Incorrect nonterminals/terminals in the testset.
Consider the G4 grammar here https://git.scc.kit.edu/IPDSnelting/first_follow/-/blob/master/first_follow_test.py#L64 and the G5 grammar here https://git.scc.kit.edu/IPDSnelting/first_follow/-/blob/master/first_follow_test.py#L75
The productions do not have a "y" terminal, but the list of terminals says they do.
Something similar can be observed with the G8 grammar here: https://git.scc.kit.edu/IPDSnelting/first_follow/-/blob/master/first_follow_test.py#L128
The productions don't have an F or T' nonterminal, but the list of nonterminals has them. Furthermore, the list of terminals contains a '*' terminal, but the productions never refers to such a terminal.