diff --git a/core/method/fixtures/classes.rb b/core/method/fixtures/classes.rb
index f3b7ff921c..be96f65e25 100644
--- a/core/method/fixtures/classes.rb
+++ b/core/method/fixtures/classes.rb
@@ -50,6 +50,8 @@ def zero; end
     def one_req(a); end
     def two_req(a, b); end
 
+    def one_req_named(a:); end
+
     def zero_with_block(&blk); end
     def one_req_with_block(a, &blk); end
     def two_req_with_block(a, b, &blk); end
@@ -59,6 +61,8 @@ def one_req_one_opt(a, b=nil); end
     def one_req_two_opt(a, b=nil, c=nil); end
     def two_req_one_opt(a, b, c=nil); end
 
+    def one_opt_named(a: nil); end
+
     def one_opt_with_block(a=nil, &blk); end
     def one_req_one_opt_with_block(a, b=nil, &blk); end
     def one_req_two_opt_with_block(a, b=nil, c=nil, &blk); end
@@ -71,6 +75,8 @@ def one_req_one_opt_with_splat(a, b=nil, *c); end
     def two_req_one_opt_with_splat(a, b, c=nil, *d); end
     def one_req_two_opt_with_splat(a, b=nil, c=nil, *d); end
 
+    def zero_with_double_splat(**a); end
+
     def zero_with_splat_and_block(*a, &blk); end
     def one_req_with_splat_and_block(a, *b, &blk); end
     def two_req_with_splat_and_block(a, b, *c, &blk); end
diff --git a/core/method/shared/to_s.rb b/core/method/shared/to_s.rb
index 8f86745abe..4354e7b98b 100644
--- a/core/method/shared/to_s.rb
+++ b/core/method/shared/to_s.rb
@@ -26,8 +26,16 @@
 
   ruby_version_is "2.7" do
     it "returns a String containing method arguments" do
-      m = MethodSpecs::Methods.new.method :two_req
-      m.send(@method).should =~ /\#two_req\(a, b\)/
+      obj = MethodSpecs::Methods.new
+      obj.method(:zero).send(@method).should.include?("()")
+      obj.method(:one_req).send(@method).should.include?("(a)")
+      obj.method(:one_req_named).send(@method).should.include?("(a:)")
+      obj.method(:zero_with_block).send(@method).should.include?("(&blk)")
+      obj.method(:one_opt).send(@method).should.include?("(a=...)")
+      obj.method(:one_opt_named).send(@method).should.include?("(a: ...)")
+      obj.method(:zero_with_splat).send(@method).should.include?("(*a)")
+      obj.method(:zero_with_double_splat).send(@method).should.include?("(**a)")
+      obj.method(:one_req_one_opt_with_splat_and_block).send(@method).should.include?("(a, b=..., *c, &blk)")
     end
   end