Why testing prevents costly bugs in Blockchain / Solidity - See It in Action

Why Testing Prevents Costly Bugs in Blockchain

📖 Scenario: Imagine you are building a simple blockchain smart contract simulation. Bugs in blockchain code can cause huge financial losses. Testing your code carefully helps catch mistakes early, saving money and trust.

🎯 Goal: You will create a small blockchain transaction record, set a limit for valid transactions, filter out invalid ones using a comprehension, and print the valid transactions. This shows how testing and filtering prevent costly errors.

📋 What You'll Learn

Create a dictionary called transactions with exact entries for 5 users and their transaction amounts

Create a variable called max_amount set to 1000

Use a dictionary comprehension called valid_transactions to keep only transactions less than or equal to max_amount

Print the valid_transactions dictionary

💡 Why This Matters

🌍 Real World

In blockchain development, testing transaction limits prevents sending or accepting invalid amounts that could cause financial loss.

💼 Career

Blockchain developers must write safe, tested code to avoid costly bugs that can damage reputation and cause legal issues.

1

DATA SETUP: Create the transactions dictionary

Create a dictionary called transactions with these exact entries: 'Alice': 500, 'Bob': 1500, 'Charlie': 700, 'Diana': 1200, 'Eve': 300

Blockchain / Solidity

# Create the transactions dictionary with exact entries
# Your code here

Need a hint?

Use curly braces {} to create a dictionary with the exact keys and values.

2

CONFIGURATION: Set the maximum allowed transaction amount

Create a variable called max_amount and set it to 1000

Blockchain / Solidity

transactions = {'Alice': 500, 'Bob': 1500, 'Charlie': 700, 'Diana': 1200, 'Eve': 300}
# Set max_amount to 1000
# Your code here

Need a hint?

Just assign 1000 to the variable max_amount.

3

CORE LOGIC: Filter valid transactions using dictionary comprehension

Create a dictionary comprehension called valid_transactions that includes only entries from transactions where the amount is less than or equal to max_amount

Blockchain / Solidity

transactions = {'Alice': 500, 'Bob': 1500, 'Charlie': 700, 'Diana': 1200, 'Eve': 300}
max_amount = 1000
# Create valid_transactions dictionary comprehension
# Your code here

Need a hint?

Use {key: value for key, value in dict.items() if condition} format.

4

OUTPUT: Print the valid transactions

Write a print statement to display the valid_transactions dictionary

Blockchain / Solidity

transactions = {'Alice': 500, 'Bob': 1500, 'Charlie': 700, 'Diana': 1200, 'Eve': 300}
max_amount = 1000
valid_transactions = {user: amount for user, amount in transactions.items() if amount <= max_amount}
# Print the valid_transactions dictionary
# Your code here

Need a hint?

Use print(valid_transactions) to show the filtered dictionary.