Keep tests in json format

So the results are typed
2020-08-24 18:37:55 +02:00
parent d592cc3050
commit 4d280e02b0
55 changed files with 55 additions and 329 deletions
--- a/tests_dir/select_join_opt.result
+++ b/tests_dir/select_join_opt.result
@@ -1,3 +1 @@
-id,name,chief,age,skill
-0,jack,0,22,C
-4,eve,0,25,C
+{"content": [[4, "eve", 0, 25, "C"], [0, "jack", 0, 22, "C"]], "header": ["id", "name", "chief", "age", "skill"]}