Add exmaple for testing context-related issues with extend suite

Author: shaigeva

examples/bank_account_3_context_games/README.md

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+# Why another bank_account example?
+This is a variation of the bank account, where it was divided to several files, so it won't be as easy to get
+the context.
+Specifically, it's for testing extend-suite, which currently doesn't know how to bring in context for things that the
+CUT uses - so we need to add the context manually.
+
+The functionality has also been greatly reduced, so we'll always get relevant tests.
+Specifically - the premium account has 3 attributes - commision size, max deposit and max balance.
+And the values of all these attributes are in the separate file - so no matter what, we'll always
+have tests that check for them and have the wrong values if we don't manually add the context.
+
+There's a top-level-functions test file and a class-test file, so we can test both.

examples/bank_account_3_context_games/__init__.py

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+from examples.bank_account_3_context_games.bank_account_3_helpers import calc_commission_rate, is_deposit_over_balance, is_more_than_max_deposit
+
+
+class BankAccount3:
+    """ Create a new bank account """
+    def __init__(self, name, is_premium_account):
+        self._name = name
+        self._is_premium_account = is_premium_account
+        self._balance = 0
+
+    def deposit(self, amount):
+        """ deposit money """
+        if amount <= 0:
+            raise IOError("deposit amount must be larger than 0")
+        
+        if is_more_than_max_deposit(self._is_premium_account, amount):
+            raise ValueError("deposit amount exceeds maximum allowed")
+        
+        if is_deposit_over_balance(self._is_premium_account, amount, self._balance):
+            raise ValueError("deposit amount will exceed maximum allowed balance")
+        
+        self._balance += amount - calc_commission_rate(self._is_premium_account)
+
+    def balance(self):
+        return self._balance

examples/bank_account_3_context_games/bank_account_3.py

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+MAX_DEPOSIT_PREMIUM = 1_000_000
+MAX_DEPOSIT_NON_PREMIUM = 10_000
+
+MAX_BALANCE_PREMIUM = 10_000_000
+MAX_BALANCE_NON_PREMIUM = 100_000
+
+def calc_commission_rate(is_premium_account):
+    if is_premium_account:
+        return 1.5
+    else:
+        return 8
+
+
+def is_more_than_max_deposit(is_premium_account, deposit_amount):
+    if is_premium_account:
+        return deposit_amount > MAX_DEPOSIT_PREMIUM
+    else:
+        return deposit_amount > MAX_DEPOSIT_NON_PREMIUM
+
+
+def is_deposit_over_balance(is_premium_account, deposit_amount, balance):
+    expected_balance = balance + deposit_amount - calc_commission_rate(is_premium_account)
+
+    if is_premium_account:
+        return expected_balance > MAX_BALANCE_PREMIUM
+    else:
+        return expected_balance > MAX_BALANCE_NON_PREMIUM

examples/bank_account_3_context_games/bank_account_3_helpers.py

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+import pytest
+from examples.bank_account_3_context_games.bank_account_3 import BankAccount3
+
+
+class TestBankAccountSimpson:
+    def setup_method(self):
+        self.homer = BankAccount3("Homer", True)
+        self.marge = BankAccount3("Marge", False)
+    
+    def test_deposit_with_commission_discount_true(self):
+        initial_balance = self.homer.balance()
+        deposit_amount = 100
+        expected_commission = 1.5
+        expected_balance = initial_balance + deposit_amount - expected_commission
+        
+        self.homer.deposit(deposit_amount)
+
+        assert self.homer.balance() == expected_balance

examples/bank_account_3_context_games/test_bank_account_3.py

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+from examples.bank_account_3_context_games.bank_account_3 import BankAccount3
+
+def test_deposit_with_premium_account_true():
+    homer = BankAccount3("Homer", True)
+    initial_balance = homer.balance()
+    deposit_amount = 100
+    expected_commission = 1.5
+    expected_balance = initial_balance + deposit_amount - expected_commission
+    
+    homer.deposit(deposit_amount)
+
+    assert homer.balance() == expected_balance