Add special case for Class.new method signature that should use initialize signature instead

lib/rspec/support/method_signature_verifier.rb

@@ -12,7 +12,7 @@ class MethodSignature # rubocop:disable ClassLength
       attr_reader :min_non_kw_args, :max_non_kw_args, :optional_kw_args, :required_kw_args
 
       def initialize(method)
-        @method           = method
+        @method           = method_or_class_initialize(method)
         @optional_kw_args = []
         @required_kw_args = []
         classify_parameters
@@ -158,6 +158,15 @@ def unlimited_args?
       end
 
       INFINITY = 1 / 0.0
+
+      private
+
+      def method_or_class_initialize(method)
+        return method if method.is_a? Proc # included shared examples
+        # Special treatment for stubbing `Class.new`
+        return method unless method.owner == Class && method.name == :new
+        method.receiver.instance_method(:initialize)
+      end
     end
 
     if RSpec::Support::Ruby.jruby?

spec/rspec/support/method_signature_verifier_spec.rb

@@ -817,6 +817,63 @@ def arity_block(_, &block); end
           end
         end
 
+        describe 'an `.new` method' do
+          old_verbose, $VERBOSE = $VERBOSE, false
+          class TestInitializeClass; def initialize(arg1, arg2); end; end
+          class TestNewClass; def self.new(arg1, arg2, arg3); super; end; end
+          $VERBOSE = old_verbose
+
+          describe 'for pure Class' do
+            let(:test_method) { Class.method(:new) }
+
+            it 'match unlimited arguments' do
+              expect(validate_expectation :unlimited_args).to eq(true)
+            end
+
+            it 'validates against 2 arguments' do
+              expect(valid_non_kw_args?(2)).to eq true
+            end
+
+            it 'validates against 2 arguments' do
+              expect(valid_non_kw_args?(3)).to eq true
+            end
+          end
+
+          describe 'for class with initialize method' do
+
+
+            let(:test_method) { TestInitializeClass.method(:new) }
+
+            it 'does not match unlimited arguments' do
+              expect(validate_expectation :unlimited_args).to eq(false)
+            end
+
+            it 'validates against 2 arguments' do
+              expect(valid_non_kw_args?(2)).to eq true
+            end
+
+            it 'fails validation against 3 arguments' do
+              expect(valid_non_kw_args?(3)).to eq false
+            end
+          end
+
+          describe 'for class with owerwritten new method' do
+            let(:test_method) { TestNewClass.method(:new) }
+
+            it 'does not match unlimited arguments' do
+              expect(validate_expectation :unlimited_args).to eq(false)
+            end
+
+            it 'fails validation against 2 arguments' do
+              expect(valid_non_kw_args?(2)).to eq false
+            end
+
+            it 'validates against 3 arguments' do
+              expect(valid_non_kw_args?(3)).to eq true
+            end
+          end
+        end
+
         if Ruby.jruby?
           describe 'a single-argument Java method' do
             let(:test_method) { Java::JavaLang::String.instance_method(:char_at) }