如何对单个测试中使用的多个夹具应用间接参数化？

Question

我想为单个测试间接地参数化多个装置，这与“对特定参数应用间接”下的pytest documentation中描述的非常相似

测试代码大致如下所示：

import pytest

@pytest.fixture
def getDataA(request):
    """Expensive method to call data A (utilizing request.param)"""
    if (request.param = "DetailedDataElementinA"):
        return True

@pytest.fixture
def getDataB(request):
    """Expensive method to call data B (utilizing request.param)"""
    if (request.param = "DetailedDataElementinB"):
        return True


@pytest.mark.parametrize("getDataA, getDataB ", ["DetailedDataElementinA", " DetailedDataElementinB"], indirect=["getDataA ", "getDataB"])
def test_comparedata(getDataA, getDataB):
    """Test that compares specific elements (detailed in request param) of two data sets"""
    assert(getDataA == getDataB)

我的问题是@pytest.mark.parametrize。pytest文档中的示例仅使用一个间接参数化，而我使用两个间接参数化。我尝试了几种不同的语法结构，但迄今为止我没有成功，我收到了如下错误消息：

• “E TypeError:Parameterize（）为参数获取了多个值 “间接的”
• 在“参数化”中，名称的数量必须相等 “值的数量”

有人知道哪种语法可能有效吗

Answer 1

使用indirect=['getDataA', 'getDataB']应该是可行的，因为它应该是pass a list or tuple of arguments’ names to ^{} for fixtures to indirectly parametrize。但是，根据您当前的代码：

@pytest.mark.parametrize("getDataA, getDataB ", ["DetailedDataElementinA", " DetailedDataElementinB"], indirect=["getDataA ", "getDataB"])
def test_comparedata(getDataA, getDataB):
    assert(getDataA == getDataB)

您有2个间接参数化装置，但在每次测试运行时，您只有1个参数值传递给它。^{}的第二个参数应该是要传递给每个测试运行上的每个夹具的参数值：

If N argnames were specified, argvalues must be a list of N-tuples, where each tuple-element specifies a value for its respective argname.

第一次运行将尝试将仅"DetailedDataElementinA"传递到2个装置中，并将失败：

test.py::test_comparedata: in "parametrize" the number of names (2):
  ['getDataA', 'getDataB']
must be equal to the number of values (22):
  DetailedDataElementinA

因为它期望每个装置有2个值，1

按照方法的描述，由于存在2个装置，因此每个装置需要2个-元组值，1个值

（这里我简化了示例fixture，使fixture只返回param值，然后让断言无法看到getDataA和getDataB的实际返回值）

@pytest.fixture
def getDataA(request):
    return request.param.replace('ThisWillBePassedTo', 'FixtureReceived')

@pytest.fixture
def getDataB(request):
    return request.param.replace('ThisWillBePassedTo', 'FixtureReceived')

@pytest.mark.parametrize(
    'getDataA, getDataB',
    [
        ('ThisWillBePassedToA-1', 'ThisWillBePassedToB-1'),
        ('ThisWillBePassedToA-2', 'ThisWillBePassedToB-2'),
        ('ThisWillBePassedToA-3', 'ThisWillBePassedToB-3'),
    ],
    indirect=['getDataA', 'getDataB'],
)
def test_comparedata(getDataA, getDataB):
    assert (getDataA == getDataB)

应该有3个测试（3个元组），每次运行时，索引[0]处的元组元素将传递给getDataA，索引[1]处的元组元素将传递给getDataB，顺序与定义夹具的顺序相同：

test.py::test_comparedata[ThisWillBePassedToA-1-ThisWillBePassedToB-1] FAILED [ 33%]
test.py::test_comparedata[ThisWillBePassedToA-2-ThisWillBePassedToB-2] FAILED [ 66%]
test.py::test_comparedata[ThisWillBePassedToA-3-ThisWillBePassedToB-3] FAILED [100%]

getDataA = 'FixtureReceivedA-1', getDataB = 'FixtureReceivedB-1'
>       assert (getDataA == getDataB)
E       AssertionError: assert 'FixtureReceivedA-1' == 'FixtureReceivedB-1'
E         - FixtureReceivedB-1
E         ?                ^
E         + FixtureReceivedA-1
E         ?     

getDataA = 'FixtureReceivedA-2', getDataB = 'FixtureReceivedB-2'
>       assert (getDataA == getDataB)
E       AssertionError: assert 'FixtureReceivedA-2' == 'FixtureReceivedB-2'
E         - FixtureReceivedB-2
E         ?                ^
E         + FixtureReceivedA-2
E         ? 

虽然这样做有效，但当你有很多固定装置时可能会出现问题，因为你必须自己列出所有不同的组合，而且依赖顺序也会让人困惑

您可以改为使用stack the parametrized tests，它将获得所有参数组合：

@pytest.fixture
def getDataA(request):
    return request.param.replace('ThisWillBePassedTo', 'FixtureReceived')

@pytest.fixture
def getDataB(request):
    return request.param.replace('ThisWillBePassedTo', 'FixtureReceived')

@pytest.mark.parametrize(
    'getDataB',
    [
        'ThisWillBePassedToB-1',
        'ThisWillBePassedToB-2',
        'ThisWillBePassedToB-3',
    ],
    indirect=True,
)
@pytest.mark.parametrize(
    'getDataA',
    [
        'ThisWillBePassedToA-1',
        'ThisWillBePassedToA-2',
        'ThisWillBePassedToA-3',
    ],
    indirect=True,
)
def test_comparedata(getDataA, getDataB):
    assert (getDataA == getDataB)

在这里，您可以简单地使用普通的indirect=True，参数值更清晰，仅用于getDataA或仅用于getDataB。参数化仍然遵循一个顺序：最里面的parametrized fixture也应该是传递给函数的最里面/第一个fixture。然后它会向外扩散

运行该命令将导致：

test.py::test_comparedata[ThisWillBePassedToA-1-ThisWillBePassedToB-1] ...
test.py::test_comparedata[ThisWillBePassedToA-1-ThisWillBePassedToB-2] ...
test.py::test_comparedata[ThisWillBePassedToA-1-ThisWillBePassedToB-3] ...
test.py::test_comparedata[ThisWillBePassedToA-2-ThisWillBePassedToB-1] ...
test.py::test_comparedata[ThisWillBePassedToA-2-ThisWillBePassedToB-2] ...
test.py::test_comparedata[ThisWillBePassedToA-2-ThisWillBePassedToB-3] ...
test.py::test_comparedata[ThisWillBePassedToA-3-ThisWillBePassedToB-1] ...
test.py::test_comparedata[ThisWillBePassedToA-3-ThisWillBePassedToB-2] ...
test.py::test_comparedata[ThisWillBePassedToA-3-ThisWillBePassedToB-3] ...

getDataA = 'FixtureReceivedA-1', getDataB = 'FixtureReceivedB-3'
>       assert (getDataA == getDataB)
E       AssertionError: assert 'FixtureReceivedA-1' == 'FixtureReceivedB-3'
E         - FixtureReceivedB-3
E         ?                ^ ^
E         + FixtureReceivedA-1
E         ?