Given-When-Then pattern in PyTest - Build an Automation Script

Verify addition of two numbers using Given-When-Then pattern

Preconditions (2)

Step 1: Given two numbers 3 and 5

Step 2: When they are added

Step 3: Then the result should be 8

✅ Expected Result: The test passes confirming the sum is correct

Automation Requirements - pytest

Assertions Needed:

Assert the sum of the two numbers equals 8

Best Practices:

Use clear Given-When-Then comments or structure in the test

Keep test simple and readable

Use assert statements for verification

Automated Solution

PyTest

import pytest

# Test function following Given-When-Then pattern
def test_add_two_numbers():
    # Given two numbers
    num1 = 3
    num2 = 5

    # When they are added
    result = num1 + num2

    # Then the result should be 8
    assert result == 8, f"Expected sum to be 8 but got {result}"

This test uses the Given-When-Then pattern to organize the steps clearly.

Given: We set two numbers num1 and num2.

When: We perform the addition operation.

Then: We assert the result equals 8 using assert. This makes the test easy to read and understand.

Common Mistakes - 3 Pitfalls

Not separating Given, When, Then steps clearly

Using print statements instead of assert for verification

Hardcoding expected result without explanation

Bonus Challenge

Now add data-driven testing with 3 different pairs of numbers and their expected sums

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