Code Coverage highlighting

1. Install the Coverage Gutters extension and click the Watch icon added to the footer
2. Add Simplecov and Simplecov-lcov to Gemfile:

group :test do
  gem 'simplecov'
  gem 'simplecov-lcov'
end

3. Add the lcov formatter to SimpleCov initialization:

# spec/test_helper.rb
SimpleCov::Formatter::LcovFormatter.config do |c|
  c.report_with_single_file = true
  c.output_directory = 'coverage'
  c.lcov_file_name = 'lcov.info'
end
SimpleCov.start do
  enable_coverage :branch
  formatter SimpleCov::Formatter::MultiFormatter.new(
    [
      SimpleCov::Formatter::LcovFormatter,
      SimpleCov::Formatter::HTMLFormatter
    ]
  )
end

Voila! Now when hitting CTRL + S on any file from /app folder I do get coverage higlights in gutter:

Extension Configuration

Every project is different so it might be that you have to change some configuration options as it’s set up to support RSpec by default:

• railsAutomaticTestRunner.framework: Specifies which framework is used to execute test commands: rspec or minitest.
• railsAutomaticTestRunner.testsDirectory: Specifies the folder where your test files are located, the default directory is spec.
• railsAutomaticTestRunner.bundleExec: Append bundle exec before test command?
• railsAutomaticTestRunner.envVariables: Pass any environment variables as a string there, eg: CRUCIAL_API_KEY=test
• railsAutomaticTestRunner.args: Pass any arguments like --fail-fast as a string there
• railsAutomaticTestRunner.automaticOutputDisplay: Automatically switch to the output tab, when enabled might interrupt terminal work.