simplecov

SimpleCov Test Coverage Agent

Overview

Maintain high test coverage in Ruby and Rails applications through automated analysis using SimpleCov as the coverage engine and SimpleCov Console for terminal output. This skill identifies coverage gaps, suggests targeted tests, and enforces quality standards alongside RubyCritic for comprehensive code quality feedback.

Core Capabilities

1. Setup and Configuration

Configure SimpleCov for any Ruby/Rails project with best practices:

Initial Setup:

# Add to Gemfile
echo "gem 'simplecov', require: false, group: :test" >> Gemfile
echo "gem 'simplecov-console', require: false, group: :test" >> Gemfile
bundle install

Create .simplecov Configuration:

SimpleCov.start 'rails' do
  formatter SimpleCov::Formatter::MultiFormatter.new([
    SimpleCov::Formatter::HTMLFormatter,
    SimpleCov::Formatter::Console
  ])

  # Enable branch coverage (Ruby 2.5+)
  enable_coverage :branch
  primary_coverage :branch

  # Set thresholds
  minimum_coverage line: 90, branch: 80
  minimum_coverage_by_file 80
  refuse_coverage_drop :line, :branch

  # Standard Rails filters
  add_filter '/test/'
  add_filter '/spec/'
  add_filter '/config/'
  add_filter '/vendor/'

  # Organize by application layers
  add_group 'Controllers', 'app/controllers'
  add_group 'Models', 'app/models'
  add_group 'Services', 'app/services'
  add_group 'Jobs', 'app/jobs'
  add_group 'Mailers', 'app/mailers'
  add_group 'Helpers', 'app/helpers'
  add_group 'Libraries', 'lib'
end

Console Formatter Options:

# Customize output in .simplecov
SimpleCov::Formatter::Console.use_colors = true
SimpleCov::Formatter::Console.sort = 'coverage'  # or 'path'
SimpleCov::Formatter::Console.show_covered = false
SimpleCov::Formatter::Console.max_rows = 15
SimpleCov::Formatter::Console.output_style = 'table'  # or 'block'

Test Helper Integration (CRITICAL - Must be FIRST):

# test/test_helper.rb or spec/spec_helper.rb
require 'simplecov'
SimpleCov.start 'rails'

# Now load application
ENV['RAILS_ENV'] ||= 'test'
require_relative '../config/environment'
# ... rest of test helper