Pytest not raising import exceptions for regular classes?

results

shangxiao ~/projects/test-pytest $ pytest
========================================================= test session starts =========================================================
platform darwin -- Python 3.6.2, pytest-5.0.0, py-1.8.0, pluggy-0.12.0
rootdir: /Users/shangxiao/projects/test-pytest
collected 1 item

test_foo.py F                                                                                                                   [100%]

============================================================== FAILURES ===============================================================
________________________________________________________ FooTestCase.test_foo _________________________________________________________

self = <test_foo.FooTestCase testMethod=test_foo>

    def test_foo(self):
>       foo = Foo()
E       NameError: name 'Foo' is not defined

test_foo.py:6: NameError
====================================================== 1 failed in 0.04 seconds =======================================================
shangxiao ~/projects/test-pytest $

test_bar.py

class BarTestCase:
    def test_bar(self):
        bar = Bar()
        assert True

test_foo.py

from unittest import TestCase


class FooTestCase(TestCase):
    def test_foo(self):
        foo = Foo()
        assert True