I’m not feeling well, but I think it’s just a cold, because I tested negative for the virus. Should I go to an outdoor gathering?

No. A negative test isn’t enough to reassure you that you don’t have the virus, especially if you have symptoms. The most common coronavirus test, a PCR test, can confirm only that you do have the virus, but it can’t ensure that you definitely don’t.

If you’re not feeling sick, is it morally defensible to get a coronavirus test in order to see family, given testing shortages?

In many cases, no. Sick people need those tests, and so do essential workers. They don’t need to be waiting in a three-hour-long line between shifts to get tested. That said, there are situations in which people may have an urgent need to see one another this winter. The most obvious example is when someone is terminally ill or unable to care for themselves, or they are especially isolated and depressed. If you’re fortunate to not fall in any of those categories, and seeing family can wait until the spring or summer, do that. Leave the tests for those who need them.