Yep. The code will indeed go into an infinite recursion if n is less than 1 (negative number or 0), resulting in a stack overflow error.

Either the tests are lacking or that was added after the translation was made and it wasn't added to the tests.

surprising that this works, i thougt it cal also be written as "three fifty" as per the description?

Doesn't this go into an infinite loop if I put in ) or any negative number?
if n == 0 then we call 0 + triangular(-1) and so on and so forth.

Fails for empty string.

Doesn't work for negative input!

In the description, step 4 is still missing the S for siblings.

i.e.
4. FLAMES --> 1>F 2>L 3>A 4>M 5>E 6>S

6>S is missing

For java the feedback on the test is flipped. When you return 6 it prints:

expected:<6> but was:<8>