PHP random tests seem to be off as well.

For: -12dy+9yzd-9dyz-13y+8y-1-11yd+15yd+9y
it expects: 4y-8dy-10dyz

The "1" term should not be there according to the description and the test result makes no sense as a result.

with 1->10, 2->0 result will be 0325833691764184 => 325833691764184
while with 1 ->0, 2->10 result will become 258336917-3-064184

Important point is : it is not swapping of two number but only the number at position 1 is moved to position 2.
In case of 209917 i,j are next to each other so moving digit at position 1 to 2 looks like a swap but it is not.

With PHP and for input of 3258336917064184 I get a failed test:

Expected: Array (
0 => 325833691764184
1 => 10
2 => 0
)
Actual : Array (
0 => 325833691764184
1 => 0
2 => 10
)

By the logic of the 209917 example it should be 0,10 and not 10,0 for the i,j combo.
Seems wrong to me. Am I missing something here?