I think you should check the definition of a proper fraction again and see if your test case for negative numbers is correct expecially -3/8. I will advise you to use Match.abs()

Thanks for the feedback! My implementation checks whether the value of the fraction is between 0 and 1, which is the standard mathematical definition of a proper fraction. Based on that definition:

-3/8 → -0.375 → not proper

-8/-3 → 2.66… → not proper

-3/-8 → 0.375 → proper

Using Math.abs() would treat negative fractions like -3/8 as proper, even though their value is negative. That’s why I didn’t use Math.abs(), and why my tests reflect the “between 0 and 1” definition. Happy to adjust if a different definition is expected.

The first rule of a proper fraction is that the numerator is less than the denominator. Your solution will fail on most negative numbers. Reason why a proper fraction is when the absolute value of the numerator is less than the absolute value of the denominator. A proper fraction is always less than 1

Based on your code, let's consider the following examples
you are returning properFraction > 0 && properFraction < 1

-1/2 will return false because the division is -0.5, and it is not greater than 0. But this is wrong as the result is less than 1 and the first rule of numerator < denominator stands.

Same thing with -3/8.

You can check this for further info https://www.splashlearn.com/math-vocabulary/proper-fraction

Math.abs() helps you work with negative numbers.

You can do more research on it.

Thanks for explaining! I understand now that you're using the definition based on absolute values. I’ll update my code and tests to use Math.abs() so it matches that approach.

This is good. To take it further, add a test to see if the returned error message is what you are expecting.

Thank you for the feedback . Would add further test to see what error messages they return.