Assertion error testing attributes and methods in a class-CodePudding

For the sake of practice, I am writing a class BankAccount to learn OOP in python. In an attempt to make my program more redundant am trying to write a test function test_BankBankAccount() to practice how to do test functions as well.

The test function test_BankBankAccount() is suppose to test that the methods deposit(), withdraw(), transfer() and get_balance() work as intended.

However, the test function fails because the methods inside of the computed_deposit = test_account.deposit(400), computed_transfer = test_account.transfer(test_account2, 200) and so on doesn't seem to store the values i asign to them.

**This is the error message I receive (which is the exact one i try to avoid) **

assert success1 and success2 and success3 and success4, (msg1, msg2, msg3, msg4)
AssertionError: ('computet deposit = None is not 400', 'computet transfer = None is not 200', 'computet withdrawal = None is not 200', 'computet balance = 0 is not 0')

Here is a snippet of much of the code I have written so far

class BankAccount:
    def __init__(self, first_name, last_name, number, balance):
        self._first_name = first_name
        self._last_name = last_name
        self._number = number
        self._balance = balance

    def deposit(self, amount):
        self._balance  = amount

    def withdraw(self, amount):
        self._balance -= amount

    def get_balance(self):
        return self._balance

    def transfer(self,other_account, transfer_amount):
        self.withdraw(transfer_amount)
        other_account.deposit(transfer_amount)                  

    def print_info(self):
        first = self._first_name
        last = self._last_name
        number = self._number
        balance = self._balance

        s = f"{first} {last}, {number}, balance: {balance}"

        print(s)

def main():

    def test_BankBankAccount():
        test_account = BankAccount("Dude", "man", "1234", 0)
        test_account2 = BankAccount("Dude2", "man2","5678", 0)

        expected_deposit = 400
        expected_withdrawal = 200
        expected_transfer = 200
        expected_get_balance = 0

        computed_deposit = test_account.deposit(400)
        computed_transfer = test_account.transfer(test_account2, 200)
        computed_withdrawal = test_account.withdraw(200)
        computed_get_balance = test_account.get_balance()

        #tol = 1E-17

        success1 = abs(expected_deposit == computed_deposit) #< tol
        success2 = abs(expected_transfer == computed_transfer) #< tol
        success3 = abs(expected_withdrawal == computed_withdrawal) #< tol
        success4 = abs(expected_get_balance == computed_get_balance)  #<tol

        msg1 = f"computet deposit = {computed_deposit} is not {expected_deposit}"
        msg2 = f"computet transfer = {computed_transfer} is not {expected_transfer}"
        msg3 = f"computet withdrawal = {computed_withdrawal} is not {expected_withdrawal}"
        msg4 = f"computet balance = {computed_get_balance} is not {expected_get_balance}"
        assert success1 and success2 and success3 and success4, (msg1, msg2, msg3, msg4)

    test_BankBankAccount()

My question is:

Is there anyone who is kind enough to help me fix this and spot my mistakes?

All help is welcomed and appreciated.

CodePudding user response：

The problem is that you are not returning anything from some of these member functions.

Try, for example, making deposit look like this:

def deposit(self, amount):
    self._balance  = amount
    return self._balance

CodePudding user response：

As an alternative to Goodword's answer, you might try:

        test_account.deposit(400)
        computed_deposit = test_account.get_balance()
        
        test_account.transfer(test_account2, 200)
        computed_withdrawal = test_account.get_balance()
        computed_transfer = test_account2.get_balance()

        test_account.withdraw(200)
        computed_get_balance = test_account.get_balance()

Regarding testing, hats off to you! I'd recommend familiarising yourself with Python's unittesting framework, as it will serve you well in the long run.

For example, you might define a class for testing your BankAccount, such as

import unittest
class TestBankAccount(unittest.TestCase):
    # setUp gets run before every individual test
    def setUp(self):
        self.account1 = BankAccount("First","Account","1234",0)
        self.account2 = BankAccount("Second","Account","5678",200)

    def test_deposit(self):
        self.account1.deposit(400)
        self.assertEqual(self.account1.get_balance(),400)

    def test_withdraw(self):
        self.account2.withdraw(200)
        self.assertEqual(self.account1.get_balance(),0)

    def test_transfer(self):
        self.account2.transfer(self.account1,200)
        self.assertEqual(self.account1.get_balance(),200)
        self.assertEqual(self.account2.get_balance(),0)

if __name__=="__main__":
    unittest.main()