Given-When-Then pattern in PyTest - Framework Patterns

Framework Mode - Given-When-Then pattern

Folder Structure

project-root/
├── tests/
│   ├── test_login.py
│   ├── test_checkout.py
│   └── conftest.py
├── pages/
│   ├── login_page.py
│   └── checkout_page.py
├── utils/
│   ├── helpers.py
│   └── fixtures.py
├── configs/
│   └── config.yaml
├── reports/
│   └── latest_report.html
└── pytest.ini
  

Test Framework Layers

• Test Layer: Contains test files in tests/ using Given-When-Then style for clarity.
• Page Objects Layer: In pages/, classes represent pages with methods for actions and verifications.
• Utilities Layer: Helper functions and fixtures in utils/ to support tests and setup.
• Configuration Layer: Environment and test settings in configs/ and pytest.ini.
• Reporting Layer: Test results saved in reports/ for review and CI/CD integration.

Configuration Patterns

Use pytest.ini to set default options like markers and test paths.

Store environment-specific data (URLs, credentials) in configs/config.yaml. Load this data in fixtures.

Use conftest.py to define fixtures that provide test setup, like browser drivers or test data.

Example snippet to load config in conftest.py:

import yaml
import pytest

@pytest.fixture(scope="session")
def config():
    with open("configs/config.yaml") as f:
        return yaml.safe_load(f)
  

Test Reporting and CI/CD Integration

• Use pytest built-in options like --junitxml=reports/report.xml to generate XML reports.
• Integrate with CI tools (GitHub Actions, Jenkins) to run tests on code changes and publish reports.
• Use plugins like pytest-html to create readable HTML reports saved in reports/.
• Reports help quickly see which Given-When-Then steps passed or failed.

Framework Design Principles

1. Clear Separation: Keep Given (setup), When (action), Then (assertion) steps distinct in tests for readability.
2. Reusable Fixtures: Use pytest fixtures to provide common setup (Given) to avoid repetition.
3. Page Object Model: Encapsulate page interactions to keep When steps clean and maintainable.
4. Descriptive Assertions: Write Then steps with clear assertions that explain expected outcomes.
5. Configurable Environments: Use config files and fixtures to run tests in different environments without code changes.

Self Check

Where would you add a new page object class for the "User Profile" page in this framework structure?

Key Result

Organize pytest tests using Given-When-Then steps with clear layers: tests, page objects, utilities, configs, and reports.

Practice

1. What is the main purpose of the Given-When-Then pattern in pytest tests?

easy

A. To write tests only for user interface elements

B. To organize tests into setup, action, and verification steps

C. To speed up test execution by skipping setup

D. To avoid using assertions in tests

Solution

1. Step 1: Understand the pattern roles

   Given-When-Then divides a test into three parts: Given (setup), When (action), Then (check).

2. Step 2: Match purpose with options

   Only To organize tests into setup, action, and verification steps correctly describes this organization purpose.

3. Final Answer:

   To organize tests into setup, action, and verification steps -> Option B

4. Quick Check:

   Given-When-Then = organize test steps [OK]

Hint: Remember: Given=setup, When=action, Then=check [OK]

Common Mistakes:

• Thinking it only applies to UI tests
• Believing it skips setup steps
• Assuming no assertions are used

2. Which of the following is the correct way to write a Given-When-Then style pytest test function?

easy

A. def test_example():
# Given
x = 5
# When
y = x + 3
# Then
assert y == 8

B. def test_example():
x = 5
y = x + 3
assert y == 8
# Given-When-Then comments missing

C. def test_example():
assert 5 + 3 == 8
# Given-When-Then not used

D. def test_example():
# When
x = 5
# Given
y = x + 3
# Then
assert y == 8

Solution

1. Step 1: Check comment order and code logic

   def test_example(): # Given x = 5 # When y = x + 3 # Then assert y == 8 correctly uses Given-When-Then comments in order with proper setup, action, and assertion.

2. Step 2: Identify incorrect patterns

   The other options either lack Given-When-Then comments or have them in the wrong order (e.g., When before Given).

3. Final Answer:

   def test_example():\n # Given\n x = 5\n # When\n y = x + 3\n # Then\n assert y == 8 -> Option A

4. Quick Check:

   Correct comment order = def test_example(): # Given x = 5 # When y = x + 3 # Then assert y == 8 [OK]

Hint: Follow comment order: Given, When, Then [OK]

Common Mistakes:

• Mixing the order of Given and When comments
• Skipping comments entirely
• Placing assertions outside Then step

3. Given the following pytest test using Given-When-Then pattern, what will be the test result?

def test_sum():
    # Given
    numbers = [1, 2, 3]
    # When
    total = sum(numbers)
    # Then
    assert total == 6

medium

A. Test will fail because assertion is wrong

B. Test will fail because sum is calculated incorrectly

C. Test will error due to missing import

D. Test will pass because sum of [1, 2, 3] is 6

Solution

1. Step 1: Calculate sum of list

   The sum of [1, 2, 3] is 1+2+3 = 6.

2. Step 2: Check assertion correctness

   The assertion checks total == 6, which is true, so test passes.

3. Final Answer:

   Test will pass because sum of [1, 2, 3] is 6 -> Option D

4. Quick Check:

   sum([1,2,3]) = 6 [OK]

Hint: Calculate sum and compare with assertion value [OK]

Common Mistakes:

• Assuming sum returns a list instead of number
• Thinking assertion expects a different value
• Confusing test error with failure

4. Identify the error in this Given-When-Then pytest test:

def test_multiply():
    # Given
    x = 4
    y = 5
    # When
    result = x * y
    # Then
    assert result = 20

medium

A. Syntax error in assertion statement

B. Wrong variable names used

C. Missing setup in Given step

D. No assertion in Then step

Solution

1. Step 1: Check assertion syntax

   The assertion uses single '=' which is assignment, not comparison. It should be '==' for comparison.

2. Step 2: Confirm other parts are correct

   Variables and steps are correct; only assertion syntax is wrong.

3. Final Answer:

   Syntax error in assertion statement -> Option A

4. Quick Check:

   Use '==' in assert, not '=' [OK]

Hint: Use '==' for assert comparisons, not '=' [OK]

Common Mistakes:

• Using '=' instead of '==' in assert
• Confusing assignment with comparison
• Ignoring syntax errors in assertions

5. You want to test a function that filters out falsy values (like 0, '', None) from a list using Given-When-Then pattern in pytest. Which test code correctly applies this pattern and checks the result?

hard

A. def test_filter_falsy():
# Given
data = [0, 1, '', 'hello', None, True]
# Then
assert filtered == [1, 'hello', True]
# When
filtered = [x for x in data if x]

B. def test_filter_falsy():
data = [0, 1, '', 'hello', None, True]
filtered = [x for x in data if x]
assert filtered == [1, 'hello', True]

C. def test_filter_falsy():
# Given
data = [0, 1, '', 'hello', None, True]
# When
filtered = [x for x in data if x]
# Then
assert filtered == [1, 'hello', True]

D. def test_filter_falsy():
# Given
data = [0, 1, '', 'hello', None, True]
# When
filtered = filter(lambda x: x, data)
# Then
assert list(filtered) == [0, 1, '', 'hello', None, True]

Solution

1. Step 1: Verify Given-When-Then structure

   def test_filter_falsy(): # Given data = [0, 1, '', 'hello', None, True] # When filtered = [x for x in data if x] # Then assert filtered == [1, 'hello', True] correctly uses Given for data setup, When for filtering action, Then for assertion check.

2. Step 2: Check correctness of filtering and assertion

   Filtering removes falsy values; expected list matches filtered result. Other options miss comments or have wrong assertion.

3. Final Answer:

   def test_filter_falsy():\n # Given\n data = [0, 1, '', 'hello', None, True]\n # When\n filtered = [x for x in data if x]\n # Then\n assert filtered == [1, 'hello', True] -> Option C

4. Quick Check:

   Given-When-Then + correct filter = def test_filter_falsy(): # Given data = [0, 1, '', 'hello', None, True] # When filtered = [x for x in data if x] # Then assert filtered == [1, 'hello', True] [OK]

Hint: Keep steps clear: setup, action, then check [OK]

Common Mistakes:

• Skipping Given-When-Then comments
• Asserting wrong filtered list
• Using filter object without converting to list