But part of the test is the cumulative fatigue. If bump up your FTP for the start then you will ride less time to failure but the results will be totally skewed.
Just do the test as presented, get a result and move on to the next training block.
You don’t train for FTP tests, you train to get fit and or faster. This occurs over time, and over time your fitness level fluctuates and so too will your FTP. So let it.
People put far too much emphasis on their FTP when on any given day, what you had for breakfast can be far more impactful on your performance.
It’s just a step in many. Don’t game it.