Add args forwarding specs

language/args_forwaring_spec.rb

@@ -0,0 +1,37 @@
+require_relative '../spec_helper'
+
+ruby_version_is "2.7" do
+  describe "args forwarding def(...)" do
+    class F
+      def target(*args, **kwargs)
+        [args, kwargs]
+      end
+
+      def target_block(*args, **kwargs)
+        yield [kwargs, args]
+      end
+    end
+
+    it "delegates rest and kwargs" do
+      a = Class.new(F)
+      a.class_eval(<<-RUBY)
+        def delegate(...)
+          target(...)
+        end
+      RUBY
+
+      a.new.delegate(1, b: 2).should == [[1], {b: 2}]
+    end
+
+    it "delegates block" do
+      a = Class.new(F)
+      a.class_eval(<<-RUBY)
+        def delegate_block(...)
+          target_block(...)
+        end
+      RUBY
+
+      a.new.delegate_block(1, b: 2) { |x| x }.should == [{b: 2}, [1]]
+    end
+  end
+end