Why wont the light turn on on my 1989 honda civic hatchback dx?

i have a 1989 honda civic hatchback and some of the headlights won't turn on. i checked all the fuses and they are all good. my parking and corner lights wont come on, both high beams work and only the driver side light works. i have a tester and when i test it it won't work (the headlights are good) but i took off the plug and tried it and the plug is still good. i think it might be some of the wiring but it all looks good under the hood. i haven't taken off the dash yet and i think it might be the switch. but before i waste time can you tell me what it might be?