Doctest doesn't find new function

edit

I thought that I would fix gihub bug #22313 (Implement Euler Polynomials)

So I added a function (boiled down, the implementation here is obviously incorrect)

def euler_polynomial(x, n):
    r"""
    Compute the value of the ``n``-th Euler polynomial at ``x``.

    TESTS::

        sage: y=QQ['y'].gen()
        sage: euler_polynomial(y, 0)
        1
    """
    return 1

Now if I run ./sage -t src/sage/combinat/combinat.py I get

[...]
      File "<doctest sage.combinat.combinat.euler_polynomial[1]>", line 1, in <module>
        euler_polynomial(y, Integer(0))
        ^^^^^^^^^^^^^^^^
    NameError: name 'euler_polynomial' is not defined
**********************************************************************
1 item had failures:
   1 of   3 in sage.combinat.combinat.euler_polynomial
    [462 tests, 1 failure, 2.38 s]

I am obviously doing something wrong, but am at a loss as to what. I have tried rebuilding sage.