Assertion patterns in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assert that the transaction was successful.

Blockchain / Solidity

assert transaction.status == [1]

Drag options to blanks, or click blank then click option'

AFalse

BTrue

CNone

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using False instead of True

Using 0 or None which do not represent success

The assertion checks if the transaction status is True, meaning it succeeded.

2fill in blank

medium

Complete the code to assert the balance increased by the expected amount.

Blockchain / Solidity

assert new_balance == old_balance + [1]

Drag options to blanks, or click blank then click option'

Afee

Bgas

Cnonce

Damount

Attempts:

3 left

💡 Hint

Common Mistakes

Using fee or gas which are costs, not amounts received

Using nonce which is unrelated to balance

The balance should increase by the amount transferred, not fees or other values.

3fill in blank

hard

Fix the error in the assertion that checks the event log contains the expected event.

Blockchain / Solidity

assert [1] in transaction.events

Drag options to blanks, or click blank then click option'

Aevent_log

Btransaction.event

Cexpected_event

Dtransaction.logs

Attempts:

3 left

💡 Hint

Common Mistakes

Using transaction.event which is not a valid attribute

Using event_log or transaction.logs which may not exist

The assertion must check if the expected_event is in the transaction's events list.

4fill in blank

hard

Fill both blanks to assert the smart contract's state variable equals the expected value after the call.

Blockchain / Solidity

assert contract.[1] == [2]

Drag options to blanks, or click blank then click option'

AstateVariable

BexpectedValue

CactualValue

Dbalance

Attempts:

3 left

💡 Hint

Common Mistakes

Using actualValue which is not defined

Using balance which is unrelated here

The assertion compares the contract's stateVariable to the expectedValue after execution.

5fill in blank

hard

Fill all three blanks to assert the transaction reverted with the expected error message.

Blockchain / Solidity

with pytest.raises([1]) as excinfo:
    contract.call_function()
assert [2] in str(excinfo.[3])

Drag options to blanks, or click blank then click option'

AVirtualMachineError

B"revert"

Cvalue

Dmessage

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong exception type

Checking wrong attribute of excinfo

Missing quotes around 'revert'

The code asserts that a VirtualMachineError is raised, and the error message contains "revert". The exception message is accessed via excinfo.value.