1 files changed, 16 insertions, 2 deletions
diff --git a/spec/ruby/library/stringio/binmode_spec.rb b/spec/ruby/library/stringio/binmode_spec.rb
index 5d9a8c41df..bc7ccda0a2 100644
--- a/spec/ruby/library/stringio/binmode_spec.rb
+++ b/spec/ruby/library/stringio/binmode_spec.rb
@@ -3,7 +3,21 @@ require_relative 'fixtures/classes'
 
 describe "StringIO#binmode" do
   it "returns self" do
-    io = StringIO.new("example")
-    io.binmode.should equal(io)
+    io = StringIO.new(+"example")
+    io.binmode.should.equal?(io)
+  end
+
+  it "changes external encoding to BINARY" do
+    io = StringIO.new
+    io.external_encoding.should == Encoding.find('external')
+    io.binmode
+    io.external_encoding.should == Encoding::BINARY
+  end
+
+  it "does not set internal encoding" do
+    io = StringIO.new
+    io.internal_encoding.should == nil
+    io.binmode
+    io.internal_encoding.should == nil
   end
 end