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https://github.com/deep-cover/deep-cover

The best coverage tool for Ruby code
https://github.com/deep-cover/deep-cover

branch-coverage coverage ruby

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The best coverage tool for Ruby code

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[![Build Status](https://travis-ci.org/deep-cover/deep-cover.svg?branch=master)](https://travis-ci.org/deep-cover/deep-cover)

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# Maintenance status



Deep Cover has not been updated for Ruby 3.x new syntax features, in particular:



- pattern match

- `{x:}` notation



Unfortunately, both co-authors are occupied contributing to other projects and can offer only minimal maintenance: complete PRs will be accepted and we welcome applications if you are interested in becoming a maintainer for this project.



# DeepCover



Deep Cover aims to be the best coverage tool for Ruby code:



- more accurate line coverage

- branch coverage

- can be used as a drop-in replacement for the built-in Coverage library.



It reports a more accurate picture of your code usage. In particular a line is considered covered if and only if it is entirely executed:



```

def foo(something: false)

  bar if something  # => This is considered covered by builtin coverage,

                    #    even though `bar` might not even exist

end



# somewhere in a test:

foo

```



Optionally, branch coverage will detect if some branches are never taken. In the following example, `test_foo` only provides values for `x` that respond to `:to_s`, thus the implicit `else` is never tested (i.e. a value of `x` that does not respond to `:to_s`)



```

def foo(x)

  x = x.to_s if x.respond_to? :to_s

  # ...

end



def test_foo

  assert_equal something, foo(42)

  assert_equal something_else, foo(:hello)

end

```



## Examples



These examples are direct outputs from our HTML reporter:



- [Rails' `activesupport`](https://deep-cover.github.io/rails-cover/activesupport/)

- [Rails' `activerecord`](https://deep-cover.github.io/rails-cover/activerecord/)



## DeepCover vs builtin coverage



| Feature          |    MRI    |    DeepCover     |

| ---------------- | :-------: | :--------------: |

| Line coverage    |  partial  |        ✓         |

| Node coverage    |    no     |        ✓         |

| Branch coverage  |  partial  |        ✓         |

| Method coverage  |     ✓     |        ~         |

| Slowdown         |   < 1%    |       ~20%       |

| Platform support | Ruby 2.5+ | Ruby 2.1+, JRuby |



**Line coverage**: MRI doesn't cover some lines (e.g. `when some_value`).



**Node coverage**: MRI provides no way to tell which parts of any line is evaluated (e.g. `0.times { never_run }`). DeepCover covers everything.



**Method coverage**: MRI considers every method defined, including methods defined on objects or via `define_method`, `class_eval`, etc. For Istanbul output, DeepCover has a different approach and covers all `def` and all blocks.



| **Branch coverage**     | MRI | DeepCover |

| ----------------------- | :-: | :-------: |

| `if` / `unless` / `?:`  |  ✓  |     ✓     |

| `case` / `when`         |  ✓  |     ✓     |

| `❘❘` / `&&`             | no  |     ✓     |

| `foo&.bar`              |  ✓  |     ✓     |

| `{❘foo = 42, bar: 43❘}` | no  |     ✓     |

| `while` / `until`       |  ✓  |     !     |



_Note on loops (!)_: DeepCover doesn't consider loops to be branches, but it's

easy to support it if needed.



## Installation



Do the appropriate of the installation of the gem, then follow the steps that correspond to your situation.



    # if the project is a gem, add this to your .gemspec and then run `bundle install`

    spec.add_development_dependency 'deep-cover', '~> 0.7'



    # otherwise if using a Gemfile, add this to it and then run `bundle install`

    gem 'deep-cover', '~> 0.7', group: :test



    # otherwise just run:

    gem install deep-cover



### Trying `deep-cover` quickly



An easy way to try `deep-cover`, without any configuration needed:



    deep-cover clone command to run test

    # ex:

    deep-cover clone rake test



Check the produced `coverage/index.html`.



Note, this is a bit slower and may cause issues in your tests if your use relative paths that lead outside of the directory (Such as a dependency that is in a parent directory).



### Regular setup



1. Require `deep-cover`



   You must call `require 'deep-cover'` **before** the code you want to cover is loaded.



   Typically, you want to insert that line **at the very top** of `test/test_helper.rb` or `spec/spec_helper.rb` . If `deep-cover` is required after your code, then it won't be able to detect the coverage.



   Note that if some of your tests run by launching another process, that process will have to `require 'deep-cover'` also. For example you could insert `require 'deep-cover' if ENV['DEEP_COVER']` at the beginning of `lib/my_awesome_gem.rb`, before all the `require_relative 'my_awesome_gem/fabulous_core_part_1'`, ...

   Note that the environment variable `DEEP_COVER` is set by `deep-cover exec` or `DeepCover.start`.



2. Create a config file (optional)



   You may want to create a config file `.deep_cover.rb` at the root of your project, where you can set the config as you wish.



   ```

   # File .deep_cover.rb

   DeepCover.configure do

     ignore_uncovered :default_argument

     # ...

   end

   ```



3. Launch it



   Even after `DeepCover` is `require`d and configured, only a very minimal amount of code is actually loaded and coverage is _not started_.



   The easiest way to actually start it is to use `deep-cover exec`



   For example:



   ```

   $ deep-cover exec rspec

   # ...all the output of rspec

   # ...coverage report

   ```



### Already using SimpleCov / builtin Coverage



To make it easier to transition for projects already using the builtin `Coverage` library (such as those using `SimpleCov`), `deep-cover` can inject itself into those tools so that, while you still only have line-by-line coverage information, it becomes stricter, only marking a line as executed if _everything_ on it has been executed.



You must call `require 'deep_cover/builtin_takeover'` **before** you require the coverage tool that you normally use.



For example, the `test/test_helper.rb` file for `SimpleCov` users will look like



```

require 'deep_cover/builtin_takeover'

require 'simplecov'

SimpleCov.start

# rest of `test_helper.rb`

```



Once this is done, simply generate the coverage as you normally would. In order to get detailed information about why a line is not covered, you will need to the regular `deep-cover` mode.



### Online coverage tools such as Code Climate, Coveralls, Codecov



At the moment, those tools do not support deep-cover. It is however possible to use the takeover system to, at least, make them stricter. Follow the explanation in the above section for injecting into `SimpleCov`.



## Usage



### Configuration



`configure` is used to specify how specific `DeepCover` should be and which files it should analyse. The following code reflects the default settings:



```

DeepCover.configure do

  ignore_uncovered :raise, :default_argument

  detect_uncovered :trivial_if

  paths %w[app lib]

  exclude_paths ['fixtures', /^lib\/ignore/]

end

```



The file `.deep_cover.rb` is loaded automatically when requiring `deep-cover` and is the best place to put the configuration.



#### Custom filters



`deep-cover` comes with a few filters that make it possible to ignore certain uncovered codes.



It is easy to add you own filters.



For example, if one wants to ignore uncovered calls to `raise` but the code uses `our_custom_raise` instead, the following with work:



```

DeepCover.configure do

  ignore_uncovered do

    type == :send &&

      receiver == nil &&

      message == :our_custom_raise

  end

end

```



## Development



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



For detailed analysis:



`deep-cover -d -e "if(:try_me); puts 'cool'; end"`



To run one of the specs in `spec`:



`bin/cov boolean`



More details in the [contributing guide](https://github.com/deep-cover/deep-cover/blob/master/CONTRIBUTING.md).



## Contributing



Please ask questions on StackOverflow.com. Maintainers monitor the tag `deep-cover.rb`.



Bug reports and pull requests are welcome on GitHub at https://github.com/deep-cover/deep-cover. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [Contributor Covenant](http://contributor-covenant.org) code of conduct.



## Contributors



This project exists thanks to all the people who contribute. [[Contribute](CONTRIBUTING.md)].




## License



The gem is available as open source under the terms of the [MIT License](http://opensource.org/licenses/MIT).



## Code of Conduct



Everyone interacting in the DeepCover project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the [code of conduct](https://github.com/deep-cover/deep-cover/blob/master/CODE_OF_CONDUCT.md).