Call a stored procedure with another in Oracle

Does anyone know of a way, or even if its possible, to call a stored procedure from within another? If so, how would you do it?

Here is my test code:

SET SERVEROUTPUT ON;

DROP PROCEDURE test_sp_1;
DROP PROCEDURE test_sp;

CREATE PROCEDURE test_sp
AS
BEGIN
    DBMS_OUTPUT.PUT_LINE('Test works');
END;
/

CREATE PROCEDURE test_sp_1
AS
BEGIN
    DBMS_OUTPUT.PUT_LINE('Testing');
    test_sp;
END;
/

CALL test_sp_1;