FitNessse Test can not find Fixture

import pytest

def my_fixture():
    data = {'x': 1, 'y': 2, 'z': 3}
    return data

def test_my_fixture(my_fixture):
    assert my_fixture['x'] == 1

  def test_my_fixture(my_fixture):
E       fixture 'my_fixture' not found
>       available fixtures: cache, capfd, capsys, doctest_namespace, monkeypatch, pytestconfig, record_xml_property, recwarn, tmpdir, tmpdir_factory
>       use 'pytest --fixtures [testpath]' for help on them.

import pytest

@pytest.fixture()
def my_fixture():
    data = {'x': 1, 'y': 2, 'z': 3}
    print('prepare')
    yield data
    print('destroy')

def test_my_fixture(my_fixture):
    print('test it')
    assert my_fixture['x'] == 1

import pytest

@pytest.fixture()
def my_fixture():
    print('prepare')
    # raise Exception('Oops')
    yield None
    print('destroy')

def test_my_fixture(my_fixture):
    # raise Exception('Booms!')
    print('test it')

======================================= test session starts ========================================
collected 1 item                                                                                    

t.py E

============================================== ERRORS ==============================================
________________________________ ERROR at setup of test_my_fixture _________________________________

    @pytest.fixture()
    def my_fixture():
        data = {'x': 1, 'y': 2, 'z': 3}
        print('prepare')
>       raise Exception('Oops')
E       Exception: Oops

t.py:7: Exception
===================================== 1 error in 0.03 seconds ======================================

======================================= test session starts ========================================
collected 1 item                                                                                    

t.py F

============================================= FAILURES =============================================
_________________________________________ test_my_fixture __________________________________________

my_fixture = {'x': 1, 'y': 2, 'z': 3}

    def test_my_fixture(my_fixture):
>       raise Exception('Booms!')
E       Exception: Booms!

t.py:12: Exception
===================================== 1 failed in 0.03 seconds =====================================