CREATE OR REPLACE FUNCTION test.test_common_set_and_protect_created_at_timestamp() RETURNS VOID AS $$
DECLARE
  v_exception_raised BOOLEAN;
BEGIN
  CREATE TABLE test.test (created_at TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP, dummy TEXT);
  CREATE TRIGGER auto1 BEFORE INSERT OR UPDATE ON test.test
    FOR EACH ROW EXECUTE PROCEDURE common.set_and_protect_created_at_timestamp();

  INSERT INTO test.test (dummy) VALUES ('bla');

  IF (SELECT created_at != CURRENT_TIMESTAMP FROM test.test) THEN
    RAISE EXCEPTION 'created_at timestamp does not equal CURRENT_TIMESTAMP.';
  END IF;

  
  
  <<test_inserting_of_wrong_timestamp>>
  BEGIN
    v_exception_raised := false;
    INSERT INTO test.test (created_at) VALUES ('2000-01-01');    
  EXCEPTION WHEN raise_exception THEN v_exception_raised := true; END;
  
  PERFORM test.assert(v_exception_raised, 'Inserting a wrong created_at timestamp should not be possible.');
  
  

  <<test_updating_timestamp>>
  BEGIN
    v_exception_raised := false;
    UPDATE test.test SET created_at = '2000-01-01';
  EXCEPTION WHEN raise_exception THEN v_exception_raised := true; END;
  
  PERFORM test.assert(v_exception_raised, 'Changing a created_at timstamp during an update should not be possible.');
END;
$$ LANGUAGE plpgsql;