test bench

You must change your two processes:

• Make a process for the clock:

Clock_Process: PROCESS
BEGIN
  clock <= '0';
  WAIT FOR 50 ns;
  clock <= '1';
  WAIT FOR 50 ns;
  -- Do not put 'WAIT;' as it will force the process
  -- to wait forever and consequently, clock will never toggle.
END PROCESS;

• Make a process for the reset:

Reset_Process: PROCESS
BEGIN
  Resetn <= '0'; -- Active low reset
  WAIT FOR 201 ns;  -- Maintain low reset during 201ns
  Resetn <= '1';  -- Release resetn
  WAIT;
END PROCESS;

• Make a process for the input data:

always : PROCESS                                             
-- optional sensitivity list                                  
( clock  )                                                 
BEGIN                                                         
  -- code executes for every event on sensitivity list 
  carry_in <= '0';  -- First carry_in value (input of your block)
  D <= "1101";   -- First D value (input of your block)
  wait for 300ns;
  wait until rising_edge(clock); -- wait until rising edge of clock
  wait for 1ns; -- Just to model the Tco of flip-flop
  carry_in <= '0';  -- Second carry_in value (input of your block)
  D <= "1101"; -- SecondD value (input of your block)
  wait;  -- You can use this as this is the last data of your test bench
END PROCESS always;