Make Rails Use MiniTest::Spec!

The minitest-spec-rails gem makes it easy to use the MiniTest::Spec DSL within your existing Rails 2.3, 3.x or 4.x test suite. It does this by forcing ActiveSupport::TestCase to utilize the MiniTest::Spec::DSL.

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Usage

Existing or new Rails applications that use the default Rails testing structure can simply drop in the minitest-spec-gem and start writing their tests in the new spec DSL. Since MiniTest::Spec is built on top of MiniTest::Unit, a replacement for Test::Unit, all of your existing tests will continue to work.

Rails 4.1

Our master branch is tracking rails master which is active development for Rails 4.1 which uses minitest 5.0.

For Rails 3.x or 4.0

Our 3-x-stable branch is meant for both Rails 3.x or 4.0 specifically. This version uses the latest 4.x series of minitest.

group :test do
  gem 'minitest-spec-rails'
end

For Rails 2.3

Our 2-3-stable branch tracks our 3.1 version number and is guaranteed to work on any Rails 2.3 version. Since Rails 2.3 does not have a configurable Railtie, we have enabled the mini-shoulda option all the time. This means that if you are on Rails 2.3 under either Ruby 1.8 or 1.9, perhaps using Shoulda, you have a solid upgrade path! Get your tests running with minitest-spec-rails first and nothing in you test stack changes along the way!

group :test do
  gem 'minitest-spec-rails', '~> 3.1'
end

Ruby 1.8 Users!!!

If you are using Ruby 1.8, you must install a Test::Unit shim that subclasses MiniTest::Unit, just as Ruby 1.9 does. We have kindly packed up Ruby 1.9's lib/test directory in the minitest-spec-rails-tu-shim gem. So just add this to your Gemfile.

group :test do
  gem 'minitest-spec-rails-tu-shim'
end

How is this different than MiniTest::Rails?

To start off both Mike Moore (@blowmage) and I have worked together and we both LOVE MiniTest::Spec. Both projects aim to advocate MiniTest and make Rails integration as easy as possible. However, there are a few key differences in our projects. Some of these differences may go away in time too. As always, choose the tool you think fits your needs. So how, is minitest-spec-rails different than minitest-rails?

  • We aim to leverage existing Rails test directories and files!
  • No special test helper and/or generators.
  • Easy migration path for existing Rails applications.
  • How we go about freedom patching Rails.
  • Fully support Ruby 1.8.7 with all legacy Test::Unit behavior.
  • Compatibility with ActiveSupport::TestCase's setup and teardowns.

So the goal of this project is to make Rails 3 or 4 applications just work as if rails-core had decided to support MiniTest::Spec all along. We believe that eventually that day will come and when it does, all your tests will still work! So bundle up and get started!

gem 'minitest-spec-rails'

Test Styles

This cheat sheet shows both the MiniTest::Unit assertions along with the MiniTest::Spec assertion syntax. Remember, MiniTest::Spec is built on top of MiniTest::Unit which is a Test::Unit replacement. That means you can mix and match styles as you upgrade from Test::Unit to a more modern style. For example, both of these would work in MiniTest::Spec and are interchangeable.

# MiniTest::Unit Assertion Style:
assert_equal 100, foo

# MiniTest::Spec Assertion Style:
foo.must_equal 100
require 'test_helper'
class UserTest < ActiveSupport::TestCase
  let(:user_ken)   { User.create! :email => 'ken@metaskills.net' }
  it 'works' do
    user_ken.must_be_instance_of User
  end
end
require 'test_helper'
describe User do
  # This will work too.
end

Just for reference, here is a full list of each of Rails test case classes and the matching describe alternative if one exists. Remember, names are important when using the describe syntax. So, you can not have a mailer named FooBar and expect it to work with the outer describe spec style since there is no way to map the spec type based on an existing naming convention.

# Model Test
class UserTest < ActiveSupport::TestCase
end
describe User do
end

# Controller Test
class UsersControllerTest < ActionController::TestCase
end
describe UsersController do
end

# Integration Tests - Must use subclass style!
class IntegrationTest < ActionDispatch::IntegrationTest
end

# Mailer Test
class UserMailerTest < ActionMailer::TestCase
end
describe UserMailer do
end

# View Helper Test
class UsersHelperTest < ActionView::TestCase
end
describe UsersHelper do
end

Extras

We have baked in a few extra methods behind the scenes to minitest-spec-rails. Most directly support our needs to reflect on described classes, however, they may be useful to you too when meta-programming on top of minitest-spec-rails.

#described_class

The described_class method is available both via a class method and an instance method in any Rails test case. It is guaranteed to work despite the described level too. This allows class level macros to be built, much like Shoulda. Remember, it can only do this if you follow Rails naming conventions for your tests.

class UserTest < ActiveSupport::TestCase
  described_class # => User(id: integer, email: string)
  it 'works here' do
    described_class # => User(id: integer, email: string)
  end
  describe 'and' do
    it 'works here too' do
      described_class # => User(id: integer, email: string)
    end
  end
end

Setup & Teardown Compatability

Rails ActiveSupport::TestCase allows multiple setup and teardown methods per class. It also allows you to specify these either with a symbol or a block. Unlike normal ActiveSupport setup and teardown callbacks, our blocks are evaluated in the scope of the instance, just like before and after. So this just works!

class ActiveSupportCallbackTest < ActiveSupport::TestCase

  setup :foo
  setup :bar
  before { @bat = 'biz' }

  it 'works' do
    @foo.must_equal 'foo'
    @bar.must_equal 'bar'
    @bat.must_equal 'biz'
  end

  private

  def foo ; @foo = 'foo' ; end
  def bar ; @bar = 'bar' ; end

end

mini_shoulda

If you are migrating away from Shoulda, then minitest-spec-rails' mini_shoulda feature will help. To enable it, set the following configuration in your test environment file.

# In config/environments/test.rb
config.minitest_spec_rails.mini_shoulda = true

Doing so only enables a few aliases that allow the Shoulda context, should, and should_eventually methods. The following code demonstrates the full features of the mini_shoulda implementation. It basically replaces the shell of should-context in a few lines of code.

class PostTests < ActiveSupport::TestCase
  setup    { @post = Post.create! :title => 'Test Title', :body => 'Test body' }
  teardown { Post.delete_all }
  should 'work' do
    @post.must_be_instance_of Post
  end
  context 'with a user' do
    should_eventually 'have a user' do
      # ...
    end
  end
end

If you are in the assertions provided by shoulda-context like assert_same_elements, then you may want to consider copying them from here and including them in MiniTest::Spec yourself. I personally recommend just replacing these assertions with something more modern. A few examples are below.

assert_same_elements a, b  # From
a.sort.must_equal b.sort   # To

assert_does_not_contain a, b  # From
a.wont_include b              # To

Matchers

I highly suggest that you stay away from matchers since MiniTest::Spec gives you all the tools you need to write good tests. Staying away from matchers will make your code's tests live longer. So my advice is to stay away from things like .should == and just write .must_equal instead. However, if matchers are really your thing, I recommend the minitest-matchers gem. You can also check out the valid_attribute gem built on top of minitest-matchers.

describe Post do
  subject { Post.new }
  it { must have_valid(:title).when("Hello") }
  it { wont have_valid(:title).when("", nil, "Bad") }
end

Gotchas

Assertion Methods

If you are upgrading from Test::Unit, there are a few missing assertions that have been renamed or are no longer available within MiniTest.

  • The method assert_raise is renamed assert_raises.
  • There is no method assert_nothing_raised. There are good reasons for this on Ryan's blog entry.

Mocha

If you are using Mocha for mocking and stubbing, please update to the latest, 0.13.1 or higher so it is compatible with the latest MiniTest. If you do not like the deprecation warnings in older versions of Rails, just add this below the require 'rails/all' within your application.rb file :)

require 'mocha/deprecation'
Mocha::Deprecation.mode = :disabled

Rails 3.0.x

If you are using minitest-spec-rails with Rails 3.0, then your controller and mailer tests will need to use the tests interface for the assertions to be setup correctly within sub describe blocks. I think this is a bug with class_attribute within Rails 3.0 only. So use the following patterns.

class UsersControllerTest < ActionController::TestCase
  tests UsersController
end
class UserMailerTest < ActionMailer::TestCase
  tests UserMailer
end

Rails 3.1 & 3.2

If your view helper tests give you an eror like this: RuntimeError: In order to use #url_for, you must include routing helpers explicitly., this is something that is broken only for Rails 3.1 and 3.2, both 3.0 and 4.0 and above do not exhibit this error. I have heard that if you include Rails.application.routes.url_helpers in your tests or inject them into the helper module before the test it may work. Lemme know what you find out.

Contributing

We run our tests on Travis CI. If you detect a problem, open up a github issue or fork the repo and help out. After you fork or clone the repository, the following commands will get you up and running on the test suite.

$ bundle install
$ bundle exec rake appraisal:setup
$ bundle exec rake appraisal test

We use the appraisal gem from Thoughtbot to help us generate the individual gemfiles for each Rails version and to run the tests locally against each generated Gemfile. The rake appraisal test command actually runs our test suite against all Rails versions in our Appraisal file. If you want to run the tests for a specific Rails version, use rake -T for a list. For example, the following command will run the tests for Rails 4.1 only.

$ bundle exec rake appraisal:rails41 test

We have a few branches for each major Rails version.

  • 2-3-stable - Tracks Rails 2.3.x with MiniTest 4.x.
  • 3-x-stable - Oddly tracks Rails 3.x and 4.0 with MiniTest 4.x.
  • master - Currently tracks Rails 4.1 which uses Minitest 5.0.

Our current build status is: Build Status