Implement Deferred::Provider.defined_deferred_examples?

README.md

@@ -1154,7 +1154,24 @@ RSpec.describe Car do
 end
 ```
 
-Finally, `Deferred::Consumer` includes the shortcuts `#finclude_deferred` and `#fwrap_deferred` to automatically focus deferred examples, or `#xinclude_deferred` and `#xwrap_deferred` to skip deferred examples.
+`Deferred::Consumer` also includes the shortcuts `#finclude_deferred` and `#fwrap_deferred` to automatically focus deferred examples, or `#xinclude_deferred` and `#xwrap_deferred` to skip deferred examples.
+
+The `defined_deferred_examples?` and `defined_deferred_context?` methods allow checking for the presence of a deferred example group.
+
+```ruby
+RSpec.describe Boat do
+  include RSpec::SleepingKingStudios::Deferred::Consumer
+  include VehicleExamples
+
+  subject(:boat) { described_class.new }
+
+  if defined_deferred_examples?('should be a water Vehicle')
+    include_deferred 'should be a water Vehicle'
+  else
+    pending 'deferred examples "should be a water Vehicle" is not defined'
+  end
+end
+```
 
 ## Shared Examples
 

lib/rspec/sleeping_king_studios/deferred/provider.rb

@@ -55,6 +55,22 @@ def defined_deferred_examples
         @defined_deferred_examples ||= {}
       end
 
+      # Checks if the given deferred example group is defined.
+      #
+      # @param description [String] the name of the deferred examples.
+      #
+      # @return [true, false] true if a deferred example group with the given
+      #   description is defined in the current context; otherwise false.
+      def defined_deferred_examples?(description)
+        ancestors.any? do |ancestor|
+          next false unless ancestor.respond_to?(:defined_deferred_examples)
+
+          ancestor.deferred_definition_exists?(description) ||
+            ancestor.deferred_module_exists?(description)
+        end
+      end
+      alias defined_deferred_context? defined_deferred_examples?
+
       # @api private
       def find_deferred_examples(description)
         tools.assertions.validate_name(description, as: 'description')
@@ -72,6 +88,21 @@ def find_deferred_examples(description)
 
       protected
 
+      def deferred_definition_exists?(description)
+        defined_deferred_examples.key?(description)
+      end
+
+      def deferred_module_exists?(description)
+        constants(false)
+          .any? do |const_name|
+            value = const_get(const_name)
+
+            next false unless module_is_deferred_examples?(value)
+
+            return true if matches_description?(description, const_name, value)
+          end
+      end
+
       def find_deferred_definition(description)
         defined_deferred_examples.fetch(description, nil)
       end

spec/rspec/sleeping_king_studios/deferred/provider_spec.rb

@@ -7,6 +7,7 @@
 
 RSpec.describe RSpec::SleepingKingStudios::Deferred::Provider do
   extend RSpec::SleepingKingStudios::Concerns::ExampleConstants
+  include RSpec::SleepingKingStudios::Matchers::Macros
   include Spec::Support::SharedExamples::DeferredRegistryExamples
 
   subject(:registry) { described_class }

spec/support/shared_examples/deferred_registry_examples.rb

@@ -1,12 +1,14 @@
 # frozen_string_literal: true
 
 require 'rspec/sleeping_king_studios/concerns/shared_example_group'
+require 'rspec/sleeping_king_studios/matchers/core/have_aliased_method'
 
 require 'support/shared_examples'
 
 module Spec::Support::SharedExamples
   module DeferredRegistryExamples
-    extend RSpec::SleepingKingStudios::Concerns::SharedExampleGroup
+    extend  RSpec::SleepingKingStudios::Concerns::SharedExampleGroup
+    include RSpec::SleepingKingStudios::Matchers::Macros
 
     shared_context 'when the parent registry has deferred examples' do
       let(:ancestor_deferred_examples) do
@@ -203,6 +205,91 @@ module DeferredRegistryExamples
         end
       end
 
+      describe '.defined_deferred_examples?' do
+        it 'should define the class method' do
+          expect(described_class)
+            .to respond_to(:defined_deferred_examples?)
+            .with(1).argument
+        end
+
+        it 'should alias the method' do
+          expect(described_class)
+            .to have_aliased_method(:defined_deferred_examples?)
+            .as(:defined_deferred_context?)
+        end
+
+        describe 'with a non-matching description' do
+          let(:description) { 'should do nothing' }
+
+          it 'should return false' do
+            expect(described_class.defined_deferred_examples?(description))
+              .to be false
+          end
+        end
+
+        context 'when the parent registry has deferred examples' do
+          include_context 'when the parent registry has deferred examples'
+
+          describe 'with a non-matching description' do
+            let(:description) { 'should do nothing' }
+
+            it 'should return false' do
+              expect(described_class.defined_deferred_examples?(description))
+                .to be false
+            end
+          end
+
+          describe 'with a description matching a definition' do
+            let(:description) { 'should do a thing' }
+
+            it 'should return true' do
+              expect(described_class.defined_deferred_examples?(description))
+                .to be true
+            end
+          end
+
+          describe 'with a description matching a module' do
+            let(:description) { 'should behave like a BasicObject' }
+
+            it 'should return true' do
+              expect(described_class.defined_deferred_examples?(description))
+                .to be true
+            end
+          end
+        end
+
+        context 'when the registry has deferred examples' do
+          include_context 'when the registry has deferred examples'
+
+          describe 'with a non-matching description' do
+            let(:description) { 'should do nothing' }
+
+            it 'should return false' do
+              expect(described_class.defined_deferred_examples?(description))
+                .to be false
+            end
+          end
+
+          describe 'with a description matching a definition' do
+            let(:description) { 'should do something' }
+
+            it 'should return true' do
+              expect(described_class.defined_deferred_examples?(description))
+                .to be true
+            end
+          end
+
+          describe 'with a description matching a module' do
+            let(:description) { 'should act as expected' }
+
+            it 'should return true' do
+              expect(described_class.defined_deferred_examples?(description))
+                .to be true
+            end
+          end
+        end
+      end
+
       describe '.find_deferred_examples' do
         it 'should define the class method' do
           expect(described_class)