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Project: RSpec Core 2.99

Publisher: RSpec

implicitly defined subject

If the first argument to the outermost example group is a class, an instance
of that class is exposed to each example via the subject method.

While the examples below demonstrate how subject can be used as a
user-facing concept, we recommend that you reserve it for support of custom
matchers and/or extension libraries that hide its use from examples.

Scenarios
  1. subject exposed in top level group
  2. subject in a nested group
  3. subject in a nested group with a different class (outermost wins)
subject exposed in top level group
Given
a file named "top_level_subject_spec.rb" with: 
describe Array do
  it "should be empty when first created" do
    subject.should be_empty
  end
end
When
I run rspec ./top_level_subject_spec.rb
Then
the examples should all pass
subject in a nested group
Given
a file named "nested_subject_spec.rb" with: 
describe Array do
  describe "when first created" do
    it "should be empty" do
      subject.should be_empty
    end
  end
end
When
I run rspec nested_subject_spec.rb
Then
the examples should all pass
subject in a nested group with a different class (outermost wins)
Given
a file named "nested_subject_spec.rb" with: 
class ArrayWithOneElement < Array
  def initialize(*)
    super
    unshift "first element"
  end
end

describe Array do
  describe ArrayWithOneElement do
    context "referenced as subject" do
      it "should be empty (because it is the Array declared at the top)" do
        subject.should be_empty
      end
    end

    context "created in the example" do
      it "should not be empty" do
        ArrayWithOneElement.new.should_not be_empty
      end
    end
  end
end
When
I run rspec nested_subject_spec.rb
Then
the examples should all pass

Last published almost 5 years ago by myronmarston.