Day 6: GitHub Copilot Training – Debugging & Refactoring

🟦 Day 6: Debugging and Refactoring with Copilot

🎯 Goal:

Learn how to use Copilot to help:

• Fix bugs
• Improve slow or messy code
• Refactor long functions into clean parts

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🧠 What Copilot Can Do Today:

✅ Suggest fixes for errors ✅ Rewrite old code in a better way ✅ Add comments and structure ✅ Offer unit tests (with Copilot Labs)

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🔧 Step 1: Use Copilot to Fix Code

Paste this buggy code and let Copilot help fix it:

❌ Buggy Python:

def divide_numbers(a, b):
    return a / b

print(divide_numbers(5, 0))

➡ Prompt Copilot:

# Fix divide by zero error

✅ Suggests:

def divide_numbers(a, b):
    if b == 0:
        return "Cannot divide by zero"
    return a / b

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🔧 Step 2: Refactor Long Functions

Paste this:

# Calculate total price including tax and discount
def calculate(price, tax, discount):
    total = price + (price * tax)
    total = total - (total * discount)
    return total

➡ Prompt:

# Break this into smaller helper functions

Copilot may split logic like:

def apply_tax(price, tax):
    return price + (price * tax)

def apply_discount(price, discount):
    return price - (price * discount)

def calculate(price, tax, discount):
    taxed = apply_tax(price, tax)
    return apply_discount(taxed, discount)

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🔧 Step 3: Let Copilot Suggest Test Cases

Prompt:

# Write unit tests for calculate() using unittest

Copilot suggests:

import unittest

class TestCalculate(unittest.TestCase):
    def test_price_with_tax_and_discount(self):
        self.assertAlmostEqual(calculate(100, 0.1, 0.2), 88.0)

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🧪 Suggested Practice Tasks

Paste the following and let Copilot help fix or improve:

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🔹 Fix the logic

# Check if a number is prime
def is_prime(n):
    for i in range(2, n):
        if n % i == 0:
            return False
    return True

Prompt: # Fix for edge cases like n=1

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🔹 Refactor this messy JS code

function greet(user) {
  if (user != null && user.name != null && user.name !== '') {
    console.log("Hello " + user.name);
  } else {
    console.log("Hello Guest");
  }
}

Prompt: // Refactor using optional chaining and cleaner logic

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✅ Summary of Day 6

What You Did	How Copilot Helped
Fixed buggy code	Added conditions and error handling
Refactored long logic	Split into helper functions
Added test cases	Suggested unittest or describe() tests