How to execute python class modules along with pytest and option parser?

main
  |--> src
         |--> custom_calculation.py
         |--> test_custom_calculation.py

custom_calculation.py

def calc_total(a,b):
    return a+b

def calc_multiply(a,b):
    return a*b

test_custom_calculation.py

import custom_calculation

def test_calc_sum():
    total = custom_calculation.calc_total(10,10)
    assert total == 20

def test_calc_multiply():
    result = custom_calculation.calc_multiply(10,10)
    assert result == 100

This is how i execute for simple modules. cd main/src python -m pytest py.test -v

Learning python object oriented. Please help me if my code is wrong (could be even in importing module as well). Actual question here is, can i execute python (containing class) modules along with pytest and option parser ?

main
  |--> A
         |--> custom_calculation.py
  |--> src
         |--> test_custom_calculation.py

test_custom_calculation.py
from optparse import OptionParser
from A import *
import sys

class Test_Custom_Calculation():

    def test_calc_sum():
        total = custom_calculation.calc_total(10,10)
        assert total == 20

    def test_calc_multiply():
        result = custom_calculation.calc_multiply(10,10)
        assert result == 100

if __name__ == "__main__":
    O = Test_Custom_Calculation()

    parser = OptionParser()

    parser.add_option("-a", "--a", dest="a", default=None,
                      help="Enter value of a")

    parser.add_option("-b", "--b", dest="b", default=None,
                      help="Enter value of b")

    parser.add_option("-o", "--o", dest="o", default=None,
                      help="specify operation to be performed")

    (options, args) = parser.parse_args()

    if options.a is None or options.b is None or options.c is None:
        sys.exit("provide values of a,b and specify operation")

    if options.c == "add":
        O.test_calc_sum(a,b)
    elif options.c == "mul":
        O.test_calc_multiply(a,b)
    else:
        sys.exit("Specify appropriate operation")

without pytest, i can run this as python test_custom_calculation.py --a 10 --b 10 --c add

how can i run this with pytest ?

EDITED :

test_sample.py
def test_fun1(val1, val2, val3):

def test_fun2(val4,val5,val1):

def test_fun3(val6,val7,val8):

def test_fun4(val9,val10,val2):

def test_fun5(val2,val11,val10):

conftest.py
import pytest

def pytest_addoption(parser):

    parser.add_option("-a", "--add", dest="add", default=None,
                      help="specifies the addition operation")

    parser.add_option("-s", "--sub", dest="sub", default=None,
                      help="specifies the subtraction")

    parser.add_option("-m", "--mul", dest="mul", default=None,
                      help="specifies the multiplication")

    parser.add_option("-d", "--div", dest="div", default=None,
                      help="specifies the division")

    parser.add_option("-t", "--trigonometry", dest="trigonometry", default=None,
                      help="specifies the trigonometry operation")

where to define those functional arguments val* ?
where can we decide the logic of handling optional parser ?
    say, if option.add and option.sub:
            sys.exit("Please provide only one option")

        if option.add is None :
            sys.exit("No value provided")

        if option.add == "add":
            test_fun1(val1,val2,val3)

According to your question, i understood that you want to pass operations(add,sub) as a command line parameters, and execute the operations with the various val*.

So in Pytest, You can refer my answer:-- A way to add test specific params to each test using pytest

So it is based on test method name, logic should be handled in the fixture.