diff --git a/tests/21_json_pretty.out b/tests/21_json_pretty.out
new file mode 100644
index 0000000..4345cac
--- /dev/null
+++ b/tests/21_json_pretty.out
@@ -0,0 +1,8 @@
+{
+  "a": 1,
+  "b": 2,
+  "nums": [
+    10,
+    20
+  ]
+}