It doesn't have two hot wires, or shouldn't. It should have only one continuous hot, and one switch leg.
Standard switches do not get a neutral. If you think switches work with a neutral, you need to seriously re-evaluate your knowledge of electricity, or hire a professional and leave your experimentation and discovery to safe lower voltage where you will do little harm.
Depending on how the circuit is wired, you may have a power cable (hot+neutral) to the fixture, and a switchleg cable (hot+ switchleg) to the switch (in which the white wire should be marked, and be the continuous hot), or power cable to the switch box, with a switched cable to the fixture. In that case the whites in the switch box are connect together and tucked into the rear.
For a proper tester, you should get a Wiggy (trade name), which applies some load. A neon tester can show false positives due to current leakage.