Running Tests - CLI Options

Basic Test Execution

The simplest way to run tests is to execute pytest in your project directory:

pytest

This discovers and runs all tests in the current directory and subdirectories.

Running Specific Files

You can target a specific test file:

pytest tests/test_login.py

Or run a specific test function within a file:

pytest tests/test_login.py::test_valid_login

Useful CLI Flags

pytest offers many command-line options to control test execution:

# Verbose output - show each test name
pytest -v

# Stop after first failure
pytest -x

# Run last failed tests only
pytest --lf

# Show print output (capture off)
pytest -s

# Run tests in parallel (requires pytest-xdist)
pytest -n auto

# Show the N most recent failures
pytest --tb=short

Selecting Tests with -k

The -k flag lets you filter tests by name expression:

# Run tests whose names contain "login"
pytest -k login

# Run tests whose names do NOT contain "slow"
pytest -k "not slow"

# Combine expressions
pytest -k "login or logout"

This is useful when you want to run a subset of tests without modifying your code.

Listing Tests

To see which tests would be run without actually running them:

# List all collected tests
pytest --collect-only

# List tests matching a keyword
pytest --collect-only -k login