library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity Tester is port(
    a, b: in unsigned(15 downto 0);   -- two input numbers from ALU
	ia, ib: in unsigned(15 downto 0); -- two input numbers from I2C slaveIn
    ctrl: in unsigned(3 downto 0);    -- opcode from ALU
    ictrl: in unsigned(3 downto 0);   -- opcode from I2C slaveIn
    r: in unsigned(15 downto 0);     -- result from ALU
	ir: in unsigned(15 downto 0);     -- result from I2C slaveOut
	error: out std_logic_vector(5 downto 0));  -- Tester output
end Tester;

architecture Tester_impl of Tester is
signal result : unsigned(15 downto 0);

begin
    with ictrl select
        result <= a + b               when X"0",  -- addition
             a - b               when X"1",  -- subtraction
             resize(a * b, 16)   when X"2",  -- multiplication
             a / b               when X"3",  -- division
             a + 1               when X"4",  -- increment
             a - 1               when X"5",  -- decrement
             not a               when X"6",  -- bitwise NOT
             a and b             when X"7",  -- bitwise AND
             a xor b             when X"8",  -- bitwise XOR
             a srl to_integer(b) when X"9",  -- shift right with zero padding
             a sll to_integer(b) when X"A",  -- shift left
             a ror to_integer(b) when X"B",  -- rotate right
             a rol to_integer(b) when X"C",  -- rotate left
             X"0000"             when others;

	-- input short
	error(0) <= '1' when (a /= ia and (a = b or a = ctrl)) or (b /= ib and (b = a or b = ctrl))
		else	'0';
		
	-- input open
	error(1) <= '1' when (a /= ia and a = X"0000") or (b /= ib and b = X"0000") or (ctrl /= ictrl and ctrl = X"0000")
		else	'0';
		
	-- output short
	error(2) <= '1' when (r /= ir) and (ir /= X"0000")
		else	'0';
		
	-- output open
	error(3) <= '1' when (r /= ir) and (ir = X"0000")
		else	'0';
		
	-- mathematic computation error
	error(4) <= '1' when (ictrl < X"6") and (r /= result)
		else	'0';
		
	-- logical operation error
	error(5) <= '1' when (ictrl > X"5") and (r /= result)
		else	'0';
end Tester_impl;