# Refueling

In a file called fuel.py, reimplement Fuel Gauge from Problem Set 3, restructuring your code per the below, wherein:

• convert expects a str in X/Y format as input, wherein each of X and Y is an integer, and returns that fraction as a percentage rounded to the nearest int between 0 and 100, inclusive. If X and/or Y is not an integer, or if X is greater than Y, then convert should raise a ValueError. If Y is 0, then convert should raise a ZeroDivisionError.
• gauge expects an int and returns a str that is:
• "E" if that int is less than or equal to 1,
• "F" if that int is greater than or equal to 99,
• and "Z%" otherwise, wherein Z is that same int.
def main():
...

def convert(fraction):
...

def gauge(percentage):
...

if __name__ == "__main__":
main()


Then, in a file called test_fuel.py, implement two or more functions that collectively test your implementations of convert and gauge thoroughly, each of whose names should begin with test_ so that you can execute your tests with:

pytest test_fuel.py

Hints
• Be sure to include
import fuel


or

from fuel import convert, gauge


atop test_fuel.py so that you can call convert and gauge in your tests.

• Take care to return, not print, an int in convert and a str in gauge. Only main should call print.
• Note that you can raise an exception like ValueError with code like:
raise ValueError

• Note that you can check with pytest whether a function has raised an exception, per docs.pytest.org/en/latest/how-to/assert.html#assertions-about-expected-exceptions.

## Before You Begin

Log into cs50.dev, click on your terminal window, and execute cd by itself. You should find that your terminal window’s prompt resembles the below:

$ Next execute mkdir test_fuel  to make a folder called test_fuel in your codespace. Then execute cd test_fuel  to change directories into that folder. You should now see your terminal prompt as test_fuel/$. You can now execute

code test_fuel.py


to make a file called test_fuel.py where you’ll write your tests.

## How to Test

To test your tests, run pytest test_fuel.py. Be sure you have a copy of a fuel.py file in the same folder. Try to use correct and incorrect versions of fuel.py to determine how well your tests spot errors:

• Ensure you have a correct version of fuel.py. Run your tests by executing pytest test_fuel.py. pytest should show that all of your tests have passed.
• Modify the correct version of fuel.py, changing the return values of convert. Your program might, for example, mistakenly return a str instead of an int. Run your tests by executing pytest test_fuel.py. pytest should show that at least one of your tests has failed.
• Similarly, modify the correct version of fuel.py, changing the return values of gauge. Your program might, for example, mistakenly omit a % in the resulting str. Run your tests by executing pytest test_fuel.py. pytest should show that at least one of your tests has failed.

You can execute the below to check your tests using check50, a program CS50 will use to test your code when you submit. (Now there are tests to test your tests!). Be sure to test your tests yourself and determine which tests are needed to ensure fuel.py is checked thoroughly.

check50 cs50/problems/2022/python/tests/fuel


Green smilies mean your program has passed a test! Red frownies will indicate your program output something unexpected. Visit the URL that check50 outputs to see the input check50 handed to your program, what output it expected, and what output your program actually gave.

## How to Submit

submit50 cs50/problems/2022/python/tests/fuel