SimpleCov

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Introduction

SimpleCov is the standard code coverage tool for Ruby. It uses Ruby’s built-in Coverage library to gather data while your tests run, and adds a configuration API and reporting on top, so you can see which lines and branches your RSpec, Minitest or Cucumber suites exercise.

Setup is a two-line addition at the very top of your test helper: require "simplecov" and SimpleCov.start (with a "rails" profile available for Rails apps). The default HTML formatter produces a browsable report in coverage/index.html. Configuration covers filters to exclude paths, groups to organise the report (models, controllers and so on), branch coverage (enable_coverage :branch), merging results from multiple test suites or parallel processes, and minimum_coverage or minimum_coverage_by_file thresholds that fail the build. Community formatters output LCOV, Cobertura and JSON for CI services. Version 1.3.2 was released on 30 September 2026.

The source code is at simplecov-ruby/simplecov on GitHub under the MIT licence, with about 4,900 stars; the most recent commit was on 10 November 2026.

Features

1. Easy setup: Two lines in your test helper.
2. HTML report: Browsable line and branch coverage.
3. Thresholds: minimum_coverage fails builds below target.
4. Merging: Combine results across suites and parallel runs.

Pros

1. Free to use: Open source under the MIT licence, so the core tool costs nothing to use.
2. Actively maintained: The repository had commits as recent as 10 November 2026.
3. Community: About 4,900 GitHub stars.

Cons

1. Must load first: Starting SimpleCov after app code loads gives wrong results.
2. Extra formatters for CI: LCOV or Cobertura output needs add-on gems.

Usage and Links (Example)

# spec/spec_helper.rb or test/test_helper.rb (first lines)
require "simplecov"
SimpleCov.start "rails" do
  enable_coverage :branch
  minimum_coverage line: 90, branch: 80
  add_filter "/vendor/"
  add_group "Services", "app/services"
end

bundle exec rspec   # open coverage/index.html

Resources:

• SimpleCov website

Pricing

SimpleCov is free and open source under the MIT licence.

Recommended for?

1. Every Ruby project that wants coverage visibility.
2. CI pipelines enforcing coverage thresholds.

Conclusion

SimpleCov is the essential Ruby coverage tool, easy to set up and flexible enough for large Rails applications.