test(client): add JSON flag fixture

Author: loong10k

src/test/resources/json-when-flag.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+for arg in "$@"; do
+  if [ "$arg" = "--json" ]; then
+    printf '%s\n' '{"type":"done","message":"json-enabled"}'
+    exit 0
+  fi
+done
+printf '%s\n' 'not-json'