如何使用callable作爲pytest參數ize（）參數？

Question

是否有辦法指定pytest的pytest.mark.parametrize()參數的可調用參數，以便僅在選擇運行測試時動態生成參數？

我有一些昂貴的操作要執行以生成參數，我只想執行它們，如果測試被選中運行。

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，你可以創建一個代理：

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

我想這是你想要的東西 - 昂貴的計算是燈具內部哪些僅在調用測試並且昂貴的計算僅進行一次時才被調用：

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