Rails RSpec setup

RSpec is an awesome tool for testing Rails apps. It is a hugely popular  BDD-oriented (**B**ehavior **D**riven **D**evelopment) testing framework in the Ruby community.

It makes writing tests simpler, more expressive and easier to maintain!

##Getting started
First, you'll need to install Rspec but you’ll also need [Database Cleaner](https://github.com/DatabaseCleaner/database_cleaner) to help hold things together and ensure a clean state during tests. Add the following gems to the :test and :development groups in your Gemfile and then run `bundle install`:
```
group :development, :test do
  gem "database_cleaner"
  gem "rspec-rails"
end
```
##Configuring RSpec
Before you can start with writing your RSpec tests your will need to run `rails generate rspec:install`. This will create the following files:
```
create  .rspec
create  spec
create  spec/spec_helper.rb
create  spec/rails_helper.rb
```
Files such as **spec_helper.rb** and **rails_helper.rb** contain the default RSpec set up with lots of comments. It is *strongly* recommended to read through all of those comments to get a good understanding of what each option does.
###spec_helper.rb
spec_helper.rb file is used to configure RSpec. The base configuration file, after uncommenting some useful configuration options, is written in the following way:

```
RSpec.configure do |config|
  config.expect_with :rspec do |expectations|
    expectations.include_chain_clauses_in_custom_matcher_descriptions = true
  end

  config.mock_with :rspec do |mocks|
    mocks.verify_partial_doubles = true
  end

  config.shared_context_metadata_behavior = :apply_to_host_groups
  config.filter_run_when_matching :focus
  config.disable_monkey_patching!
  
  if config.files_to_run.one?
    config.default_formatter = "doc"
  end
  
  config.profile_examples = 10
  
  config.order = :random
  Kernel.srand config.seed
end
```

- ```expectations.include_chain_clauses_in_custom_matcher_descriptions = true``` - [Chain method](https://relishapp.com/rspec/rspec-expectations/docs/custom-matchers/define-matcher-with-fluent-interface) allows custom matcher descriptions and failure messages to include text for helper methods.
* `mocks.verify_partial_doubles = true` - [Partial doubles](http://relishapp.com/rspec/rspec-mocks/docs/verifying-doubles/partial-doubles) prevent you from stubbing any methods that don’t already exist on an object, it typo-proofs your mocks.
* `config.shared_context_metadata_behavior = :apply_to_host_groups` - [Shared context metadata](http://www.rubydoc.info/github/rspec/rspec-core/RSpec%2FCore%2FConfiguration%3Ashared_context_metadata_behavior) configures how RSpec treats metadata passed as part of a shared example group definition.
* `filter_run_when_matching` - [Filter run when matching](https://relishapp.com/rspec/rspec-core/docs/filtering/filter-run-when-matching) allows you to limit a spec run to individual examples or groups you tagged with `:focus` metadata.
* `disable_monkey_patching!` - [Prevents RSpec from monkey patching](https://relishapp.com/rspec/rspec-core/v/3-5/docs/configuration/zero-monkey-patching-mode) makes objects behave in tests as they would in "real" life.
* `default_formatter` - [Default formatter](https://relishapp.com/rspec/rspec-core/v/2-5/docs/command-line/format-option) sets up the default format of your rspec tests that will be used if no formatter has been set.
* `config.profile_examples` - [Profile examples](https://relishapp.com/rspec/rspec-core/docs/configuration/profile-examples) print the slowest examples and example groups at the end of the spec run, but it slows down your suite
* `config.order = :random` and `Kernel.srand config.seed` - Configure tests to run in a [random order](https://relishapp.com/rspec/rspec-core/v/3-5/docs/command-line/order). This helps to keep each test independent of one another. 

###rails_helper.rb
rails_helper.rb file is used for specs which depend on Rails (nearly every part of a Rails projects). 
rails_helper.rb requires spec_helper.rb to work.

```
require 'spec_helper'
ENV['RAILS_ENV'] ||= 'test'
require File.expand_path('../../config/environment', __FILE__)
abort("The Rails environment is running in production mode!") if Rails.env.production?
require 'rspec/rails'

ActiveRecord::Migration.maintain_test_schema!

RSpec.configure do |config|
  config.fixture_path = "#{::Rails.root}/spec/fixtures"
  config.use_transactional_fixtures = true
  config.infer_spec_type_from_file_location!
  config.filter_rails_from_backtrace!
end
```

* `fixture_path` - [File fixture](https://relishapp.com/rspec/rspec-rails/v/3-5/docs/file-fixture) is a normal file stored in spec/fixtures by default.
* `use_transactional_fixtures` - [Transactional](https://relishapp.com/rspec/rspec-rails/docs/transactions) fixtures allow records created for one test to be visible for the next test.
* `infer_spec_type_from_file_location!` -  Allows to automatically [tag specs in directories](https://relishapp.com/rspec/rspec-rails/docs/directory-structure) with matching type metadata so that they have relevant helpers available to them.
* `filter_rails_from_backtrace!` - [Backtrace filtering](https://relishapp.com/rspec/rspec-rails/docs/backtrace-filtering) is used to filter out lines in backtraces that come from Rails gems in order to reduce the noise in test failure output.
##Configuring Database Cleaner
By configuring the **Database Cleaner** in your application, you make it sure that tests start with a clean state. The only thing you need to do is to add the following to your RSpec.configure block in rails_helper.rb:
```
config.before(:suite) do
  DatabaseCleaner.clean_with(:truncation)
end
```

##How to run the tests?
Once everything is configured you are ready to go! There are four ways to run your test:
- Everything at once: `bundle exec rspec`. 
This runs all your tests.
- One RSpec package: `bundle exec rspec ./spec/models`
This runs all model specs.
- One RSpec file at a time: `bundle exec rspec ./spec/models/story_spec.rb`. 
This runs only tests in Story model.
- One by one: `bundle exec rspec ./spec/models/story_spec.rb:10`
This runs only tests on line 10 in Story model.

Be careful! The more tests there are the longer it takes to compile them. Only run tests for what you really need!


We hope this article helped you get your tests up and running!

Originally published on [kolosek.com](https://kolosek.com/rails-rspec-setup/).