Implicitly defined subject

If the first argument to an example group is a class, an instance of that class is exposed to each example in that example group 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.

subject exposed in top level group

Given a file named “toplevelsubject_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 “nestedsubjectspec.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 “nestedsubjectspec.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.