SQL & PL/SQL

I am using Oracle 10GR2 and a new user for plsql

I want to write a plsql block or SQL in order to insert some dummy data.
I want to use the column list from all_tab_columns and want to construct insert statement

EX: I am trying to construct SQL as below

for i in (select column_name from all_tab_columns where table_name='EMP')
loop
v_sql := insert into emptest valuesi.column_name

could you please let me know any pointer for the same ..?
can I use any other technique for the same .. like collection, nested table etc