Drive eight LEDs with a pattern chosen by a 3-bit selector: 000 all off, 001 all on, 010 alternating 10101010, 011 alternating 01010101, 100 upper half 11110000, 101 lower half 00001111, 110 outer pair 10000001, 111 inner pair 00011000. Input: sel, 3 bits. Output: leds, 8 bits. The testbench applies all eight selections.