python - 使用 pytest-xdist 跨主节点和工作节点访问共享资源

Question

我试图在主节点和工作节点之间共享数据库中的随机条目列表(我对共享资源的定义)，并使用 pytest-xdist 并行化测试。我的代码遵循以下结构:

## in conftest.py
def get_db_entries():
   connect to db
   run a query with group by and random
   returns one random entry per group as a list of dictionaries.

我采纳了https://hackebrot.github.io/pytest-tricks/shared_directory_xdist/提供的建议在主节点和工作节点之间共享数据库条目:

# in conftest.py
def pytest_configure(config):
    if is_master(config):
        # share db_entries across master and worker nodes.
        config.db_samples = get_db_entries()

def pytest_configure_node(node):
    """xdist hook"""
    node.slaveinput['db_entries'] = node.config.db_samples

def is_master(config):
    """True if the code running the given pytest.config object is running in a xdist master
    node or not running xdist at all.
    """
    return not hasattr(config, 'slaveinput')

@pytest.fixture
def db_samples(request):
    """Returns a unique and temporary directory which can be shared by
    master or worker nodes in xdist runs.
    """
    if is_master(request.config):
        return request.config.db_samples
    else:
        return request.config.slaveinput['db_entries']

我可以使用上述方法在主机和工作人员之间共享这些数据库条目，如下所示:

# in test-db.py
def test_db(db_samples):
    for sample in samples:
       # test each sample.

到目前为止，测试用例还没有并行化。我只是在主节点和工作节点之间共享相同的数据库条目。

我的问题:如何参数化共享资源状态(数据库条目)，以便我可以使用 pytest-xdist 并行执行这些测试？

我想做一些类似的事情:

# in conftest.py
samples = db_samples() # will FAIL coz fixture can't be invoked directly.

@pytest.fixture(params=samples)
def get_sample(request):
   return request.param

# in test-db.py
def test_db(get_sample):
    # test one sample.

Answer 1

感谢@hoefling的建议，我能够使用pytest-xdist钩子(Hook)和pytest_generate_tests来获得一个可行的解决方案。

# in conftest.py
def pytest_configure(config):
    if is_master(config):
        # share db_entries across master and worker nodes.
        config.db_samples = get_db_entries()

def pytest_configure_node(node):
    """xdist hook"""
    node.slaveinput['db_entries'] = node.config.db_samples

def is_master(config):
    """True if the code running the given pytest.config object is running in a xdist master
    node or not running xdist at all.
    """
    return not hasattr(config, 'slaveinput')

def pytest_generate_tests(metafunc):
    if 'sample' in metafunc.fixturenames:
        if is_master(metafunc.config):
            samples = metafunc.config.db_samples
        else:
            samples = metafunc.config.slaveinput['db_entries']
        metafunc.parametrize("sample", samples)

@pytest.fixture
def sample(request):
    return request.param

# in test-db.py
def test_db(sample):
    # test one sample.

@hoefling 建议使用 pytest_generate_tests 钩子(Hook)是缺失的部分。使用这个钩子(Hook)来参数化测试 fixture 有助于解决这个问题。