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Project: RSpec Core 3.1

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 (innermost wins)
`subject` exposed in top level group
Given
a file named "top_level_subject_spec.rb" with: 
RSpec.describe Array do
  it "should be empty when first created" do
    expect(subject).to 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: 
RSpec.describe Array do
  describe "when first created" do
    it "should be empty" do
      expect(subject).to 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 (innermost wins)
Given
a file named "nested_subject_spec.rb" with: 
class ArrayWithOneElement < Array
  def initialize(*)
    super
    unshift "first element"
  end
end

RSpec.describe Array do
  describe ArrayWithOneElement do
    context "referenced as subject" do
      it "contains one element" do
        expect(subject).to include("first element")
      end
    end
  end
end
When
I run rspec nested_subject_spec.rb
Then
the examples should all pass

Last published about 5 years ago by myronmarston.