1 files changed, 47 insertions, 15 deletions
diff --git a/spec/ruby/core/string/uminus_spec.rb b/spec/ruby/core/string/uminus_spec.rb
index 53e73b7e67..43abf71d50 100644
--- a/spec/ruby/core/string/uminus_spec.rb
+++ b/spec/ruby/core/string/uminus_spec.rb
@@ -1,21 +1,53 @@
-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 self if the String is frozen' do
-      input  = 'foo'.freeze
-      output = -input
+describe 'String#-@' do
+  it 'returns self if the String is frozen' do
+    input  = 'foo'.freeze
+    output = -input
 
-      output.equal?(input).should == true
-      output.frozen?.should == true
-    end
+    output.should.equal?(input)
+    output.should.frozen?
+  end
+
+  it 'returns a frozen copy if the String is not frozen' do
+    input  = 'foo'
+    output = -input
+
+    output.should.frozen?
+    output.should_not.equal?(input)
+    output.should == 'foo'
+  end
+
+  it "returns the same object for equal unfrozen strings" do
+    origin = "this is a string"
+    dynamic = %w(this is a string).join(' ')
+
+    origin.should_not.equal?(dynamic)
+    (-origin).should.equal?(-dynamic)
+  end
+
+  it "returns the same object when it's called on the same String literal" do
+    (-"unfrozen string").should.equal?(-"unfrozen string")
+    (-"unfrozen string").should_not.equal?(-"another unfrozen string")
+  end
+
+  it "deduplicates frozen strings" do
+    dynamic = %w(this string is frozen).join(' ').freeze
+
+    dynamic.should_not.equal?("this string is frozen".freeze)
+
+    (-dynamic).should.equal?("this string is frozen".freeze)
+    (-dynamic).should.equal?((-"this string is frozen").freeze)
+  end
 
-    it 'returns a frozen copy if the String is not frozen' do
-      input  = 'foo'
-      output = -input
+  it "does not deduplicate a frozen string when it has instance variables" do
+    dynamic = %w(this string is frozen).join(' ')
+    dynamic.instance_variable_set(:@a, 1)
+    dynamic.freeze
 
-      output.frozen?.should == true
-      output.should == 'foo'
-    end
+    (-dynamic).should_not.equal?("this string is frozen".freeze)
+    (-dynamic).should_not.equal?((-"this string is frozen").freeze)
+    (-dynamic).should.equal?(-dynamic)
   end
 end