// Test stimulus
    initial begin
        // Initialize inputs
        operand1 = 32'h12345678;
        operand2 = 32'h87654321;

        // Test LD (Load) operation
        operation_select = 5'b00001; // LD
        #20;
        
        // Test ADD operation
        operation_select = 5'b00011; // ADD
        operand1 = 32'h80000000; // Negative number
        operand2 = 32'h80000000; // Negative number
        #20;
        
        // Test SUB operation
        operation_select = 5'b00100; // SUB
        operand1 = 32'h12345678;
        operand2 = 32'h87654321;
        #20;
        
        // Test AND operation
        operation_select = 5'b00101; // AND
        operand1 = 32'hAAAAAAAA;
        operand2 = 32'h55555555;
        #20;
        
        // Test OR operation
        operation_select = 5'b00110; // OR
        operand1 = 32'hAAAAAAAA;
        operand2 = 32'h55555555;
        #20;
        
        // Test XOR operation
        operation_select = 5'b00111; // XOR
        operand1 = 32'hAAAAAAAA;
        operand2 = 32'h55555555;
        #20;
        
        // Test INV operation
        operation_select = 5'b01000; // INV
        operand1 = 32'h12345678;
        #20;
        
        // Test SHL operation
        operation_select = 5'b01001; // SHL
        operand1 = 32'h12345678;
        operand2 = 5'h05; // Shift by 5 bits
        #20;
        
        // Test SHR operation
        operation_select = 5'b01010; // SHR
        operand1 = 32'h12345678;
        operand2 = 5'h05; // Shift by 5 bits
        #20;
        
        // End simulation
        $finish;
    end

endmodule