pytest Cheat Sheet

Updated 2026-04-29

pytest is Python's leading testing framework, built on plain assert statements with automatic introspection that shows exactly what failed and why. Unlike unittest's verbose class-based approach, pytest uses fixture dependency injection for clean test setup and a rich plugin ecosystem with 900+ extensions. The framework's key innovation is making the common case trivial—write def test_something(): assert result == expected—while providing advanced features like parametrization, markers, subtests, and parallel execution when complexity demands them. With pytest 9.0 (released 2025), the framework gained native subtests support, a new pytest.toml config file, and a comprehensive strict mode.

What This Cheat Sheet Covers

This topic spans 21 focused tables and 180 indexed concepts. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.

Table 1: Core pytest ConceptsTable 2: Assertions and ComparisonsTable 3: Fixtures - Setup and TeardownTable 4: conftest.py and Fixture SharingTable 5: ParametrizationTable 6: MarkersTable 7: Built-in FixturesTable 8: Monkeypatch OperationsTable 9: Test Discovery and CollectionTable 10: Output and ReportingTable 11: Configuration FilesTable 12: Configuration OptionsTable 13: Coverage with pytest-covTable 14: Popular pytest PluginsTable 15: Parallel Execution (pytest-xdist)Table 16: Warnings ManagementTable 17: Subtests (pytest 9.0)Table 18: Hooks and PluginsTable 19: Doctest IntegrationTable 20: Testing StrategiesTable 21: Advanced Fixture Patterns

Table 1: Core pytest Concepts

Concept	Example	Description
test function	`def test_addition():` `assert 1 + 1 == 2`	• Test functions must start with `test_` • automatic discovery finds and executes them • no classes or inheritance required.
simple assert	`assert value == 42`	• Plain Python `assert` with automatic introspection—pytest rewrites assertions to show intermediate values on failure • no special methods needed.
test file naming	`test_.py` or `_test.py`	Files must match these patterns for discovery—`test_` prefix or `_test.py` suffix trigger collection.
test class naming	`class TestUserAuth:`	• Optional classes group related tests—must start with `Test` (no `__init__`) • methods also need `test_` prefix.

Table 1: Core pytest Concepts

Concept	Example	Description
test function	`def test_addition():` `assert 1 + 1 == 2`	• Test functions must start with `test_` • automatic discovery finds and executes them • no classes or inheritance required.
simple assert	`assert value == 42`	• Plain Python `assert` with automatic introspection—pytest rewrites assertions to show intermediate values on failure • no special methods needed.
test file naming	`test_.py` or `_test.py`	Files must match these patterns for discovery—`test_` prefix or `_test.py` suffix trigger collection.
test class naming	`class TestUserAuth:`	• Optional classes group related tests—must start with `Test` (no `__init__`) • methods also need `test_` prefix.