test getting skipped in pytest

Question

I am trying to use parametrize for which I want to give testcases which I get from a different function using pytest. I have tried this

test_input = []
rarp_input1 = ""
rarp_output1 = ""
count =1
def test_first_rarp():
    global test_input
    config = ConfigParser.ConfigParser()
    config.read(sys.argv[2])
    global rarp_input1
    global rarp_output1
    rarp_input1 = config.get('rarp', 'rarp_input1')
    rarp_input1 =dpkt.ethernet.Ethernet(rarp_input1)
    rarp_input2 = config.get('rarp','rarp_input2')
    rarp_output1 = config.getint('rarp','rarp_output1')
    rarp_output2 = config.get('rarp','rarp_output2')
    dict_input = []
    dict_input.append(rarp_input1)
    dict_output = []
    dict_output.append(rarp_output1)
    global count
    test_input.append((dict_input[0],count,dict_output[0]))
    #assert test_input == [something something,someInt]

@pytest.mark.parametrize("test_input1,test_input2,expected1",test_input)
def test_mod_rarp(test_input1,test_input2,expected1):
    global test_input
    assert mod_rarp(test_input1,test_input2) == expected1

But the second test case is getting skipped. It says

test_mod_rarp1.py::test_mod_rarp[test_input10-test_input20-expected10]

Why is the test case getting skipped? I have checked that neither the function nor the input is wrong. Because the following code is working fine

@pytest.mark.parametrize("test_input1,test_input2,expected1,[something something,someInt,someInt])
def test_mod_rarp(test_input1,test_input2,expected1):
    assert mod_rarp(test_input1,test_input2) == expected1

I have not put actual inputs here. Its correct anyway. Also I have config file from which I am taking inputs using configParser. test_mod_rarp1.py is the python file name where I am doing this. I basically want to know if we can access variables(test_input in my example) from other functions to use in parametrize if that is causing problem here. If we can't how do I change the scope of the variable?

Answer 1

Parametrization happens at compile time so that is the reason if you want to parametrized on data generated at run time it skips that.

The ideal way to acheive what you are trying to do is by using fixture parametrization.

Below example should clear things for you and then you could apply the same logic in your case

import pytest
input = []

def generate_input():
    global input
    input = [10,20,30]



@pytest.mark.parametrize("a", input)
def test_1(a):
    assert a < 25

def generate_input2():
    return [10, 20, 30]


@pytest.fixture(params=generate_input2())
def a(request):
    return request.param

def test_2(a):
    assert a < 25

OP

<SKIPPED:>pytest_suites/test_sample.py::test_1[a0]


********** test_2[10] **********
<EXECUTING:>pytest_suites/test_sample.py::test_2[10]
Collected Tests
TEST::pytest_suites/test_sample.py::test_1[a0]
TEST::pytest_suites/test_sample.py::test_2[10]
TEST::pytest_suites/test_sample.py::test_2[20]
TEST::pytest_suites/test_sample.py::test_2[30]

See test_1 was skipped because parameterization happened before execution of generate_input() but test_2 gets parameterized as required