import pytest
import os
import subprocess
import sys
def write_file(filename: str, content: str):
with open(filename, 'w') as f:
f.write(content)
def test_pytest_discovery(tmp_path):
# Create test_sample.py with two test functions
test_sample_content = '''
def test_addition():
assert 1 + 1 == 2
def test_subtraction():
assert 2 - 1 == 1
'''
write_file(tmp_path / 'test_sample.py', test_sample_content)
# Create sample_test.py with one test function
sample_test_content = '''
def test_multiplication():
assert 2 * 3 == 6
'''
write_file(tmp_path / 'sample_test.py', sample_test_content)
# Create sample.py with a function named test_division (not a test file)
sample_content = '''
def test_division():
assert 6 / 2 == 3
'''
write_file(tmp_path / 'sample.py', sample_content)
# Run pytest in the tmp_path directory
result = subprocess.run(
[sys.executable, '-m', 'pytest', '--collect-only', '-q'],
cwd=tmp_path,
capture_output=True,
text=True
)
# The output lists collected tests by their node ids
collected_tests = result.stdout.strip().split('\n')
# We expect exactly 3 tests collected
assert len(collected_tests) == 3, f"Expected 3 tests collected, got {len(collected_tests)}"
# Check that the collected tests are the expected ones
expected_tests = {
'test_sample.py::test_addition',
'test_sample.py::test_subtraction',
'sample_test.py::test_multiplication'
}
assert set(collected_tests) == expected_tests, f"Collected tests do not match expected. Got: {collected_tests}"
# Run pytest normally and capture output
run_result = subprocess.run(
[sys.executable, '-m', 'pytest', '-q', '--tb=no'],
cwd=tmp_path,
capture_output=True,
text=True
)
# Check that the output contains the names of the three tests run
for test_name in ['test_addition', 'test_subtraction', 'test_multiplication']:
assert test_name in run_result.stdout, f"{test_name} not found in pytest output"
# Check that test_division is not run
assert 'test_division' not in run_result.stdout, "test_division should not be run because file name does not match discovery rules"This test script uses pytest and Python's subprocess module to verify pytest's test discovery rules.
First, it creates three Python files in a temporary directory:
test_sample.py with two test functions.sample_test.py with one test function.sample.py with a function named like a test but in a non-test file.
Then, it runs pytest --collect-only to list all discovered tests and asserts that only the three functions in the correctly named test files are collected.
Next, it runs pytest normally to execute the tests and checks the output to confirm the expected tests ran and the function in sample.py did not run.
This approach ensures the test discovery rules are correctly followed by pytest.
