如何使用callable作为pytest参数ize（）参数？

Question

是否有办法指定pytest的pytest.mark.parametrize()参数的可调用参数，以便仅在选择运行测试时动态生成参数？

我有一些昂贵的操作要执行以生成参数，我只想执行它们，如果测试被选中运行。

例如，

import pytest 

def my_callable(): 
    # do expensive operations here 
    return [(1, 2), (3, 6)] 


# I want my_callable to be called only if test_something 
# has been selected to be run 
@pytest.mark.parametrize("my_parm_1,my_parm_2", my_callable) 
def test_something(my_parm_1, my_parm_2): 
    assert my_parm_1 * 2 == my_parm_2 

Answer 1

，而不是直接使用@pytest.mark.parametrizemycallable，你可以创建一个代理：

def my_callable(): 
    # do expensive operations here 
    return [(1, 2), (3, 6)] 

expensive_params = [paramset for paramset in my_callable()] 

@pytest.mark.parametrize("my_parm_1,my_parm_2", expensive_params) 
... 

Answer 2

我想这是你想要的东西 - 昂贵的计算是灯具内部哪些仅在调用测试并且昂贵的计算仅进行一次时才被调用：

class TestSomething: 

    _result = None 

    @pytest.fixture() 
    def my_callable(self): 
     if TestSomething._result is None: 
      # do expensive operations here 
      TestSomething._result = [(1, 2), (3, 6)] 

     def _my_callable(run_number): 
      return TestSomething._result[run_number] 
     return _my_callable 

    @pytest.mark.parametrize("run_number", [0, 1]) 
    def test_something(self, run_number, my_callable): 
     my_param_1, my_param_2 = my_callable(run_number) 
     assert my_param_1 * 2 == my_param_2