Far as I know, from Japan handling the Diamond Princess passengers, the tests are 75% accurate.
If you test positive, you should have 3 negative tests in a row, i.e. one per day for 3 days in a row.
If you test positive in that time, reset, wait a few days before the next round of tests.
Same “should” be applied for testing positive IF one suspects you have the virus, yet the test shows negative.
The above is assuming the Chinese tests are not used.