Test the monkey patch thoroughly

Oct 13, 2025 by leolavanderia.com.br 132 views

Reap Invalid Session: A Solution for End-to-End Testing with Capybara and Rails

When it comes to end-to-end testing with Capybara and Rails, we often encounter situations where our tests cause the browser to crash on the Continuous Integration (CI) environment. This can be due to various reasons such as limited resources, which makes it challenging to increase the memory size on the CI environment. In such cases, we need to find a safe way to reopen the browser and continue with our tests without any issues.

If a test crashes the browser, all subsequent retry or run other tests will fail. This is because the browser session becomes invalid, and any attempt to access it will result in an error. In a CI environment, this can lead to a cascade of failures, making it difficult to diagnose and fix the issues. Therefore, it is essential to find a way to reopen the browser safely and continue with our tests.

To address this issue, we can implement a monkey patch on the Capybara#reset! method. This will allow us to remove any invalid session and start a new browser session during the next test run. The monkey patch will iterate through the session pool in reverse order, reset each session, and catch any errors that may occur. If an error occurs while resetting a session, the key of the invalid session will be added to an array, and the session will be deleted from the pool.

module Capybara
  class << self
    # MONKEY PATCH this method to reap invalid session in case of browser crashed
    # This allows subsequent test run/retry success instead of throw out invalid session id
    def reset_sessions!
      # reset in reverse so sessions that started servers are reset last
      invalid_keys = []
      session_pool.reverse_each do |key, session|
        session.reset!
      rescue => e
        puts "Encounter error while resetting session with key #{key} #{e}"
        invalid_keys << key
      end
      invalid_keys.each { |k| session_pool.delete(k) }
    end
  end
end

The monkey patch provides several benefits, including:

Improved test reliability: By removing invalid sessions, we can ensure that our tests run reliably and without errors.
Reduced test failures: With the ability to reopen the browser safely, we can reduce the number of test failures and make it easier to diagnose and fix issues.
Increased test efficiency: By avoiding the need to restart the browser for each test, we can improve the overall efficiency of our test suite.

While the monkey patch provides several benefits, there are some potential issues to consider:

Performance impact: The monkey patch may have a performance impact, especially if the session pool is large. This is because we are iterating through the session pool in reverse order and resetting each session.
Error handling: The monkey patch catches any errors that occur while resetting a session, but it may not handle all possible error scenarios. We should ensure that we have adequate error handling in place to handle any unexpected errors.
Session pool management: The monkey patch assumes that the session pool is managed correctly, but we should ensure that we have a robust session pool management strategy in place to avoid any issues.

To implement the monkey patch effectively, we should follow these best practices:

Test the monkey patch thoroughly: We should test the monkey patch extensively to ensure that it works as expected and does not introduce any new issues.
Monitor performance: We should monitor the performance of the monkey patch to ensure that it does not have a significant impact on our test suite.
Review and refine: We should regularly review and refine the monkey patch to ensure that it remains effective and efficient.

In conclusion, the monkey patch provides a safe and effective way to reopen the browser and continue with our tests even if a test crashes the browser. By implementing the monkey patch, we can improve the reliability and efficiency of our test suite and reduce the number of test failures. However, we should be aware of the potential issues and follow best practices to ensure that the monkey patch works effectively and efficiently.
Reap Invalid Session: A Solution for End-to-End Testing with Capybara and Rails - Q&A

A: The main problem is that if a test crashes the browser, all subsequent retry or run other tests will fail. This is because the browser session becomes invalid, and any attempt to access it will result in an error.

A: It is difficult to increase the memory size on the CI environment because of limited resources. This makes it challenging to run tests that require a lot of memory.

A: The workaround is to implement a monkey patch on the Capybara#reset! method. This will allow us to remove any invalid session and start a new browser session during the next test run.

A: The benefit of the workaround is that it improves test reliability, reduces test failures, and increases test efficiency.

A: The potential issues with the workaround are performance impact, error handling, and session pool management.

A: We can test the monkey patch effectively by testing it thoroughly, monitoring its performance, and reviewing and refining it regularly.

A: The best practices for implementing the workaround are to test it thoroughly, monitor its performance, and review and refine it regularly.

A: The monkey patch can be used in production environments, but it should be used with caution and only when necessary.

A: We can ensure that the monkey patch works effectively and efficiently by testing it thoroughly, monitoring its performance, and reviewing and refining it regularly.

A: The common mistakes to avoid when implementing the workaround are:

Not testing the monkey patch thoroughly
Not monitoring its performance
Not reviewing and refining it regularly
Not handling errors properly
Not managing the session pool correctly

A: The workaround can be used with other testing frameworks, but it may require modifications to the monkey patch.

A: We can customize the workaround to fit our specific needs by modifying the monkey patch to suit our testing requirements.

A: The future plans for the workaround are to continue improving its performance, reliability, and efficiency, and to make it more flexible and customizable.