Resolving "fatal: reference is not a tree" Error and Inconsistent Test Failures in CircleCI

Overview

Encountering the "fatal: reference is not a tree" error in CircleCI can be perplexing, especially when coupled with inconsistent test failures. This error typically arises when Git cannot find the commit SHA reference, often due to a deleted commit or a force push that altered the branch history. Additionally, inconsistent test failures, particularly with Selenium, may occur due to browser crashes during test runs.

Prerequisites

• Ensure you have access to modify your CircleCI configuration.
• Familiarity with Git and your version control system (VCS).

Solution

Resolving the "fatal: reference is not a tree" Error

1. Add a Delay in CI Configuration:
   • Introduce a delay or wait command in your CircleCI configuration to allow your VCS time to create the commit SHA before the CI system attempts to check it out. This can prevent the error from occurring if the job starts too quickly.

Addressing Inconsistent Test Failures

1. Increase Logging Level:

   • Enhance the logging level in your Selenium configuration to debug. This provides detailed logs that can help identify the root cause of the test failures. ruby Selenium::WebDriver.logger.level = :debug
   • Refer to the Selenium Logging Documentation for more information.

2. Implement xvfb-run:

   • If using a browser convenience image, add xvfb-run -a to your bundle exec rspec command. This can help resolve issues with the browser not starting correctly. bash xvfb-run -a bundle exec rspec

By following these steps, you can address the "fatal: reference is not a tree" error and improve the consistency of your test results in CircleCI.

Additional Resources

• CircleCI Docker Executor Infrastructure Upgrade
• Forum Discussion on xvfb Issues