Trust behaviors, not tests, if you want to play it safe with COVID-19. Tests can be misleading for a number of reasons:

1. You can accurately test negative today, but if you get exposed tomorrow, you may test positive by tomorrow (or within the next few days).

2. If you have very recently been exposed to COVID-19, the virus may still be incubating and there may not be enough viral load yet for a test to detect it. 

3. Different tests have different accuracy levels, both in terms of sensitivity (ability of the test to detect virus) and specificity (ability of test to detect the correct virus). No test is perfect and all have a chance of false negatives or positives. False negatives are more common and dangerous than a false positive.

4. In order for even highly accurate tests to detect infection, the test must be administered properly. Home tests in particular are at risk of "administration error" which can lead to a false negative.