Python Testing 101 pytest Example: Calculator Class Tests

test_calc_class.py

import pytest
from com.automationpanda.example.calc_class import Calculator

# "Constants"

NUMBER_1 = 3.0
NUMBER_2 = 2.0


# Fixtures

@pytest.fixture
def calculator():
    return Calculator()


# Helpers

def verify_answer(expected, answer, last_answer):
    assert expected == answer
    assert expected == last_answer


# Test Cases

def test_last_answer_init(calculator):
    assert calculator.last_answer == 0.0


def test_add(calculator):
    answer = calculator.add(NUMBER_1, NUMBER_2)
    verify_answer(5.0, answer, calculator.last_answer)


def test_subtract(calculator):
    answer = calculator.subtract(NUMBER_1, NUMBER_2)
    verify_answer(1.0, answer, calculator.last_answer)


def test_subtract_negative(calculator):
    answer = calculator.subtract(NUMBER_2, NUMBER_1)
    verify_answer(-1.0, answer, calculator.last_answer)


def test_multiply(calculator):
    answer = calculator.multiply(NUMBER_1, NUMBER_2)
    verify_answer(6.0, answer, calculator.last_answer)


def test_divide(calculator):
    answer = calculator.divide(NUMBER_1, NUMBER_2)
    verify_answer(1.5, answer, calculator.last_answer)


def test_divide_by_zero(calculator):
    with pytest.raises(ZeroDivisionError) as e:
        calculator.divide(NUMBER_1, 0)
    assert "division by zero" in str(e.value)


@pytest.mark.parametrize("a,b,expected", [
    (NUMBER_1, NUMBER_2, NUMBER_1),
    (NUMBER_2, NUMBER_1, NUMBER_1),
    (NUMBER_1, NUMBER_1, NUMBER_1),
])
def test_maximum(calculator, a, b, expected):
    answer = calculator.maximum(a, b)
    verify_answer(expected, answer, calculator.last_answer)


@pytest.mark.parametrize("a,b,expected", [
    (NUMBER_1, NUMBER_2, NUMBER_2),
    (NUMBER_2, NUMBER_1, NUMBER_2),
    (NUMBER_2, NUMBER_2, NUMBER_2),
])
def test_minimum(calculator, a, b, expected):
    answer = calculator.minimum(a, b)
    verify_answer(expected, answer, calculator.last_answer)

i love you thanks very much