Add new RSpec/MultipleTestTargetsPerSpecFile cop

.rubocop.yml

@@ -153,6 +153,8 @@ RSpec/IndexedLet:
   Enabled: true
 RSpec/MatchArray:
   Enabled: true
+RSpec/MultipleTestTargetsPerSpecFile:
+  Enabled: true
 RSpec/NoExpectationExample:
   Enabled: true
 RSpec/PendingWithoutReason:

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Master (Unreleased)
 
 - Fix an infinite loop error when `RSpec/ExcessiveDocstringSpacing` finds a description with non-ASCII leading/trailing whitespace. ([@bcgraham])
+- Add new `RSpec/MultipleTestTargetsPerSpecFile` cop. ([@ydah])
 
 ## 2.23.2 (2023-08-09)
 

config/default.yml

@@ -649,6 +649,12 @@ RSpec/MultipleSubjects:
   VersionAdded: '1.16'
   Reference: https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/MultipleSubjects
 
+RSpec/MultipleTestTargetsPerSpecFile:
+  Description: Checks that spec files only include one test target object.
+  Enabled: pending
+  VersionAdded: "<<next>>"
+  Reference: https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/MultipleTestTargetsPerSpecFile
+
 RSpec/NamedSubject:
   Description: Checks for explicitly referenced test subjects.
   Enabled: true

lib/rubocop/cop/rspec/multiple_test_targets_per_spec_file.rb

@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module RSpec
+      # Checks that spec files only include one test target object.
+      #
+      # @example
+      #   # bad
+      #   RSpec.describe User do
+      #     # ...
+      #     decribe User::Admin do
+      #       # ...
+      #     end
+      #   end
+      #
+      #   # bad
+      #   RSpec.describe User do
+      #     # ...
+      #   end
+      #   RSpec.describe Admin do
+      #     # ...
+      #   end
+      #
+      #   # good
+      #   RSpec.describe User do
+      #     # ...
+      #   end
+      #
+      class MultipleTestTargetsPerSpecFile < Base
+        MSG = 'Spec files should only include one test target object.'
+
+        # @!method describe_classes(node)
+        def_node_search :describe_classes, <<~PATTERN
+          (block $(send #rspec? #ExampleGroups.all (const ...) ...) ...)
+        PATTERN
+
+        def on_investigation_end
+          return unless processed_source.ast
+
+          describes = describe_classes(processed_source.ast)
+          return if describes.count <= 1
+
+          describes.each do |node|
+            add_offense(node)
+          end
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/rspec_cops.rb

@@ -91,6 +91,7 @@
 require_relative 'rspec/multiple_expectations'
 require_relative 'rspec/multiple_memoized_helpers'
 require_relative 'rspec/multiple_subjects'
+require_relative 'rspec/multiple_test_targets_per_spec_file'
 require_relative 'rspec/named_subject'
 require_relative 'rspec/nested_groups'
 require_relative 'rspec/no_expectation_example'

spec/rubocop/cop/rspec/multiple_test_targets_per_spec_file_spec.rb

@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::RSpec::MultipleTestTargetsPerSpecFile, :config do
+  it 'registers an offense when include a class and a nested class describe' do
+    expect_offense(<<~RUBY)
+      RSpec.describe User do
+      ^^^^^^^^^^^^^^^^^^^ Spec files should only include one test target object.
+        # ...
+        describe User::Admin do
+        ^^^^^^^^^^^^^^^^^^^^ Spec files should only include one test target object.
+          # ...
+        end
+
+        describe User::Moderator do
+        ^^^^^^^^^^^^^^^^^^^^^^^^ Spec files should only include one test target object.
+          # ...
+        end
+      end
+    RUBY
+  end
+
+  it 'registers an offense when include multiple classes' do
+    expect_offense(<<~RUBY)
+      RSpec.describe User do
+      ^^^^^^^^^^^^^^^^^^^ Spec files should only include one test target object.
+        # ...
+      end
+
+      RSpec.describe Admin do
+      ^^^^^^^^^^^^^^^^^^^^ Spec files should only include one test target object.
+        # ...
+      end
+    RUBY
+  end
+
+  it 'does not register an offense when include only class' do
+    expect_no_offenses(<<~RUBY)
+      RSpec.describe User do
+        describe '#method' do
+          # ...
+        end
+      end
+    RUBY
+  end
+end