Single Cov

Actionable code coverage.

rspec spec/foobar_spec.rb
......
114 example, 0 failures

lib/foobar.rb new uncovered lines introduced (2 current vs 0 configured)",
Uncovered lines:
lib/foobar.rb:22
lib/foobar.rb:23:6-19

Missing coverage on every 💚 test run
Catch coverage issues before making PRs
Easily add coverage enforcement for legacy apps
2-5% runtime overhead on small files, compared to 20% for SimpleCov
Branch coverage on ruby 2.5+ (disable via branches: false)
Use with forking_test_runner for per test coverage

# Gemfile
gem 'single_cov', group: :test

# spec/spec_helper.rb ... load before loading rails / minitest / libraries
require 'single_cov'
SingleCov.setup :rspec

# spec/foobar_spec.rb ... add covered! call to test files
require 'spec_helper'
SingleCov.covered!

describe "xyz" do ...

Minitest

Call setup before loading minitest.

SingleCov.setup :minitest
require 'minitest/autorun'

Unfound target file

# change all guessed paths
SingleCov.rewrite { |f| f.sub('lib/unit/', 'app/models/') }

# mark directory as being in app and not lib
SingleCov::APP_FOLDERS << 'presenters'

# add 1-off
SingleCov.covered! file: 'scripts/weird_thing.rb'

Known uncovered

Add the inline comment # uncovered to not be alerted about it being uncovered.

Prevent addition of new uncovered code, without having to cover all existing code.

Alternatively mark how many lines are uncovered:

SingleCov.covered! uncovered: 4

Verify all code has tests & coverage

# spec/coverage_spec.rb
SingleCov.not_covered! # not testing any code in lib/

describe "Coverage" do
  it "does not allow new untested code" do
    # option :tests to pass custom Dir.glob results
    SingleCov.assert_used
  end

  it "does not allow new untested files" do
    # option :tests and :files to pass custom Dir.glob results
    # :untested to get it passing with known untested files
    SingleCov.assert_tested
  end
end

Automatic bootstrap

Run this from irb to get SingleCov added to all test files.

tests = Dir['spec/**/*_spec.rb']
command = "bundle exec rspec %{file}"

tests.each do |f|
  content = File.read(f)
  next if content.include?('SingleCov.')

  # add initial SingleCov call
  content = content.split(/\n/, -1)
  insert = content.index { |l| l !~ /require/ && l !~ /^#/ }
  content[insert...insert] = ["", "SingleCov.covered!"]
  File.write(f, content.join("\n"))

  # run the test to check coverage
  result = `#{command.sub('%{file}', f)} 2>&1`
  if $?.success?
    puts "#{f} is good!"
    next
  end

  if uncovered = result[/\((\d+) current/, 1]
    # configure uncovered
    puts "Uncovered for #{f} is #{uncovered}"
    content[insert+1] = "SingleCov.covered! uncovered: #{uncovered}"
    File.write(f, content.join("\n"))
  else
    # mark bad tests for manual cleanup
    content[insert+1] = "# SingleCov.covered! # TODO: manually fix this"
    File.write(f, content.join("\n"))
    puts "Manually fix: #{f} ... output is:\n#{result}"
  end
end

Author

Michael Grosser
michael@grosser.it
License: MIT