1 files changed, 47 insertions, 11 deletions
diff --git a/spec/ruby/core/string/uplus_spec.rb b/spec/ruby/core/string/uplus_spec.rb
index eafa721903..20767bcc01 100644
--- a/spec/ruby/core/string/uplus_spec.rb
+++ b/spec/ruby/core/string/uplus_spec.rb
@@ -1,24 +1,60 @@
-require File.expand_path('../../../spec_helper', __FILE__)
+# frozen_string_literal: false
+require_relative '../../spec_helper'
 
-ruby_version_is "2.3" do
-  describe 'String#+@' do
-    it 'returns an unfrozen copy of a frozen String' do
-      input  = 'foo'.freeze
-      output = +input
+describe 'String#+@' do
+  it 'returns an unfrozen copy of a frozen String' do
+    input  = 'foo'.freeze
+    output = +input
+
+    output.should_not.frozen?
+    output.should == 'foo'
+
+    output << 'bar'
+    output.should == 'foobar'
+  end
+
+  it 'returns a mutable String itself' do
+    input = String.new("foo")
+    output = +input
+
+    output.should.equal?(input)
+
+    input << "bar"
+    output.should == "foobar"
+  end
 
-      output.frozen?.should == false
-      output.should == 'foo'
+  context 'if file has "frozen_string_literal: true" magic comment' do
+    it 'returns mutable copy of a literal' do
+      ruby_exe(fixture(__FILE__, "freeze_magic_comment.rb")).should == 'mutable'
     end
+  end
 
-    it 'returns self if the String is not frozen' do
+  context 'if file has "frozen_string_literal: false" magic comment' do
+    it 'returns literal string itself' do
       input  = 'foo'
       output = +input
 
       output.equal?(input).should == true
     end
+  end
 
-    it 'returns mutable copy despite freeze-magic-comment in file' do
-      ruby_exe(fixture(__FILE__, "freeze_magic_comment.rb")).should == 'mutable'
+  context 'if file has no frozen_string_literal magic comment' do
+    ruby_version_is ''...'3.4' do
+      it 'returns literal string itself' do
+        eval(<<~RUBY).should == true
+          s = "foo"
+          s.equal?(+s)
+        RUBY
+      end
+    end
+
+    ruby_version_is '3.4' do
+      it 'returns mutable copy of a literal' do
+        eval(<<~RUBY).should == false
+          s = "foo"
+          s.equal?(+s)
+        RUBY
+      end
     end
   end
 end