Rails: Fixing BacktraceCleanerCleanLocationsTest Failures

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BacktraceCleanerCleanLocationsTest Fails When Running Via bin/test

Hey everyone!

We've got an interesting issue to dive into today regarding the BacktraceCleanerCleanLocationsTest in Rails. It seems like some tests are failing when executed through the bin/test command. Let's break down the problem, understand the steps to reproduce it, and figure out what's going on under the hood. Understanding and resolving test failures is crucial for maintaining the stability and reliability of the Rails framework. This article will walk you through the specifics of the issue and potential solutions.

Steps to Reproduce

To get started, reproducing the issue is pretty straightforward. Here’s what you need to do:

  1. Clone the Rails repository: First, you'll want to clone the Rails repository from GitHub. This gives you a local copy to work with.

    git clone https://github.com/rails/rails

  2. Navigate to the activesupport directory: Change your current directory to activesupport within the Rails directory.

    cd rails/activesupport

  3. Install dependencies: Use Bundler to install all the necessary dependencies. This ensures you have all the required gems.

    bundle install

  4. Run the specific test: Execute the test that’s causing the problem using the bin/test command. Specify the test file and the test name to focus on the failing test.

    bin/test test/backtrace_cleaner_test.rb -n /test_returns_all_clean_location/

By following these steps, you should be able to reproduce the failure and see the same results we're discussing. Reproducing the error is the first step towards finding a solution.

Expected Behavior

Ideally, when you run the test, you should see all tests passing without any failures. The BacktraceCleaner is supposed to clean up backtraces, and the test should verify that it does so correctly. In a perfect scenario, every test should pass, indicating that the backtrace cleaner is functioning as expected. Specifically, the test_returns_all_clean_locations test should confirm that the cleaner returns only the expected clean locations without any unexpected entries. A successful test run confirms the reliability of the backtrace cleaning process, which is essential for debugging and error reporting in Rails applications. A clean backtrace makes it easier to identify the source of an error, speeding up the development and maintenance process. Therefore, the expected behavior is a green light across all tests, ensuring the BacktraceCleaner is doing its job correctly.

Actual Behavior

Unfortunately, the actual behavior is different from what we expect. When running the specified test, two tests fail. Here’s the output you might see:

$ bin/test test/backtrace_cleaner_test.rb -n /test_returns_all_clean_location/
Running 31 tests in a single process (parallelization threshold is 50)
Run options: -n /test_returns_all_clean_location/ --seed 12502

# Running:

.F

Failure:
BacktraceCleanerCleanLocationsTest#test_returns_all_clean_locations_(:silent) [test/backtrace_cleaner_test.rb:254]:
--- expected
+++ actual
@@ -1 +1 @@
-["/home/yahonda/src/github.com/rails/rails/activesupport/test/backtrace_cleaner_test.rb"]
+["/home/yahonda/src/github.com/rails/rails/activesupport/test/backtrace_cleaner_test.rb", "/home/yahonda/src/github.com/rails/rails/railties/lib/rails/test_unit/line_filtering.rb"]



bin/test test/backtrace_cleaner_test.rb:252

F

Failure:
BacktraceCleanerCleanLocationsTest#test_returns_all_clean_locations_(defaults) [test/backtrace_cleaner_test.rb:249]:
--- expected
+++ actual
@@ -1 +1 @@
-["/home/yahonda/src/github.com/rails/rails/activesupport/test/backtrace_cleaner_test.rb"]
+["/home/yahonda/src/github.com/rails/rails/activesupport/test/backtrace_cleaner_test.rb", "/home/yahonda/src/github.com/rails/rails/railties/lib/rails/test_unit/line_filtering.rb"]



bin/test test/backtrace_cleaner_test.rb:247



Finished in 0.005119s, 586.0436 runs/s, 781.3915 assertions/s.
3 runs, 4 assertions, 2 failures, 0 errors, 0 skips
$

The output shows that the tests test_returns_all_clean_locations_(:silent) and test_returns_all_clean_locations_(defaults) are failing. The expected result is that the backtrace cleaner should return only the path to the test file itself. However, the actual result includes an additional path: /home/yahonda/src/github.com/rails/rails/railties/lib/rails/test_unit/line_filtering.rb. This discrepancy indicates that the backtrace cleaner is not behaving as expected, and it's including an extra file in the cleaned backtrace. This unexpected behavior needs further investigation to determine why the additional file is being included and how to correct it. Understanding the root cause will help ensure the backtrace cleaner functions reliably across different environments.

System Configuration

It’s essential to know the system configuration where the issue is occurring. Here are the details:

  • Rails version: main branch
  • Ruby version: ruby 3.4.7 (2025-10-08 revision 7a5688e2a2) +PRISM [x86_64-linux]

Knowing the Rails version (main branch) is crucial because the main branch represents the cutting edge of Rails development. This means the issue might be related to recent changes or updates in the codebase. The Ruby version, 3.4.7, is also important because the behavior of Rails can sometimes vary between different Ruby versions. The +PRISM notation indicates that the Ruby version is using the PRISM parser, which could also be a factor. Understanding these details helps in narrowing down the possible causes of the failure. It's possible that the issue is specific to this particular combination of Rails and Ruby versions, or that it's a more general problem affecting other configurations as well. This information is invaluable for developers trying to reproduce and fix the issue.

Analyzing the Failure

Alright, let's dig into why these tests are failing. From the error output, we can see that the expected backtrace includes only the test file path, but the actual backtrace includes an additional path:

/home/yahonda/src/github.com/rails/rails/railties/lib/rails/test_unit/line_filtering.rb

This suggests that the BacktraceCleaner is not correctly filtering out this file. The BacktraceCleaner is designed to remove irrelevant lines from backtraces to make them easier to read. It uses a set of filters to determine which lines to keep and which to discard. The failure indicates that the filter rules are either not correctly configured or not being applied properly in this specific case. It's possible that a recent change in either the BacktraceCleaner or the test_unit/line_filtering.rb file has introduced this issue. To resolve this, we need to examine the filter rules used by the BacktraceCleaner and understand why line_filtering.rb is not being filtered out. A thorough review of the relevant code and configurations is necessary to pinpoint the exact cause of the failure.

Potential Solutions

So, what can we do to fix this? Here are a few potential solutions:

  1. Review BacktraceCleaner Configuration: Check the configuration of the BacktraceCleaner to ensure that the filter rules are correctly set up. Look for any recent changes that might have altered the filtering behavior. Verify that the regular expressions used to filter out irrelevant lines are still effective and haven't been inadvertently modified.
  2. Examine test_unit/line_filtering.rb: Investigate the test_unit/line_filtering.rb file to see if there have been any recent changes that might cause it to be included in the backtrace. Check if the file is being required or loaded in a way that affects the backtrace. Understanding the file's role in the test environment can provide clues about why it's appearing in the cleaned backtrace.
  3. Update Filter Rules: If the test_unit/line_filtering.rb file should indeed be filtered out, update the filter rules in the BacktraceCleaner to explicitly exclude it. This might involve adding a new regular expression to the list of filters or modifying an existing one. Ensure that the new filter rule doesn't inadvertently exclude other important files.
  4. Investigate Ruby Version Compatibility: Since the issue is occurring with Ruby 3.4.7 +PRISM, it's worth investigating whether there are any compatibility issues between this Ruby version and the BacktraceCleaner. Test the same code with different Ruby versions to see if the problem persists. If it's a Ruby version-specific issue, it might require a patch or workaround.

By systematically exploring these solutions, we can hopefully identify the root cause of the failure and implement a fix to ensure the BacktraceCleaner functions as expected. Each of these steps provides a different angle to approach the problem, increasing the likelihood of finding a resolution.

Conclusion

In summary, the BacktraceCleanerCleanLocationsTest failing in Rails when running via bin/test is an issue that requires careful investigation. By following the steps to reproduce the issue, analyzing the failure, and exploring potential solutions, we can work towards resolving it. Understanding the system configuration and the behavior of the BacktraceCleaner is crucial for finding the root cause and implementing an effective fix. Keeping our tests passing ensures the reliability and stability of the Rails framework, which is essential for all Rails developers. If you encounter this issue, I hope this guide provides you with a solid starting point for troubleshooting. Happy coding, and let's keep Rails running smoothly!