Resolving "Error Reading Historical Timing Data" in CircleCI

Overview

Encountering the error message "There was an error reading historical timing data: file does not exist" in CircleCI can be perplexing. This issue arises when attempting to use timing-based test splitting with a job configured to run with a single parallelism container. CircleCI requires more than one parallelism container to retrieve and utilize historical timing data for test splitting.

Prerequisites

• Access to the .circleci/config.yml file in your project repository.
• Familiarity with CircleCI configuration and job settings.

Solution

To resolve the error and enable timing-based test splitting, ensure that your job is configured with a parallelism value greater than 1. Follow these steps:

1. Edit the Configuration File: Open the .circleci/config.yml file in your project repository.
2. Locate the Job Configuration: Find the job where you want to enable timing-based test splitting. For example, if your job is named uk_test_features, locate its configuration.
3. Set Parallelism: Ensure the parallelism value is greater than 1. This allows CircleCI to split tests based on historical timing data. Example configuration: yaml jobs: uk_test_features: parallelism: 4 # Must be > 1 for timing-based test splitting steps: # ...
4. Save and Commit Changes: After updating the configuration, save the file and commit the changes to your repository.
5. Rerun the Workflow: Trigger the workflow again to verify that the error is resolved and timing-based test splitting is functioning as expected.

Additional Resources

• CircleCI Configuration Reference
• Optimizing Test Splitting with CircleCI

By ensuring your job's parallelism is set correctly, you can effectively utilize CircleCI's timing-based test splitting feature and avoid the historical timing data error.