Add RSpec/NoExpectationExample

In response to the review comments, I added the following changes later:

- Prefer x_type? to is_a?
- Use RSpec.Language.Examples
- Add are_expected to expectation method names
- Prefer on_block to on_send
- Add more methods to RSpec.Language.Expectations
- Use RSpec.Language.Expectations
- Replace with clearer custom method names
- Add some missing \@return comments

.rubocop.yml

@@ -72,6 +72,13 @@ Naming/InclusiveLanguage:
       Suggestions:
         - offense
 
+RSpec:
+  Language:
+    Expectations:
+      - expect_correction
+      - expect_no_offenses
+      - expect_offense
+
 RSpec/ExampleLength:
   CountAsOne:
     - heredoc
@@ -81,6 +88,12 @@ RSpec/DescribeClass:
   Exclude:
     - spec/project/**/*.rb
 
+RSpec/MultipleExpectations:
+  Max: 2
+
+RSpec/NoExpectationExample:
+  Enabled: true
+
 Style/FormatStringToken:
   Exclude:
     - spec/rubocop/**/*.rb

CHANGELOG.md

@@ -5,6 +5,7 @@
 * Fix `RSpec/FilePath` cop missing mismatched expanded namespace. ([@sl4vr][])
 * Add new `AllowConsecutiveOneLiners` (default true) option for `Rspec/EmptyLineAfterHook` cop. ([@ngouy][])
 * Add autocorrect support for `RSpec/EmptyExampleGroup`. ([@r7kamura][])
+* Add `RSpec/NoExpectationExample`. ([@r7kamura][])
 
 ## 2.12.1 (2022-07-03)
 

config/default.yml

@@ -61,9 +61,14 @@ RSpec:
       Pending:
         - pending
     Expectations:
+      - are_expected
       - expect
-      - is_expected
       - expect_any_instance_of
+      - is_expected
+      - should
+      - should_not
+      - should_not_receive
+      - should_receive
     Helpers:
       - let
       - let!
@@ -614,6 +619,13 @@ RSpec/NestedGroups:
   VersionChanged: '1.10'
   Reference: https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/NestedGroups
 
+RSpec/NoExpectationExample:
+  Description: Checks if an example includes any expectation.
+  Enabled: pending
+  Safe: false
+  VersionAdded: '2.13'
+  Reference: https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/NoExpectationExample
+
 RSpec/NotToNot:
   Description: Checks for consistent method usage for negating expectations.
   Enabled: true

docs/modules/ROOT/pages/cops.adoc

@@ -61,6 +61,7 @@
 * xref:cops_rspec.adoc#rspecmultiplesubjects[RSpec/MultipleSubjects]
 * xref:cops_rspec.adoc#rspecnamedsubject[RSpec/NamedSubject]
 * xref:cops_rspec.adoc#rspecnestedgroups[RSpec/NestedGroups]
+* xref:cops_rspec.adoc#rspecnoexpectationexample[RSpec/NoExpectationExample]
 * xref:cops_rspec.adoc#rspecnottonot[RSpec/NotToNot]
 * xref:cops_rspec.adoc#rspecoverwritingsetup[RSpec/OverwritingSetup]
 * xref:cops_rspec.adoc#rspecpending[RSpec/Pending]

docs/modules/ROOT/pages/cops_rspec.adoc

@@ -3284,6 +3284,51 @@ end
 
 * https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/NestedGroups
 
+== RSpec/NoExpectationExample
+
+|===
+| Enabled by default | Safe | Supports autocorrection | Version Added | Version Changed
+
+| Pending
+| No
+| Yes (Unsafe)
+| 2.13
+| -
+|===
+
+Checks if an example includes any expectation.
+
+All RSpec's example and expectation methods are covered by default.
+If you are using your own custom methods,
+add the following configuration:
+
+  RSpec:
+    Language:
+      Examples:
+        Regular:
+          - custom_it
+      Expectations:
+        - custom_expect
+
+=== Examples
+
+[source,ruby]
+----
+# bad
+it do
+  a?
+end
+
+# good
+it do
+  expect(a?).to be(true)
+end
+----
+
+=== References
+
+* https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/NoExpectationExample
+
 == RSpec/NotToNot
 
 |===

lib/rubocop/cop/rspec/no_expectation_example.rb

@@ -0,0 +1,90 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module RSpec
+      # Checks if an example includes any expectation.
+      #
+      # All RSpec's example and expectation methods are covered by default.
+      # If you are using your own custom methods,
+      # add the following configuration:
+      #
+      #   RSpec:
+      #     Language:
+      #       Examples:
+      #         Regular:
+      #           - custom_it
+      #       Expectations:
+      #         - custom_expect
+      #
+      # @example
+      #
+      #   # bad
+      #   it do
+      #     a?
+      #   end
+      #
+      #   # good
+      #   it do
+      #     expect(a?).to be(true)
+      #   end
+      class NoExpectationExample < Base
+        extend AutoCorrector
+
+        include RangeHelp
+
+        MSG = 'No expectation found in this example.'
+
+        # @!method expectation_method_call?(node)
+        # @param [RuboCop::AST::Node] node
+        # @return [Boolean]
+        def_node_matcher(
+          :expectation_method_call?,
+          send_pattern('#Expectations.all')
+        )
+
+        # @param [RuboCop::AST::BlockNode] node
+        def on_block(node)
+          return unless example_method_call?(node)
+          return if including_any_expectation?(node)
+
+          add_offense(node) do |corrector|
+            corrector.remove(removed_range(node))
+          end
+        end
+
+        private
+
+        # @param [RuboCop::AST::BlockNode] node
+        # @return [Boolean]
+        def example_method_call?(node)
+          Examples.all(node.method_name)
+        end
+
+        # Recursively checks if the given node includes any expectation.
+        # @param [RuboCop::AST::Node] node
+        # @return [Boolean]
+        def including_any_expectation?(node)
+          if !node.is_a?(::RuboCop::AST::Node)
+            false
+          elsif expectation_method_call?(node)
+            true
+          else
+            node.children.any? do |child|
+              including_any_expectation?(child)
+            end
+          end
+        end
+
+        # @param [RuboCop::AST::Node] node
+        # @return [Parser::Source::Range]
+        def removed_range(node)
+          range_by_whole_lines(
+            node.location.expression,
+            include_final_newline: true
+          )
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/rspec_cops.rb

@@ -77,6 +77,7 @@
 require_relative 'rspec/multiple_subjects'
 require_relative 'rspec/named_subject'
 require_relative 'rspec/nested_groups'
+require_relative 'rspec/no_expectation_example'
 require_relative 'rspec/not_to_not'
 require_relative 'rspec/overwriting_setup'
 require_relative 'rspec/pending'

spec/rubocop/cop/rspec/no_expectation_example_spec.rb

@@ -0,0 +1,120 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::RSpec::NoExpectationExample do
+  context 'with empty example with it' do
+    it 'registers an offense' do
+      expect_offense(<<~RUBY)
+        RSpec.describe Foo do
+          it { bar }
+          ^^^^^^^^^^ No expectation found in this example.
+
+          it { expect(baz).to be_truthy }
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        RSpec.describe Foo do
+
+          it { expect(baz).to be_truthy }
+        end
+      RUBY
+    end
+  end
+
+  context 'with empty example with specify' do
+    it 'registers an offense' do
+      expect_offense(<<~RUBY)
+        specify { bar }
+        ^^^^^^^^^^^^^^^ No expectation found in this example.
+      RUBY
+
+      expect_correction(<<~RUBY)
+      RUBY
+    end
+  end
+
+  context 'with non-empty example with should' do
+    it 'registers no offenses' do
+      expect_no_offenses(<<~RUBY)
+        it { should be_truthy }
+      RUBY
+    end
+  end
+
+  context 'with empty examples' do
+    it 'registers offenses' do
+      expect_offense(<<~RUBY)
+        it { bar }
+        ^^^^^^^^^^ No expectation found in this example.
+        it { baz }
+        ^^^^^^^^^^ No expectation found in this example.
+      RUBY
+
+      expect_correction(<<~RUBY)
+      RUBY
+    end
+  end
+
+  context 'with non-empty example with custom expectation' do
+    it 'registers an offense' do
+      expect_offense(<<~RUBY)
+        it { custom_expect(bar) }
+        ^^^^^^^^^^^^^^^^^^^^^^^^^ No expectation found in this example.
+      RUBY
+
+      expect_correction(<<~RUBY)
+      RUBY
+    end
+  end
+
+  context 'with non-empty example with configured custom expectation' do
+    before do
+      other_cops.dig('RSpec', 'Language', 'Expectations').push('custom_expect')
+    end
+
+    it 'registers no offenses' do
+      expect_no_offenses(<<~RUBY)
+        it { custom_expect(bar) }
+      RUBY
+    end
+  end
+
+  context 'with empty example with custom example method' do
+    it 'registers no offenses' do
+      expect_no_offenses(<<~RUBY)
+        custom_it { foo }
+      RUBY
+    end
+  end
+
+  context 'with empty example with configured custom example method' do
+    before do
+      other_cops.dig(
+        'RSpec',
+        'Language',
+        'Examples',
+        'Regular'
+      ).push('custom_it')
+    end
+
+    it 'registers an offense' do
+      expect_offense(<<~RUBY)
+        custom_it { foo }
+        ^^^^^^^^^^^^^^^^^ No expectation found in this example.
+      RUBY
+
+      expect_correction(<<~RUBY)
+      RUBY
+    end
+  end
+
+  context 'with block-less example in block' do
+    it 'registers no offenses' do
+      expect_no_offenses(<<~RUBY)
+        RSpec.describe Foo do
+          pending 'not implemented'
+        end
+      RUBY
+    end
+  end
+end