plpgsql: calling a function with 2 OUT parameters

SELECT * INTO xx, yy FROM get_test();

UPDATE:

Explanation:

Modifying the second function:

CREATE OR REPLACE FUNCTION get_test_read()
RETURNS VOID AS $$
DECLARE
   xx text;
   yy text;
BEGIN

   SELECT * INTO xx, yy FROM get_test();
   
   RAISE INFO 'x: <%>', xx;
   RAISE INFO 'y: <%>', yy;

END;
$$  LANGUAGE plpgsql;  

This is similar to SELECT INTO with TABLE, where only get 2 values:

SELECT "FIELD1", "FIELD2" INTO variable1, variable2 FROM "TABLE" WHERE ...

Npgsql Basic Usage

PL/pgSQL Function Parameter Modes: IN, OUT, INOUT

As you have 2 OUT params, your function will return a record.

In order to get all values you should use function as the source of your data and put it into the FROM clause like this:

SELECT * FROM get_test() INTO xx, yy;