What will you learn?

by

In this tutorial, you’ll learn how to handle global exceptions in pytest and fail a test after it has already passed. We’ll explore the use of pytest_runtest_makereport hook to check for exceptions even after a test has successfully passed.

Introduction to the Problem and Solution

When running tests with pytest, there are situations where we need to verify global exceptions even after a test has passed. This ensures specific conditions are met and desired exceptions are not raised during testing. To address this, we can utilize pytest hooks like pytest_runtest_makereport to access test outcome information. By examining these reports, we can implement logic to validate global exceptions and mark a test as failed if needed.

Code

import pytest

def pytest_runtest_makereport(item, call):
    if call.excinfo is not None:
        # Check for any exception raised during the test execution
        raise call.excinfo.value  # Raise the exception again to fail the test

# Test function where an exception might occur
def test_example():
    assert 1 + 1 == 2  # Sample passing assertion
    # Uncomment line below to simulate an exception during testing
    # assert 1 / 0  


# Copyright PHD

Credit: PythonHelpDesk.com

Explanation

  • pytest_runtest_makereport Hook: Called when a new report object is created, providing access to executed test case information.
  • call.excinfo: Contains details about any captured exception during a specific test execution.
  • raise call.excinfo.value: Re-raising captured exceptions within this hook allows us to fail a test post successful assertions.
    How does pytest_runtest_makereport assist in checking for global exceptions?

    By using pytest_runtest_makereport, we can inspect each test’s outcome, including any captured exceptions, enabling custom logic based on these reports.

    Can I selectively choose tests for global exception checks using this method?

    Yes, conditional checks within pytest_runtest_makereport allow selective verification of specific tests based on requirements.

    Will failing a previously passed test impact subsequent tests?

    Failing one testcase won’t directly affect other subsequent tests; each runs independently unless specified otherwise.

    Is deliberately causing failures in passing tests recommended?

    Introducing deliberate failures in passing tests should be done judiciously for strict validation criteria or exceptional handling scenarios.

    How do I run only specific tests with modified failure behavior locally without affecting others?

    Mark special cases with custom markers or organize them into separate files/suites when running local testing environments.

    Conclusion

    Handling global exceptions post successful assertions offers valuable insights into application stability beyond basic pass/fail results in automated testing suites using PyTest framework. Leveraging hooks effectively ensures robust error-handling strategies enhancing software quality.

    Leave a Comment