1 files changed, 23 insertions, 0 deletions
diff --git a/spec/ruby/library/stringio/binmode_spec.rb b/spec/ruby/library/stringio/binmode_spec.rb
new file mode 100644
index 0000000000..bc7ccda0a2
--- /dev/null
+++ b/spec/ruby/library/stringio/binmode_spec.rb
@@ -0,0 +1,23 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "StringIO#binmode" do
+  it "returns self" do
+    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