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Transpec

Transpec is a tool for converting your specs to the latest RSpec syntax with static and dynamic code analysis.

This aims to facilitate smooth transition to RSpec 3, and it's now ready for RSpec 2.99 and 3.0 beta!

See the following pages for the new RSpec syntax and the plan for RSpec 3:

Transpec now supports almost all conversions for the RSpec changes, but the changes for RSpec 3 is not fixed and may vary in the future. So it's recommended to follow updates of both RSpec and Transpec.

Examples

Here's an example spec:

describe Account do
  subject(:account) { Account.new(logger) }
  let(:logger) { mock('logger') }

  describe '#balance' do
    context 'initially' do
      it 'is zero' do
        .balance.should == 0
      end
    end
  end

  describe '#close' do
    it 'logs an account closed message' do
      logger.should_receive(:account_closed).with()
      .close
    end
  end

  describe '#renew' do
    context 'when the account is renewable and not closed' do
      before do
        .stub(:renewable? => true, :closed? => false)
      end

      it 'does not raise error' do
        lambda { .renew }.should_not raise_error(Account::RenewalError)
      end
    end
  end
end

Transpec would convert it to the following form:

describe Account do
  subject(:account) { Account.new(logger) }
  let(:logger) { double('logger') }

  describe '#balance' do
    context 'initially' do
      it 'is zero' do
        expect(.balance).to eq(0)
      end
    end
  end

  describe '#close' do
    it 'logs an account closed message' do
      expect(logger).to receive(:account_closed).with()
      .close
    end
  end

  describe '#renew' do
    context 'when the account is renewable and not closed' do
      before do
        allow().to receive(:renewable?).and_return(true)
        allow().to receive(:closed?).and_return(false)
      end

      it 'does not raise error' do
        expect { .renew }.not_to raise_error
      end
    end
  end
end

Actual examples

You can see actual conversion examples below:

Installation

Simply install transpec with gem command:

$ gem install transpec

Usually you don't need to add transpec to your *.gemspec or Gemfile since this isn't a tool to be used daily.

Basic Usage

Before converting your specs:

  • Make sure your project has rspec gem dependency 2.14 or later. If not, change your *.gemspec or Gemfile to do so.
  • Run rspec and check if all the specs pass.
  • Ensure the Git repository is clean. (You don't want to mix up your changes and Transpec's changes, right?)

Then, run transpec in the project root directory:

$ cd some-project
$ transpec
Copying the project for dynamic analysis...
Running dynamic analysis with command "bundle exec rspec"...
...............................................................................
...................

Finished in 13.07 seconds
100 examples, 0 failures

Converting spec/spec_helper.rb
Converting spec/support/cache_helper.rb
Converting spec/support/file_helper.rb
Converting spec/support/shared_context.rb
Converting spec/transpec/ast/node_spec.rb

This will run the specs, convert them, and overwrite all spec files in the spec directory.

After the conversion, run rspec again and check whether everything is green:

$ bundle exec rspec

If it's green, commit the changes with an auto-generated message that describes the conversion summary:

$ git commit -aeF .git/COMMIT_EDITMSG

And you are done!

Upgrade Process to RSpec 3 beta

If you are going to use Transpec in the upgrade process to RSpec 3 beta, read the article by Myron Marston:

Options

-f/--force

Force processing even if the current Git repository is not clean.

$ git status --short
 M spec/spec_helper.rb
$ transpec
The current Git repository is not clean. Aborting.
$ transpec --force
Copying project for dynamic analysis...
Running dynamic analysis with command "bundle exec rspec"...

-s/--skip-dynamic-analysis

Skip dynamic analysis and convert with only static analysis. Note that specifying this option decreases the conversion accuracy.

-c/--rspec-command

Specify a command to run your specs that is used for dynamic analysis.

Transpec needs to run your specs in a copied project directory for dynamic analysis. If your project requires some special setups or commands to run specs, use this option. bundle exec rspec is used by default.

$ transpec --rspec-command "./special_setup.sh && bundle exec rspec"

-k/--keep

Keep specific syntaxes by disabling conversions.

$ transpec --keep should_receive,stub

Available syntax types

Type Target Syntax Converted Syntax
should obj.should matcher expect(obj).to matcher
oneliner it { should ... } it { is_expected.to ... }
should_receive obj.should_receive expect(obj).to receive
stub obj.stub allow(obj).to receive
have_items expect(obj).to have(n).items expect(obj.size).to eq(n)
its its(:attr) { } describe { subject { }; it { } }
deprecated obj.stub!, mock('foo'), etc. obj.stub, double('foo')

See Supported Conversions for more details.

-n/--negative-form

Specify a negative form of to that is used in the expect syntax. Either not_to or to_not. not_to is used by default.

$ transpec --negative-form to_not

-b/--boolean-matcher

Specify a matcher type that be_true and be_false will be converted to. Any of truthy,falsey, truthy,falsy or true,false can be specified. truthy,falsey is used by default.

$ transpec --boolean-matcher true,false

See Supported Conversions - Boolean matchers for more details.

-p/--no-parentheses-matcher-arg

Suppress parenthesizing arguments of matchers when converting should with operator matcher to expect with non-operator matcher (the expect syntax does not directly support the operator matchers). Note that it will be parenthesized even if this option is specified when parentheses are necessary to keep the meaning of the expression.

describe 'original spec' do
  it 'is an example' do
    1.should == 1
    2.should > 1
    'string'.should =~ /^str/
    [1, 2, 3].should =~ [2, 1, 3]
    { key: value }.should == { key: value }
  end
end

describe 'converted spec' do
  it 'is an example' do
    expect(1).to eq(1)
    expect(2).to be > 1
    expect('string').to match(/^str/)
    expect([1, 2, 3]).to match_array([2, 1, 3])
    expect({ key: value }).to eq({ key: value })
  end
end

describe 'converted spec with -p/--no-parentheses-matcher-arg option' do
  it 'is an example' do
    expect(1).to eq 1
    expect(2).to be > 1
    expect('string').to match /^str/
    expect([1, 2, 3]).to match_array [2, 1, 3]
    # With non-operator method, the parentheses are always required
    # to prevent the hash from being interpreted as a block.
    expect({ key: value }).to eq({ key: value })
  end
end

Inconvertible Specs

You might see the following warning while conversion:

Cannot convert #should into #expect since #expect is not available in the context.
spec/awesome_spec.rb:4:      1.should == 1

This message would be shown with specs like:

describe '#should that cannot be converted to #expect' do
  class MyAwesomeTestRunner
    def run
      1.should == 1
    end
  end

  it 'is 1' do
    test_runner = MyAwesomeTestRunner.new
    test_runner.run
  end
end

Reason

  • should is defined on BasicObject class, so you can use should everywhere.
  • expect is defined on RSpec::Matchers module that is included by RSpec::Core::ExampleGroup class, so you can use expect only where self is an instance of RSpec::Core::ExampleGroup (i.e. in it blocks, :each hook blocks or included module methods) or other classes that explicitly include RSpec::Matchers.

With the above example, in the context of 1.should == 1, the self is an instance of MyAwesomeTestRunner. Transpec tracks contexts and skips conversion if the target syntax cannot be converted in a case like this.

Solution

Include or extend RSpec::Matchers module to make expect available in the context:

  class MyAwesomeTestRunner
    include RSpec::Matchers

    def run
      1.should == 1
    end
  end

Then run transpec again.

Supported Conversions

Standard expectations

# Targets
obj.should matcher
obj.should_not matcher

# Converted
expect(obj).to matcher
expect(obj).not_to matcher
expect(obj).to_not matcher # with `--negative-form to_not`

One-liner expectations

This conversion is available only if your project has rspec gem dependency 2.99.0.beta2 or later.

# Targets
it { should matcher }
it { should_not matcher }

# Converted
it { is_expected.to matcher }
it { is_expected.not_to matcher }
it { is_expected.to_not matcher } # with `--negative-form to_not`

is_expected.to is designed for the consistency with the expect syntax. However the one-liner should is still not deprecated in RSpec 3.0 and available even if the should syntax is disabled with RSpec.configure. So if you think is_expected.to is verbose, feel free to disable this conversion and continue using the one-liner should.

Operator matchers

# Targets
1.should == 1
1.should < 2
Integer.should === 1
'string'.should =~ /^str/
[1, 2, 3].should =~ [2, 1, 3]

# Converted
expect(1).to eq(1)
expect(1).to be < 2
expect(Integer).to be === 1
expect('string').to match(/^str/)
expect([1, 2, 3]).to match_array([2, 1, 3])

This conversion is combined with the conversion of standard expectations and cannot be disabled separately because the expect syntax does not directly support the operator matchers.

Boolean matchers

This conversion is available only if your project has rspec gem dependency 2.99.0.beta1 or later.

# Targets
expect(obj).to be_true
expect(obj).to be_false

# Converted
expect(obj).to be_truthy
expect(obj).to be_falsey

# With `--boolean-matcher truthy,falsy`
# be_falsy is just an alias of be_falsey.
expect(obj).to be_truthy
expect(obj).to be_falsy

# With `--boolean-matcher true,false`
expect(obj).to be true
expect(obj).to be false
  • be_true matcher passes if expectation subject is truthy in conditional semantics. (i.e. all objects except false and nil)
  • be_false matcher passes if expectation subject is falsey in conditional semantics. (i.e. false or nil)
  • be_truthy and be_falsey matchers are renamed version of be_true and be_false and their behaviors are same.
  • be true and be false are not new things. These are combinations of be matcher and boolean literals. These pass if expectation subject is exactly equal to boolean value.

So, converting be_true/be_false to be_truthy/be_falsey never breaks your specs and this is the Transpec's default. If you are willing to test boolean values strictly, you can convert them to be true/be false with --boolean-matcher true,false option. Note that this may break your specs if your application codes don't return exact boolean values.

be_close matcher

# Targets
expect(1.0 / 3.0).to be_close(0.333, 0.001)

# Converted
expect(1.0 / 3.0).to be_within(0.001).of(0.333)

have(n).items matcher

This conversion will be disabled automatically if rspec-collection_matchers or rspec-rails is loaded in your spec.

# Targets
expect(collection).to have(3).items
expect(collection).to have_exactly(3).items
expect(collection).to have_at_least(3).items
expect(collection).to have_at_most(3).items
collection.should have(3).items

# Assume `team` responds to #players.
expect(team).to have(3).players

# Assume #players is a private method.
expect(team).to have(3).players

# Converted
expect(collection.size).to eq(3)
expect(collection.size).to be >= 3
expect(collection.size).to be <= 3
collection.size.should == 3  # with `--keep should`

expect(team.players.size).to eq(3)

# have(n).items matcher invokes #players even if it's a private method.
expect(team.send(:players).size).to eq(3)

There's an option to continue using have(n).items matcher with rspec-collection_matchers that is a gem extracted from rspec-expectations. If you choose so, disable this conversion by either:

  • Specify --keep have_items option manually.
  • Require rspec-collection_matchers or rspec-rails in your spec so that Transpec automatically disables this conversion.

Note: rspec-rails 3.0 still uses have(n).items matcher with rspec-collection_matchers.

One-liner expectations with have(n).items matcher

This conversion will be disabled automatically if rspec-collection_matchers or rspec-rails is loaded in your spec.

# Targets
it { should have(3).items }
it { should have_at_least(3).players }

# Converted
it 'has 3 items' do
  expect(subject.size).to eq(3)
end

# With `--keep should`
it 'has 3 items' do
  subject.size.should == 3
end

it 'has at least 3 players' do
  expect(subject.players.size).to be >= 3
end
  • Conversion can be disabled by: --keep have_items

Expectations on block

# Targets
lambda { do_something }.should raise_error
proc { do_something }.should raise_error
-> { do_something }.should raise_error

# Converted
expect { do_something }.to raise_error

Negative error expectations with specific error

# Targets
expect { do_something }.not_to raise_error(SomeErrorClass)
expect { do_something }.not_to raise_error('message')
expect { do_something }.not_to raise_error(SomeErrorClass, 'message')
lambda { do_something }.should_not raise_error(SomeErrorClass)

# Converted
expect { do_something }.not_to raise_error
lambda { do_something }.should_not raise_error # with `--keep should`

Message expectations

# Targets
obj.should_receive(:foo)
Klass.any_instance.should_receive(:foo)

# Converted
expect(obj).to receive(:foo)
expect_any_instance_of(Klass).to receive(:foo)

Message expectations that are actually method stubs

# Targets
obj.should_receive(:foo).any_number_of_times
obj.should_receive(:foo).at_least(0)

Klass.any_instance.should_receive(:foo).any_number_of_times
Klass.any_instance.should_receive(:foo).at_least(0)

# Converted
allow(obj).to receive(:foo)
obj.stub(:foo) # with `--keep stub`

allow_any_instance_of(Klass).to receive(:foo)
Klass.any_instance.stub(:foo) # with `--keep stub`

Method stubs

# Targets
obj.stub(:foo)
obj.stub!(:foo)

obj.stub(:foo => 1, :bar => 2)

obj.stub_chain(:foo, :bar, :baz)

Klass.any_instance.stub(:foo)

# Converted
allow(obj).to receive(:foo)

# If the target project's rspec gem dependency is prior to 3.0.0.beta1
allow(obj).to receive(:foo).and_return(1)
allow(obj).to receive(:bar).and_return(2)

# If the target project's rspec gem dependency is 3.0.0.beta1 or later
allow(obj).to receive_messages(:foo => 1, :bar => 2)

# Conversion from `stub_chain` to `receive_message_chain` is available
# only if the target project's rspec gem dependency is 3.0.0.beta2 or later
allow(obj).to receive_message_chain(:foo, :bar, :baz)

allow_any_instance_of(Klass).to receive(:foo)

No replacement for unstub

There's no replacement for unstub in the expect syntax. See the discussion for more details.

Steps to upgrade obj.stub(:foo => 1, :bar => 2)

allow(obj).to receive_messages(:foo => 1, :bar => 2) that is designed to be the replacement for obj.stub(:foo => 1, :bar => 2) is available from RSpec 3.0 (though it's now being considered to be backported to RSpec 2.99). So, in the upgrade path to RSpec 3, if you want to convert them with keeping the syntax correspondence, you need to follow these steps:

  1. Upgrade to RSpec 2.99
  2. Run transpec --keep stub
  3. Upgrade to RSpec 3.0
  4. Run transpec

Otherwise obj.stub(:foo => 1, :bar => 2) will be converted to two allow(obj).to receive(...).and_return(...) expressions on RSpec 2.99.

Deprecated method stub aliases

# Targets
obj.stub!(:foo)
obj.unstub!(:foo)

# Converted
obj.stub(:foo) # with `--keep stub`
obj.unstub(:foo)

Method stubs with deprecated specification of number of times

# Targets
obj.stub(:foo).any_number_of_times
obj.stub(:foo).at_least(0)

# Converted
allow(obj).to receive(:foo)
obj.stub(:foo) # with `--keep stub`

Deprecated test double aliases

# Targets
stub('something')
mock('something')

# Converted
double('something')

Expectations on attribute of subject with its

This conversion will be disabled automatically if rspec-its is loaded in your spec.

# Targets
describe 'example' do
  subject { { foo: 1, bar: 2 } }
  its(:size) { should == 2 }
  its([:foo]) { should == 1 }
  its('keys.first') { should == :foo }
end

# Converted
describe 'example' do
  subject { { foo: 1, bar: 2 } }

  describe '#size' do
    subject { super().size }
    it { should == 2 }
  end

  describe '[:foo]' do
    subject { super()[:foo] }
    it { should == 1 }
  end

  describe '#keys' do
    subject { super().keys }
    describe '#first' do
      subject { super().first }
      it { should == :foo }
    end
  end
end

There's an option to continue using its with rspec-its that is a gem extracted from rspec-core. If you choose so, disable this conversion by either:

  • Specify --keep its option manually.
  • Require rspec-its in your spec so that Transpec automatically disables this conversion.

Current example object

This conversion is available only if your project has rspec gem dependency 2.99.0.beta1 or later.

# Targets
module ScreenshotHelper
  def save_failure_screenshot
    return unless example.exception
    # ...
  end
end

describe 'example page' do
  include ScreenshotHelper
  after { save_failure_screenshot }
  let(:user) { User.find(example.metadata[:user_id]) }
  # ...
end

# Converted
module ScreenshotHelper
  def save_failure_screenshot
    return unless RSpec.current_example.exception
    # ...
  end
end

describe 'example page' do
  include ScreenshotHelper
  after { save_failure_screenshot }
  let(:user) { |example| User.find(example.metadata[:user_id]) }
  # ...
end

Here's an excerpt from the warning for RSpec::Core::ExampleGroup#example and #running_example in RSpec 2.99:

RSpec::Core::ExampleGroup#example is deprecated and will be removed in RSpec 3. There are a few options for what you can use instead:

  • rspec-core's DSL methods (it, before, after, let, subject, etc) now yield the example as a block argument, and that is the recommended way to access the current example from those contexts.
  • The current example is now exposed via RSpec.current_example, which is accessible from any context.
  • If you can't update the code at this call site (e.g. because it is in an extension gem), you can use this snippet to continue making this method available in RSpec 2.99 and RSpec 3:
RSpec.configure do |c|
 c.expose_current_running_example_as :example
end

Compatibility

Tested on MRI 1.9, MRI 2.0 and JRuby in 1.9 mode.

Contributing

  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request

License

Copyright (c) 2013 Yuji Nakayama

See the LICENSE.txt for details.