Drivers side headlights do not work, light bulbs, fuses look good, what else?

The battery in my truck "looks good" but after *TESTING* it is dead as a hammer! .. Fuses need to be tested using a test light or volt meter with headlights on .. Headlight bulb can be tested with an ohmmeter .. Voltage TO the headlight bulb can be tested using the test light or the volt meter ... Testing seems to be the key!