def test_head_nonempty_dict():
""" Verify that head of nonempty dictionary is non-exceptional. """
head({"a": 1, "b": 2})
def test_head_nonempty_set():
""" Verify that head of nonempty set is non-exceptional. """
head({-1, 0, 1})
def test_head_nonempty_sequential_collection(h, xs, seqtype, iter_cast):
""" Verify accuracy of request for first element from nonempty Iterable. """
c = seqtype([h]) + seqtype(xs)
assert h == head(iter_cast(c))
def test_head_empty_collection(coll):
""" Request for first element from an empty Iterable is exceptional. """
with pytest.raises(ValueError):
head(coll)
def test_head_empty_string():
""" Empty string is exception to exceptional-ness of empty collection. """
assert "" == head("")
def test_head_atomic(obj):
""" head() of an atomic object is the object itself. """
assert obj == head(obj)