Refueling - problem set 5 - CS50

Question

I have a problem with refueling from problem set 5 of cs50p. I tried and implement a lot of version of the code, always good enough to do the job and pass the test but check50 fails. I give fuel.py and test_fuel.py, I'd be grateful if someone enligth me with the solution: fuel.py:

import sys

def main():
    percentage = None
    fraction = input("Fraction: ")
    try:
        percentage = convert(fraction)
        assert isinstance(percentage, int)

    except (ZeroDivisionError, ValueError) as e:
        pass
    except EOFError:
        sys.exit()

    if percentage != None:
        print(gauge(percentage))


def convert(fraction):
    try:
        x, y = map(int, fraction.split("/"))
        if y != 0:
            assert x < y
        percentage = round(x/y*100)
        return percentage
    except AssertionError:
        print("Error: X must be less than Y")
        raise ValueError
    except ValueError:
        print("Error: the fraction must be in the format X/Y")
        raise ValueError
    except ZeroDivisionError:
        print("Error: can't divide by 0")
        raise ZeroDivisionError


def gauge(percentage):
    if percentage <= 1:
        return "E"
    elif percentage >= 99:
        return "F"
    else:
        return f"{percentage}%"



if __name__ == "__main__":
    main()

test_fuel.py:

import random, pytest
from fuel import convert, gauge


def main():
    test_convert_0()
    test_convert_format()
    test_convert_float()
    test_convert_x_lesser_y()
    test_gauge()


def test_convert_0():
    fraction = "2/0"
    try:
        convert(fraction)
        print("Error: test did not detect ZeroDivisionError")
    except ZeroDivisionError:
        print("Test passed: ZeroDivisionError detected")
    except Exception as e:
        print(f"Error: test did not detect ZeroDivisionError, found anther error {e}")


def test_convert_format():
    fraction = "cat/dog"
    try:
        convert(fraction)
        print("Error: test did not detect ValueError")
    except ValueError:
        print("Test passed: ValueError detected")
    except Exception as e:
        print(f"Error: test did not detect ZeroDivisionError, found anther error {e}")


def test_convert_float():
    fraction = "2/3.5"
    try:
        convert(fraction)
        print("Error: test did not detect ValueError")
    except ValueError:
        print("Test passed: ValueError detected")
    except Exception as e:
        print(f"Error: test did not detect ZeroDivisionError, found anther error {e}")


def test_convert_x_lesser_y():
    fraction = "2/1"
    try:
        convert(fraction)
        print("Error: test did not detect ValueError")
    except ValueError:
        print("Test passed: ValueError detected")
    except Exception as e:
        print(f"Error: test did not detect ZeroDivisionError, found anther error {e}")


def test_gauge():
    try:
        assert gauge(random.choice([0, 1])) == "E"
    except AssertionError:
        print("Expected E, but AssertionError was raised")

    try:
        assert gauge(random.choice([99, 100])) == "F"
    except AssertionError:
        print("Expected F, but AssertionError was raised")

    try:
        n = random.choice(list(range(2, 99)))
        assert gauge(n) == f"{n}%"
    except AssertionError:
        print(f"Expected {n}%, but AssertionError was raised")

    print("Test gauge function passed")

if __name__ == "__main__":
    main()

Answer 1

You don't have any assert statements in the 1st four functions. Next, you need to modify your tests for raised exceptions. DON'T use try:/except:. Instead use with pytest.raises(exception-type):, like this:

def test_convert_ystr():
    with pytest.raises(ValueError):
        convert('3/Ken')

Finally, remove all the extraneous print statements. test_fuel.py is intended to be run with pytest, not as a python script.

Make those changes and your code should pass check50.