1 files changed, 21 insertions, 0 deletions
diff --git a/spec/rubyspec/library/stringio/external_encoding_spec.rb b/spec/rubyspec/library/stringio/external_encoding_spec.rb
new file mode 100644
index 0000000000..9bf2d8ee8c
--- /dev/null
+++ b/spec/rubyspec/library/stringio/external_encoding_spec.rb
@@ -0,0 +1,21 @@
+require 'stringio'
+require File.expand_path('../../../spec_helper', __FILE__)
+
+describe "StringIO#external_encoding" do
+  it "gets the encoding of the underlying String" do
+    io = StringIO.new
+    io.set_encoding Encoding::EUC_JP
+    io.external_encoding.should == Encoding::EUC_JP
+  end
+
+  ruby_version_is "2.3" do
+    it "does not set the encoding of its buffer string if the string is frozen" do
+      str = "foo".freeze
+      enc = str.encoding
+      io = StringIO.new(str)
+      io.set_encoding Encoding::EUC_JP
+      io.external_encoding.should == Encoding::EUC_JP
+      str.encoding.should == enc
+    end
+  end
+end