RubyCritic Found Problems Hiding in Plain Sight

Learn how to detect complex methods, duplicate code, and maintainability risks with a single HTML report

What is RubyCritic?

RubyCritic is a code quality analysis tool for Ruby and Rails projects. It combines tools such as Reek, Flay, and Flog to identify:

• Complex methods
• Duplicate code
• Code smells
• Maintainability issues

It generates an HTML report with grades ranging from A (best) to F (worst).

1. Install RubyCritic

Add it to your Gemfile:

group :development, :test do
  gem 'rubycritic', require: false
end

Install dependencies:

bundle install

2. Run an Analysis

From the project root:

bundle exec rubycritic .

RubyCritic generates an HTML report, typically in:

tmp/rubycritic/overview.html

Open it in your browser:

xdg-open tmp/rubycritic/overview.html   # Linux
open tmp/rubycritic/overview.html       # macOS

3. Useful Options

Analyze only recent changes:

bundle exec rubycritic --mode-ci

Generate a report in a custom directory:

bundle exec rubycritic \
  --no-browser \
  --format html \
  --path analysis_report

4. Common Findings

IrresponsibleModule

A class lacks documentation.

# Responsible for extracting property data from listing pages.
class PropertyCrawler
end

TooManyStatements

A method is too large.

Fix: Break it into smaller methods.

UncommunicativeVariableName

Variable names are unclear.

rescue StandardError => error
  puts error.message
end

VeryHighComplexity

A method does too many things.

Fix: Extract responsibilities into dedicated methods.

DuplicateCode / DuplicateMethodCall

Repeated code or method calls.

Fix: Create reusable helpers or service methods.

UtilityFunction

The method does not depend on instance state.

Fix: Consider moving it to a module or class method.

5. Understanding the Report

| Section     | Description                                         |
|------------ |-----------------------------------------------------|
| Overview    | Overall project grade and summary metrics           |
| Files       | Quality score and analysis for each file            |
| Smells      | Code maintainability issues and design problems     |
| Churn       | Frequently modified files that may need attention   |
| Duplication | Repeated or duplicated code detected in the project |

Focus first on files with:

• High churn
• High complexity
• Many smells

These usually provide the greatest return on refactoring effort.

6. Refactoring Strategy

1. Review the overall grade.
2. Prioritize files with high churn and complexity.
3. Remove duplication.
4. Split large methods.
5. Improve naming and readability.
6. Run tests.
7. Re-run RubyCritic and compare results.

bundle exec rubycritic \
  --no-browser \
  --format html \
  --path analysis_report

Key Takeaway

RubyCritic does not tell you that your code is bad — it highlights areas that may become difficult to maintain. Treat its findings as guidance, prioritize the most impactful issues, and improve the code incrementally.