Postgres - Permissions within the function

I'm setting up a system where the user will have very limited access, just view and perform certain specific functions.

Scenario (with root user)

It has three tables:

• Person
• Device
• Access

And three 4 functions:

• sync_person ()
• sync_device ()
• sync_access ()
• sync_access_user ()

Desired (with normal user)

The user should only be able to:

• table person - Query ( SELECT )
• sync_person () - Run
• sync_device () - Run
• sync_access_user () - Run

Problem

Functions are generating permission error for internal executions.

Hypothetical scenario (Created by root)

CREATE TABLE test(
    name    VARCHAR
);

CREATE OR REPLACE FUNCTION test(
    name    VARCHAR
) RETURNS BOOLEAN AS $func$
    BEGIN
        INSERT INTO test VALUES (name);
        RETURN TRUE;
    END;
$func$ LANGUAGE plpgsql;

GRANT EXECUTE ON FUNCTION test(VARCHAR) TO normal_user;

Execution (Normal user)

SELECT test('Temwifi');

ERROR: permission denied for relation test
SQL state: 42501
Context: SQL statement "INSERT INTO test VALUES (name)"
PL/pgSQL function test(character varying) line 3 at SQL statement

Question

• How to allow the normal user to perform the function, without releasing direct access to the required resources? Ex: INSERT