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.result
+++ b/tests_dir/select_join.result
@@ -1,2 +1 @@
-id,skill,name,chief,age
-3,C++,dean,1,33
+{"content": [[3, "C++", "dean", 1, 33]], "header": ["id", "skill", "name", "chief", "age"]}