Parametrized params listed in reverse order in failed tests output

[BeforeFlight]

• a detailed description of the bug or suggestion
• output of pip list from the virtual environment you are using
• pytest and operating system versions
• minimal example if possible

Consider following test:

def my_func(use_x, use_y, use_z):
    return 1


class Tests:
    @pytest.mark.parametrize("use_x", [0, 1, 2])
    @pytest.mark.parametrize("use_y", [0, 1, 2])
    @pytest.mark.parametrize("use_z", [0, 1, 2])
    def test_test_f(self, use_x, use_y, use_z):
        print("use_x =", use_x, "use_y =", use_y, "use_z =", use_z)
        assert my_func(use_x, use_y, use_z) != 1

Output of one of the failed tests (for others situation is similar):

――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――― Tests.test_test_f[2-1-0] ―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――
../../Coding/Python/TEST/tests.py:51: in test_test_f

    assert my_func(use_x, use_y, use_z) != 1
E   assert 1 != 1
E    +  where 1 = my_func(0, 1, 2)
------------------------------------------------------------------------------------- Captured stdout call -------------------------------------------------------------------------------------
use_x = 0 use_y = 1 use_z = 2

Problem (or rather inconvenience) is that in the head of the output params are listed in reverse order. Compare:

――― Tests.test_test_f[2-1-0] ―――

use_x = 0 use_y = 1 use_z = 2

Without using print and with more parametrized params it begins really uncomfortable to debug fails.

pytest 4.6.4
OS Ubuntu 19.04

[RonnyPfannschmidt]

Parameterization with the decorator, happens in decorator application orders, which is reverse of the declaration order

I recon, that without indicative id's, this is a ux nightmare, but it's not clear yet how to change that sanely

[Zac-HD]

I recon, that without indicative id's, this is a ux nightmare, but it's not clear yet how to change that sanely

We can get the order of arguments by inspecting the test function, and order the displayed values to match their arguments.

Ultimately I think showing e.g. testname[x=1,y=2] with the argnames would be best, but matching the order would be a good start.

[RonnyPfannschmidt]

We can introduce a option to consider marks in declaration order instead of the application order

[bluetech]

@DionisiaK4 submitted a PR for this.

I am against adding an ini option for reversing decorator order:

1. Python decorators are applied from the bottom up. While it's not intuitive at first, in the long term users will be well-served by understanding this, as it's relevant beyond pytest. It is pytest after all :)
2. For someone who already understands decorator order, the reverse order is going to be confusing.
3. IMO adding a global flag which changes semantics is not a good idea. It means that at a parametrize stack you can't know the order it has without looking at the config. I think there should be one way to do it.
4. Diverging from Python semantics might possibly impede us in the future if actually want to depend on it.