If you test positive, you likely had it and can spread it. If you test negative, there is about a 40% of a false negative, but it also depends on when you were exposed, so you'll end up negative if you are outside the window... post symptom, you were probably outside the window.
This also depends on the test itself. When I got mine, I went to a place that was using a new form of the test, and it was bad enough that the testing company lost their contract (whether they were fudging numbers or not is debatable, I can't find any good information on it either).
At the end of the day, if you didn't go to a hospital and get diagnosed with covid, or had an antibody test after you recovered, you probably can't be certain.
Sorry, it's the best I could come up with after days of looking it up from multiple sources.