How are we supposed to know if we've been in contact with a positive case since they aren't testing people?

You don’t know : Without testing , you don’t know if you have been in contact with a covid19 infected person. Testing can be PCR or antibody testing.

You can't tell: This is why you must be conscientious about wearing a mask when you cannot be at least 6 feet from others outdoors and whenever you're in a public place indoors. Also wash hands with soap and water for 20 seconds or use sanitizer whenever you handle objects outside your house. Wash fruits. Disinfect outer packages of groceries, etc. Do the best you can.