Add prototype test that we want to fail, which currently doesn't.
diff --git a/regress/open_filename_duplicate_consistency.test b/regress/open_filename_duplicate_consistency.test
new file mode 100644
index 0000000..a997972
--- /dev/null
+++ b/regress/open_filename_duplicate_consistency.test
@@ -0,0 +1,6 @@
+# zip_open: file opens fine even though same file name appears twice
+program tryopen
+args -c filename_duplicate.zip
+return 0
+file filename_duplicate.zip filename_duplicate.zip filename_duplicate.zip
+stderr some error about a duplicate file name
