Added zero flag to ALU and updated testbench to not fail because of it. TODO: Add cases to test the zero flag

tests/alu_tb.sv

@@ -16,14 +16,14 @@ module alu_tb #(width=2)();
     logic [2**width-1:0] A_in;
     logic [2**width-1:0] B_in;
     logic [2**width-1:0] Y_out;
-    logic [1:0] flags_out;
+    logic [2:0] flags_out;
 
     localparam int NUM_TESTS = 28;
     logic [3:0] ops[NUM_TESTS];
     logic [2**width-1:0] A_cases[NUM_TESTS];
     logic [2**width-1:0] B_cases[NUM_TESTS];
     logic [2**width-1:0] Y_exp[NUM_TESTS];
-    logic [1:0] flags_exp[NUM_TESTS];
+    logic [2:0] flags_exp[NUM_TESTS];
 
     alu #(width) dut (op_in, A_in, B_in, Y_out, flags_out);