if the line is 
```python
if sum > p0 * pop:
```
both ``percentile_test_min``and ''percentile_test_median``are now passing but ``percentile_test_max``not any more,
one solution could be to hijack the ``p0=1`` call and returning ``rank.maximum`` instead of ``percentile`` function 
it solves the special ``p0=1``case without introducing local test in the pixel loop.