HIV transmission is not so easy; last I checked, the rough odds of transmission from a single act of unprotected vaginal sex with a HIV+ partner was around 1 in 500.
If the test is 99% accurate, and your partner isn't in an obvious high risk group, it may push the odds into "less risky than other behaviors you commonly accept" territory.
In developed countries most HIV transmission is due to anal sex between men who have sex with men, where the odds of transmission per single act are more like 1 in 30. The transmission is much more heterosexual in Africa however, where most of this resistance is happening. [1] I'm kind of confused about the sexual practices that could cause this to happen, but I'm sure prostitution and rape (which increases transmission odds due to trauma) are involved.
What is your source for the 1 in 500? The numbers I found on the same website indicate an even smaller risk
https://www.catie.ca/en/pif/summer-2012/putting-number-it-ri...
However, "As you can imagine, accurately tracking the number of times a person is exposed to HIV is very difficult".
I don't recall; the numbers on Catie (~1 in 1250) are more modern and certainly a better estimate.
Either way, you only have to add a few more digits of risk mitigation and you're more likely to die in a car accident. A test that had even a 1% false negative rate would cover most of that ground.
HIV transmission is not so easy; last I checked, the rough odds of transmission from a single act of unprotected vaginal sex with a HIV+ partner was around 1 in 500.
If the test is 99% accurate, and your partner isn't in an obvious high risk group, it may push the odds into "less risky than other behaviors you commonly accept" territory.
For point of reference, condom use only decreases the risk by a factor of 10. Possibly less: https://www.catie.ca/en/fact-sheets/prevention/condoms