Django how to trigger validation of a class property to raise an exception

Question

I have this function iam trying to test whether if discount amount is greater than the invoice amount then a validation error should be raised. Iam stuck in actually triggering the exception for it to be raised in the test. See below

class Invoice(models.Model):
    @property   
    def inv_amount(self):
        amount = Sum(quantity * price)
        return amount

    @property
    def discount_amount(self):
        amount = Sum(discount)
        return amount  

    def validate_amount(self):
        if self.discount_amount > self.inv_amount:
            raise ValidationError("discount amount cannot be greater")

def_test_validate_amount_greater_than_discount():
    with pytest.raises(ValidationError) as e:
       #Trigger the exception

@Patrick Artner the point is how would i test rasing an exception if i cant set the properties to a value... ignore the syntax errors — Josephat Macharia, Jun 01 '18 at 20:44
the point is your code throws other exceptions if you do not fix it. nevermind, i go and let you wait for some one to help — Patrick Artner, Jun 01 '18 at 21:04
[how-to-properly-assert-that-an-exception-gets-raised-in-pytest](https://stackoverflow.com/questions/23337471/how-to-properly-assert-that-an-exception-gets-raised-in-pytest) — Patrick Artner, Jun 01 '18 at 21:07

Manuel Ramiro Cavallo Maldonad · Answer 1 · 2018-06-01T22:45:18.760

0

To trigger the exception you simply should call i.validate_amount() (being i an Invoice object with wrong values) inside your with.

Also, you can use e to check if that one is your expected exception.

Edit (based on the comments of your question):

You can't set a property, but you can set the values quantity, price and discount to make it fail, assuming that those are part of the class Invoice

edited Jun 01 '18 at 22:45

answered Jun 01 '18 at 22:34

Manuel Ramiro Cavallo Maldonad

21
3

...Thanks..let me try – Josephat Macharia Jun 02 '18 at 06:53

Django how to trigger validation of a class property to raise an exception

1 Answers1