Testing Workflow with pytest, Fixtures, and Coverage

Intermediate15 minTrending

Write and run Python tests with pytest, using fixtures for setup, parametrize for data-driven tests, and coverage for reporting.

Prerequisites

-Python 3.8+ installed
-A Python project with virtual environment

Steps

Install pytest and coverage

Install the pytest framework, coverage plugin for code coverage reports, and xdist for parallel test execution.

$ pip install pytest pytest-cov pytest-xdist

pytest-xdist lets you run tests in parallel with -n auto, dramatically reducing test suite times on multi-core machines.

Write and run a basic test

Run all tests in the tests/ directory with verbose output showing each test name and result. pytest auto-discovers files matching test_*.py or *_test.py.

$ pytest tests/ -v

Run tests matching a keyword

Run only tests whose names match the given keyword expression. Useful for running a subset of tests during development.

$ pytest -k 'test_login or test_signup' -v

Run tests with coverage report

Run the full test suite and generate a coverage report showing which lines in the src/ directory are not covered by tests.

$ pytest --cov=src --cov-report=term-missing tests/

Add --cov-fail-under=80 to fail the test run if coverage drops below 80 percent.

Run tests in parallel

Execute tests across all available CPU cores using pytest-xdist. This can cut test runtime by 50-80 percent on large suites.

$ pytest -n auto tests/

Parallel tests must be independent. Tests that share global state, databases, or files may fail or produce flaky results when parallelized.

Run only failed tests from the last run

Re-run only the tests that failed in the previous execution. This is the fastest way to iterate on fixing broken tests.

$ pytest --lf -v

Full Script

full-script.sh

#!/bin/bash
# Pytest testing workflow
set -e

pip install pytest pytest-cov pytest-xdist

# Create a sample test file if none exists
mkdir -p tests
cat > tests/test_example.py << 'PYEOF'
import pytest

def add(a, b):
    return a + b

class TestAdd:
    def test_integers(self):
        assert add(1, 2) == 3

    def test_strings(self):
        assert add("hello ", "world") == "hello world"

    @pytest.mark.parametrize("a,b,expected", [
        (0, 0, 0),
        (-1, 1, 0),
        (100, 200, 300),
    ])
    def test_parametrized(self, a, b, expected):
        assert add(a, b) == expected

@pytest.fixture
def sample_data():
    return {"users": ["alice", "bob"], "count": 2}

def test_with_fixture(sample_data):
    assert len(sample_data["users"]) == sample_data["count"]
PYEOF

pytest tests/ -v --tb=short
pytest tests/ --cov=tests --cov-report=term-missing

echo "All tests passed with coverage report."

FAQ

Discussion

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#!/bin/bash # Pytest testing workflow set -e pip install pytest pytest-cov pytest-xdist # Create a sample test file if none exists mkdir -p tests cat > tests/test_example.py << 'PYEOF' import pytest def add(a, b): return a + b class TestAdd: def test_integers(self): assert add(1, 2) == 3 def test_strings(self): assert add("hello ", "world") == "hello world" @pytest.mark.parametrize("a,b,expected", [ (0, 0, 0), (-1, 1, 0), (100, 200, 300), ]) def test_parametrized(self, a, b, expected): assert add(a, b) == expected @pytest.fixture def sample_data(): return {"users": ["alice", "bob"], "count": 2} def test_with_fixture(sample_data): assert len(sample_data["users"]) == sample_data["count"] PYEOF pytest tests/ -v --tb=short pytest tests/ --cov=tests --cov-report=term-missing echo "All tests passed with coverage report."