diff --git a/t/lib/bash/collect_mysql_info.sh b/t/lib/bash/collect_mysql_info.sh
index 4bb4557d..6bdfc5c2 100644
--- a/t/lib/bash/collect_mysql_info.sh
+++ b/t/lib/bash/collect_mysql_info.sh
@@ -85,6 +85,7 @@ is \
    "$cnf_file" \
    "/tmp/12345/my.sandbox.cnf" \
    "find_my_cnf_file gets the correct file"
+[ $? -ne 0 ] && diag "$p/mysqld-instances"
 
 res=$(find_my_cnf_file "$samples/ps-mysqld-001.txt")
 is "$res" "/tmp/12345/my.sandbox.cnf" "ps-mysqld-001.txt"
diff --git a/util/test-bash-functions b/util/test-bash-functions
index f456a4cb..2616c7c8 100755
--- a/util/test-bash-functions
+++ b/util/test-bash-functions
@@ -211,6 +211,17 @@ wait_for_files() {
    done
 }
 
+diag() {
+   if [ $# -eq 1 -a -f "$1" ]; then
+      echo "# $1:"
+      awk '{print "# " $0}' "$1"
+   else
+      for line in "$@"; do
+         echo "# $line"
+      done
+   fi
+}
+
 # ############################################################################
 # Script starts here
 # ############################################################################