Verify pytest plugin installation and usage

Preconditions (2)

Step 1: Open a terminal or command prompt

Step 2: Install the pytest-cov plugin using pip with command 'pip install pytest-cov'

Step 3: Create a simple test file named test_sample.py with one passing test function

Step 4: Run pytest with the coverage plugin enabled using command 'pytest --cov=test_sample.py'

Step 5: Observe the test run and coverage report in the terminal output

✅ Expected Result: pytest-cov plugin installs successfully, pytest runs the test, and coverage report is displayed in the terminal

Automation Requirements - pytest

Assertions Needed:

Verify pytest-cov plugin is installed

Verify pytest runs the test file successfully

Verify coverage report is generated and contains coverage summary

Best Practices:

Use subprocess module to run shell commands for installation and test execution

Capture and assert output text for plugin confirmation and coverage report

Isolate test environment or use virtual environment to avoid conflicts

Automated Solution

PyTest

import subprocess
import sys
import re
import pytest

def test_pytest_cov_plugin_installation_and_usage():
    # Step 1: Install pytest-cov plugin
    install_result = subprocess.run([sys.executable, '-m', 'pip', 'install', 'pytest-cov'], capture_output=True, text=True)
    assert install_result.returncode == 0, f"Failed to install pytest-cov: {install_result.stderr}"

    # Step 2: Create a simple test file
    test_code = '''def test_always_passes():
    assert True
'''
    with open('test_sample.py', 'w') as f:
        f.write(test_code)

    # Step 3: Run pytest with coverage
    run_result = subprocess.run([sys.executable, '-m', 'pytest', '--cov=test_sample.py', 'test_sample.py'], capture_output=True, text=True)
    output = run_result.stdout + run_result.stderr

    # Step 4: Assertions
    # Check pytest-cov plugin is mentioned in output
    assert 'pytest-cov' in output or 'coverage' in output, "pytest-cov plugin output not found"
    # Check tests passed
    assert '1 passed' in output, "Test did not pass as expected"
    # Check coverage report summary presence
    coverage_pattern = re.compile(r'TOTAL\s+\d+\s+\d+\s+\d+%')
    assert coverage_pattern.search(output), "Coverage summary not found in output"

    # Cleanup test file
    import os
    os.remove('test_sample.py')

if __name__ == '__main__':
    pytest.main([__file__])

This test script automates the manual test case steps.

First, it installs the pytest-cov plugin using pip via subprocess.run. It asserts the installation succeeded by checking the return code.

Next, it creates a simple test file test_sample.py with one passing test function.

Then, it runs pytest with coverage enabled on that test file, capturing the output.

Assertions check that the plugin output is present, the test passed, and the coverage summary is shown.

Finally, it cleans up the test file to keep the environment clean.

This approach uses subprocess calls to simulate real user commands and verifies outputs, following best practices for plugin management testing.

Common Mistakes - 4 Pitfalls

Not checking the return code of the pip install command

Hardcoding absolute file paths for test files

Not cleaning up test files after the test run

Assuming plugin output text without verifying actual output

Bonus Challenge

Now add data-driven testing to verify installation and usage of three different pytest plugins: pytest-cov, pytest-mock, and pytest-html.

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