使用夹具返回值作为 mark.parametrize() 中的值 [英] using fixture return value as value in mark.parametrize()

问题描述

我的问题是 - 是否可以将夹具的返回值用作参数化中的值?问题是 - 我想动态获取可能的值(例如，虚拟服务器上的可用系统)以进行参数化.当其中一个装置创建虚拟服务器时，我可以访问这些.测试看起来像这样(伪代码):

my question is - is it possible to use return value from fixture as a value in parametrize? The problem is - I'd like to dynamically get possible values (for example, available systems on a virtual server) for parametrize. I can access these when a virtual server is created by one of the fixtures. Tests look like this (pseudo-code-ish):

[conftest.py]

@pytest_fixture(scope='session')
def test_server(request):
    test_server = Server([default_params])
    test_server.add()
    def fin():
        test_server.delete()
    request_addfinalizer(fin)
    return test_server()

[tests.py]

def test_basic_server(test_server):
    systems = test.server.get_available_systems()
    for system in systems:
        test_server.install(system)
        test_server.run_checks()
        test_server.uninstall(system)

def test_other(test_server):
    [other tests]

etc

这样，为每个会话添加一个服务器，然后在其上运行所有测试，会话结束后，服务器被删除.但是有没有办法使用会话开始时添加的服务器方法来获取@pytest.mark.parametrize 中的可用系统而无需明确列出它们(静态地作为参数中的列表)?这样每个系统都会在单独的测试中运行.

This way, one server is added for each session, then all tests run on it, and after session ends, server is removed. But is there a way to get the available systems in @pytest.mark.parametrize without explicitly listing them (statically as a list in parametrize), using the method from server that is added when the session begins? That way each system would run in a separate test.

我尝试在另一个夹具中使用 test_server 然后返回列表(与 test_server 夹具返回 test_server 的方式相同，但我不能将其用作参数化中的值 - 因为在任何测试中调用 test_server 夹具之前对装饰器进行评估，获取列表取决于 test_server 夹具.

I tried using test_server in another fixture and then returning the list (the same way test_server is returned by test_server fixture, but I cannot use that as a value in parametrize - since decorator is evaluated before the test_server fixture is called in any test, and getting the list depends on test_server fixture.

这将是理想的:

[tests.py]

@pytest.mark.parametrize('system',[systems_list <- dynamically generated
                                             when the server is created])

def test_basic_server(test_server,system):
    test_server.install(system)
    test_server.run_checks()
    test_server.uninstall(system)

这只是一个非常基本的例子，在我的测试中，我需要基于多个场景和值进行参数化，而当我静态执行时，我最终得到了巨大的数组.

This is just a very basic example, in my tests I need to parametrize based on multiple scenarios and values and I end up with giant arrays when I do it statically.

但原理保持不变 - 基本上:我可以在使用此夹具运行的第一次测试之前调用夹具，或者 pytest.mark.parametrize() 如何访问夹具值?

But the principle remains the same - basically: can I call the fixture before the first test using this fixture runs, or how can pytest.mark.parametrize() access fixture values?

推荐答案

我认为您可能无法直接实现您想要的.因为@pytest.mark.parametrize是在采集过程中被调用的，而fixtures会在采集完成后被调用.

I think you may be unable to achieve what you want directly. Because @pytest.mark.parametrize is being called during collecting, and fixtures will be called after collection completed.

但我有另一种方法来实现类似的结果，主要是通过扩展 pytest 插件 pytest_generate_tests 和使用方法 metafunc.parametrize.https://pytest.org/latest/parametrize.html#basic-pytest-generate-tests-example

But I have an alternative way to achieve similar result, mainly by extending pytest plugin pytest_generate_tests and using method metafunc.parametrize. https://pytest.org/latest/parametrize.html#basic-pytest-generate-tests-example

这是我的解决方案.在 conftest.py

Here is my solution. In conftest.py

class System(object):
    def __init__(self, name):
        self.name = name

    def __repr__(self):
        return "<System '{}'>".format(self.name)

def get_available_systems():
    return [System('A'), System('B'), System('C')]


def pytest_generate_tests(metafunc):
    if 'system' in metafunc.fixturenames:
        available_systems = get_available_systems()

        metafunc.parametrize('system', available_systems)

在测试文件中:

def test_basic_server(system):
    print(system)

这是输出，您将可以访问测试中的每个系统.

This is the output, you will have access to each system in test.

collected 3 items

test_01.py::test_basic_server[system0] <System 'A'>
PASSED
test_01.py::test_basic_server[system1] <System 'B'>
PASSED
test_01.py::test_basic_server[system2] <System 'C'>
PASSED

不好的是，每次使用fixture system 时都会调用get_available_systems，这不是您想要的.但是我觉得添加一些额外的逻辑让查询逻辑只执行一次也不难.

The bad thing is, get_available_systems will be called every time whenever using fixture system, which is not what you want. But I think it's not hard to add some extra logic to make the query logic only be executed once.

例如:

def pytest_generate_tests(metafunc):
    if 'system' in metafunc.fixturenames:
        if hasattr(metafunc.config, 'available_systems'):
            available_systems = metafunc.config.available_systems
        else:
            available_systems = get_available_systems()
            metafunc.config.available_systems = available_systems
        metafunc.parametrize('system', available_systems)

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