproof.py
new file mode 100644
index 0000000..098a273
--- /dev/null
+++ b/goodwe_controller/test_ci15_failproof.py
@@ -0,0 +1,9 @@
+"""CI-15 throwaway: a test that fails on purpose, to show a red file fails the job.
+Never merge this branch. (Mutation habit: see MUTATION.md - the pointer
+test_bytecode.py requires of every suite.)"""
+import sys
+
+for i in range(1, 51):
+    print(f"line {i} of 50 (only the last 40 should reach the log)")
+print("FAILED: deliberate CI-15 failure")
+sys.exit(1)