Test-Driven Development

TDD stands for Test-Driven Development — it’s a software development practice where you write tests before writing the actual code.

Here’s how it works, step by step (often called the Red–Green–Refactor cycle):

1. 🟥 Red – Write a test that defines a small piece of functionality you want.
   • The test will fail at first because the feature doesn’t exist yet.
2. 🟩 Green – Write the minimal amount of code necessary to make that test pass.
   • Focus only on making the test succeed, not on optimization or structure.
3. 🟦 Refactor – Clean up the code and tests.
   • Improve readability, remove duplication, and make sure all tests still pass.

Then you repeat the cycle for the next small piece of functionality.

Example (in Python)

# Step 1: Write a failing test
def test_addition():
    assert add(2, 3) == 5

# Step 2: Implement the code to pass the test
def add(a, b):
    return a + b

# Step 1: Write a failing test
def test_addition():
    assert add(2, 3) == 5

# Step 2: Implement the code to pass the test
def add(a, b):
    return a + b

Benefits of TDD

• Ensures your code is well-tested from the start.
• Helps prevent bugs and regressions.
• Encourages modular, maintainable code.
• Gives confidence to refactor without fear of breaking things.