adding futher unit tests with alcotest

test/test_ast.ml

@@ -0,0 +1,15 @@
+open Ast
+
+let parse query = 
+  let lexbuf = Lexing.from_string query in
+  Parser.main Lexer.read_token lexbuf
+
+let equal_ast ast1 ast2 = 
+  ast1 = ast2
+
+let 
+
+let test_simple_select() =
+  let q1 = parse "SELECT a FROM t" in
+  let ast1 = Query(Select([Column("a")], [Table("t")])) in
+  Alcotest.(check