Answer:
The test to care for/about his father or the test to continue being compassionate to his father/family during the worst moments.
Step-by-step explanation:
Like Rabbi Eliahu’s son, Elie stops caring for his father during these trying times. The Rabbi's son abandoned his father during the death march from Buna. The test isn't an actual test but one that is an emotional or mental one to see if Eli is strong minded and/or compassionate enough to stick with his father.