CU-86dtu91p0 - Include how to test smart contract storage using boa t…

…est constructor

docs/source/testing-and-debugging.md

@@ -135,3 +135,37 @@ of the transaction.
         result, _ = await self.call("get_message", return_type=str)
         self.assertEqual(new_message, result)
 ```
+
+#### Accessing the Storage
+
+To get the key-value pairs stored in the smart contract's storage, you can use the `get_storage` method from 
+`SmartContractTestCase`. Use it with the prefix of the keys you want to access, and you'll get a `dict[bytes, bytes]`.
+If you want to get a dictionary of other types, you can also pass a function as argument to process the keys or values
+before adding it to the dict. If want to remove the prefix from the result you can use the `remove_prefix` parameter.
+
+```python
+    # inside the HelloWorldWithDeployTest class
+    async def test_smart_contract_storage(self):
+        from boaconstructor.storage import as_uint160, as_int
+        from typing import cast
+
+        # this is the prefix that the GAS smart contract uses to store the accounts and their balances
+        account_prefix = b'\x14'
+
+        # the return from get_storage needs to be casted to the expected type
+        accounts = cast(
+            dict[types.UInt160, int],
+            await self.get_storage(
+                account_prefix, target_contract=GAS, remove_prefix=True,
+                # we are using the methods from `boaconstructor.storage` to return keys as UInt160 and values as int
+                key_post_processor=as_uint160, values_post_processor=as_int
+            )
+        )
+
+        self.assertIn(self.genesis.script_hash, accounts)
+        genesis_balance = accounts[self.genesis.script_hash]
+        self.assertGreater(genesis_balance, 0)
+        self.assertIn(self.user1.script_hash, accounts)
+        user1_balance = accounts[self.user1.script_hash]
+        self.assertGreater(user1_balance, 0)
+```