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A SimpleCov formatter for test driven development
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A SimpleCov formatter for test driven development. Displays code coverage results in the console for single files

Example TDD


Add this line to your application's Gemfile:

gem 'simplecov-tdd'

And then execute:

$ bundle

Or install it yourself as:

$ gem install simplecov-tdd


  1. Ensure that you've configured your project to SimpleCov's Getting Started section:
  2. Set your SimpleCov configuration to the following:
require "simplecov/tdd"
SimpleCov.formatter = Simplecov::Formatter::Tdd
# OR use multi-formatter
SimpleCov.formatters =[

Simple Setup:

# /spec/spec_helper.rb
require "simplecov"
require "simplecov/tdd"
SimpleCov.formatter = SimpleCov::Formatter::Tdd
SimpleCov.start 'rails'
  1. Run your tests using rspec path/to/file_spec.rb or guard
  2. Fix the missing coverage
  3. 💰 Profit! 💰

Configuration options

There are a few configuration options that may be set before formatting is called. Generally you may place these after SimpleCov.formatter or SimpleCov.formatters = in your setup.

output_style (default: :simple)

When there are lines missing coverage, this option determines how to display output. The accepted values are :simple (default) or :verbose.

SimpleCov::Formatter::Tdd.output_style = :verbose

Here's an example of what :verbose output looks like:

90.0% coverage, 167 total lines

The following 2 lines have missing coverage:
[5, 25]

line | source code
5 => obj.is_a?(SomeClass)
25 => SomeClass.explode!

debug_mode (default: false)

This is useful for determining if the current file being tested doesn't have a match from SimpleCov's file list.

SimpleCov::Formatter::Tdd.debug_mode = true

Future Features

  • Support for minitest


After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to


Bug reports and pull requests are welcome on GitHub at This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

Code of Conduct

Everyone interacting in the Simplecov::Tdd project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.

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