PyTest Learning

Last Updated: 2024-06-15

A hands-on learning repository for PyTest — covering basic assertions, fixtures (scopes, hooks), parameterization, markers, and Playwright integration.

Prerequisites

• Python 3.8+
• pytest — run pip install pytest
• For Playwright tests: pip install playwright then playwright install

Project Structure

PyTestLearning/
├── getting_started/          # Basic pytest concepts
│   ├── test_first.py         # Assertions, string & float comparisons
│   ├── test_second.py        # Simple assertions and prints
│   └── test_third.py         # Class-based tests
├── fixtures/                 # Pytest fixture patterns
│   ├── conftest.py           # Session-scoped db_connection fixture
│   ├── test_fixture_usage.py       # Parameter fixtures (user, page_detail)
│   ├── test_fixture_webpage.py     # Multiple fixtures per test
│   ├── test_fixture_hooks.py       # Fixture setup/teardown with yield
│   └── test_fixture_hooks_for_shared_fixture.py  # Shared fixture across modules
├── parameterize/             # @pytest.mark.parametrize patterns
│   ├── calc.py               # Simple math helper functions (add, subtract, multiply)
│   ├── test_calc.py          # Parametrized tests with ids and pytest.param()
│   └── test_playwright.py    # Nested parametrize (browser × viewport) with skip marks
├── markers/                  # Custom and built-in pytest markers
│   ├── test_markers.py       # skip, xfail, smoke, regression, slow, skipif
├── fixtures_playwright/      # Playwright + PyTest integration
│   ├── conftest.py           # Session-scoped browser & module-scoped page fixtures
│   ├── test_login.py         # Login flow (stub)
│   └── test_employeeCreation.py  # Employee creation flow (stub)
├── conftest.py               # Root: registers custom markers (smoke, regression, slow)
└── pytest.ini                # Alternative marker registration via INI (commented out)

Getting Started

Run all tests

pytest

Run a specific folder

# Getting started basics
pytest getting_started/ -v

# Fixtures
pytest fixtures/ -v

# Parameterization (new!)
pytest parameterize/ -v

# Markers (new!)
pytest markers/ -v

# Playwright integration
pytest fixtures_playwright/ -v

Run with verbose output and prints

pytest -v -s

What You'll Learn

1. Getting Started (getting_started/)

Concept	File
Basic assert statements	test_first.py, test_second.py
String assertions (in, startswith, endswith)	test_first.py
Floating-point comparison with pytest.approx()	test_first.py
Class-based test organization (class TestXxx)	test_third.py

2. Fixtures (fixtures/)

Concept	File
Module-scoped fixtures (@pytest.fixture)	test_fixture_usage.py
Multiple fixtures per test	test_fixture_webpage.py
Session-scoped fixture with setup/teardown (yield)	conftest.py + test_fixture_hooks.py
Sharing fixtures across modules via conftest.py	test_fixture_hooks_for_shared_fixture.py

Fixture scopes covered:

• Function (default) — one instance per test function
• Module — one instance per module file
• Session — one instance across the entire test run

3. Parameterization (parameterize/)

Concept	File
Basic @pytest.mark.parametrize with tuple lists	test_calc.py (test_add)
Custom test names via ids= parameter	test_calc.py (test_add_id)
Explicit pytest.param() with labeled IDs	test_calc.py (test_add_param)
Nested parametrize (cross-product of parameters)	test_playwright.py (test_login_page)
Conditional skipping with pytest.mark.skip via pytest.param()	test_playwright.py (test_login_page_param)

Key patterns:

• Basic parametrize: @pytest.mark.parametrize("a,b,expected", [...]) — passes each tuple as arguments
• Custom IDs: ids=["positive numbers", ...] — makes test output readable
• pytest.param(): pytest.param(value, id="label", marks=...) — adds labels and conditional marks (e.g., skip)
• Nested parametrize: stacking two decorators creates a cross-product of all parameter combinations

4. Markers (markers/) — new!

Concept	File
Registering custom markers via conftest.py (pytest_configure)	Root conftest.py
Registering markers via INI file (alternative)	Root pytest.ini (commented out)
@pytest.mark.skip — skip a test entirely with reason	test_markers.py (test_marker_example)
@pytest.mark.xfail — expected failure (linked to bug)	test_markers.py (test_login_feature)
Custom markers: smoke, regression, slow	test_markers.py (test_setting_user, test_setting_admin_user)
Combined markers on same test	test_markers.py (test_setting_user, test_setting_admin_user)
@pytest.mark.skipif — conditional skip based on env vars	test_markers.py (test_api_key)

Key patterns:

• Registering markers: either via conftest.py (config.addinivalue_line) or pytest.ini (INI-style)
• Built-in markers: skip, xfail, skipif — control test execution
• Custom markers: define your own (e.g., smoke, regression, slow) and run subsets with -m "smoke"
• Combined markers: stack multiple custom markers on one test (e.g., @pytest.mark.smoke + @pytest.mark.regression)
• Running subsets: pytest -m "smoke" runs only smoke tests; -m "not slow" excludes slow tests

5. Playwright Integration (fixtures_playwright/)

Demonstrates chaining fixtures with different scopes:

• browser — session-scoped, sets up once per test run
• page — module-scoped, depends on browser, sets up once per module

Test	Description
test_login.py	Login with valid credentials (stub)
test_employeeCreation.py	Employee creation flow (stub)

Key Takeaways

1. Fixtures are the backbone of reusable test setup — define them in conftest.py for automatic discovery.
2. Scope matters — choose the narrowest scope that works to keep tests fast and isolated.
3. yield in fixtures enables both setup and teardown logic (useful for DB connections, browser sessions).
4. pytest.approx() handles floating-point comparisons reliably instead of ==.
5. Class-based tests let you group related test methods under a single fixture instance (class scope).
6. @pytest.mark.parametrize runs the same test logic with multiple inputs — reduces duplication dramatically.
7. Nested parametrize creates a cross-product of all parameter combinations (e.g., 3 browsers × 3 viewports = 9 test cases).
8. pytest.param() with marks= lets you conditionally skip or mark individual parameter combinations.
9. Markers let you label, filter, and selectively run tests — register custom markers in conftest.py or pytest.ini.
10. skip, xfail, skipif — control test execution: skip entirely, expect failure (for known bugs), or conditionally skip based on environment.