Rspec::BlockIsExpected

This gem does one very simple thing very well. It allows you to use block_is_expected similarly to how you would use is_expected if a block was wrapping the subject. Supports the same versions of Ruby that RSpec does, 1.8.7 - current ruby-head, as well as the JRuby equivalents.

subject { Integer(nil) }
it("raises") { block_is_expected.to(raise_error(TypeError)) }

Project	RSpec::BlockIsExpected
gem name	rspec-block_is_expected
license
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dependencies
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homepage	on Github.com, on Railsbling.com
documentation	on RDoc.info
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If you only ever want to test subjects wrapped in blocks, and are comfortable with losing the standard is_expected behavior, see an alternative to this gem here.

Add this line to your application's Gemfile:

gem "rspec-block_is_expected", :group => :test

And then execute:

$ bundle

Or install it yourself as:

$ gem install rspec-block_is_expected

There is no configuration needed if you your test suite loads the bundle group (e.g. test) that you added the gem to.

Otherwise, you may load it manually near the top of your spec_helper.rb, and it will self configure.

require "rspec/block_is_expected"

block_is_expected can be used to chain expectations related to the block, but to_not doesn't work with multiple expectations. So negated matchers are required. A basic set of them are included with this gem, and can be loaded with:

require "rspec/block_is_expected/matchers/not"

This gives you the following matchers:

RSpec::Matchers.define_negated_matcher(:not_change, :change)
RSpec::Matchers.define_negated_matcher(:not_include, :include)
RSpec::Matchers.define_negated_matcher(:not_eq, :eq)
RSpec::Matchers.define_negated_matcher(:not_raise_error, :raise_error)

You have a module like this:

module MyTasks
  def my_rakelib
    Rake.add_rakelib("bananas")
  end
  module_function :my_rakelib
end

You have a spec like this:

require "rake"

RSpec.describe(MyTasks) do
  describe "my_rakelib" do
    subject(:my_rakelib) { described_class.my_rakelib }
    it "updates rakelib" do
      block_is_expected.to(not_raise_error &
        change { Rake.application.options.rakelib }.from(["rakelib"]).to(%w[rakelib bananas]))
    end
  end
end

You'll likely get the following linting error from rubocop-rspec if you use block_is_expected.to ...:

RSpec/NoExpectationExample: No expectation found in this example.

To fix it properly you need to register block_is_expected as an "expectation". In your .rubocop.yml

inherit_gem:
  rspec-block_is_expected: rubocop.yml

The spec suite for this gem has some examples of usage, lightly edited here.

RSpec.describe("TestyMcTest") do
  context "errors raised" do
    subject { Integer(nil) }
    it("can be tested") do
      # Where you used to have:
      # expect { subject }.to raise_error(TypeError)
      block_is_expected.to(raise_error(TypeError))
    end
  end
  context "execution" do
    let(:mutex) { Mutex.new }
    subject { mutex.lock }
    it("can change state") do
      expect(mutex.locked?).to(eq(false))
      # Where you used to have:
      # expect { subject }.to_not raise_error
      block_is_expected.to_not(raise_error)
      expect(mutex.locked?).to(eq(true))
    end
  end
  context "changed state" do
    let(:mutex) { Mutex.new }
    subject { mutex.lock }
    it("can be tested") do
      # Where you used to have:
      # expect { subject }.to change { mutex.locked? }.from(false).to(true)
      block_is_expected.to(change { mutex.locked? }.from(false).to(true))
    end
  end
end

We recently migrated from master to main as the default branch. If this affected your local checkout:

git branch -m master main
git fetch origin
git branch -u origin/main main
git remote set-head origin -a

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 rubygems.org.

• Peter H. Boling of Rails Bling is the author.

See CONTRIBUTING.md. contributing: https://gitlab.com/pboling/rspec-block_is_expected/-/blob/main/CONTRIBUTING.md

See CONTRIBUTING.md. contributing: https://gitlab.com/pboling/rspec-stubbed_env/-/blob/main/CONTRIBUTING.md

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

This library aims to adhere to Semantic Versioning 2.0.0. Violations of this scheme should be reported as bugs. Specifically, if a minor or patch version is released that breaks backward compatibility, a new version should be immediately released that restores compatibility. Breaking changes to the public API will only be introduced with new major versions.

As a result of this policy, you can (and should) specify a dependency on this gem using the Pessimistic Version Constraint with two digits of precision.

For example in a Gemfile:

gem 'rspec-block_is_expected', '~> 1.0', group: [:development, :test]

or in a gemspec

spec.add_development_dependency 'rspec-block_is_expected', '~> 1.0'

• Copyright © 2018, 2020, 2023 Peter H. Boling of Rails Bling