[ENH] add CI test for unwanted files (#369)

.github/workflows/test_update_leaderboard.yml

@@ -30,4 +30,7 @@ jobs:
         run: python docs/format_sample_sheets.py
 
       - name: Update leaderboard
-        run: python docs/format_export_leaderboards.py
+        run: python docs/format_export_leaderboards.py
+
+      - name: Run check for unwanted PR files
+        run: python docs/check_unwanted_files.py

docs/check_unwanted_files.py

@@ -0,0 +1,12 @@
+from pathlib import Path
+
+CURRENT_DIR = Path(__file__).parents[1]
+RESULTS_DIR = CURRENT_DIR / "results"
+
+# make sure that there are no files `results/**/reference_outputs.json`
+# nor `results/**/leaderboard.csv`
+matched_files = []
+for filename in ["reference_outputs.json", "leaderboard.csv"]:
+    matched_files += list(RESULTS_DIR.glob(f"**/{filename}"))
+
+assert len(matched_files) == 0, f"The following files should not be present: {matched_files}"