A Quick Guide to Pytest

A Quick Guide to Pytest for New Team Members

Recently, while onboarding a new team member, I realized we were missing documentation on pytest. So in this post, I will share with you the onboarding pytest document used on my team, in case you need the same.

1. Writing Your First Test: Basic Payment Functionality

Let’s start with a function that processes payments.

# payment_gateway.py
def process_payment(amount, currency):
    if amount <= 0:
        raise ZeroDivisionError("Amount must be greater than zero.")
    if currency not in ["USD", "EUR", "GBP"]:
        raise ValueError("Unsupported currency.")
    return {"status": "success", "amount": amount, "currency": currency}

We’ll create our first test to verify the successful processing of a payment.

# run_tests.py
from payment_gateway import process_payment

def test_process_payment_success():
    result = process_payment(100, "USD")
    assert result == {"status": "success", "amount": 100, "currency": "USD"}

# Run the test

# collected 1 item
# run_tests.py .                                                                                                                                # [100%] 
# ====== 1 passed in 0.14s =====

So what if we want to test more scenarios? For other currencies and amounts — let’s use parameterized tests.

2. Parameterized: Add more use…