1 files changed, 16 insertions, 5 deletions
diff --git a/spec/ruby/core/io/write_nonblock_spec.rb b/spec/ruby/core/io/write_nonblock_spec.rb
index a8b9ce0a36..a6bd43c058 100644
--- a/spec/ruby/core/io/write_nonblock_spec.rb
+++ b/spec/ruby/core/io/write_nonblock_spec.rb
@@ -31,15 +31,26 @@ platform_is_not :windows do
       end
     end
 
+    it "does not modify the passed argument" do
+      File.open(@filename, "w") do |f|
+        f.set_encoding(Encoding::IBM437)
+        # A character whose codepoint differs between UTF-8 and IBM437
+        f.write_nonblock("ƒ".freeze)
+      end
+
+      File.binread(@filename).bytes.should == [198, 146]
+    end
+
     it "checks if the file is writable if writing zero bytes" do
       -> {
-         @readonly_file.write_nonblock("")
-      }.should raise_error(IOError)
+        @readonly_file.write_nonblock("")
+      }.should.raise(IOError)
     end
   end
 
   describe "IO#write_nonblock" do
     it_behaves_like :io_write, :write_nonblock
+    it_behaves_like :io_write_no_transcode, :write_nonblock
   end
 end
 
@@ -56,12 +67,12 @@ describe 'IO#write_nonblock' do
   it "raises an exception extending IO::WaitWritable when the write would block" do
     -> {
       loop { @write.write_nonblock('a' * 10_000) }
-    }.should raise_error(IO::WaitWritable) { |e|
+    }.should.raise(IO::WaitWritable) { |e|
       platform_is_not :windows do
-        e.should be_kind_of(Errno::EAGAIN)
+        e.should.is_a?(Errno::EAGAIN)
       end
       platform_is :windows do
-        e.should be_kind_of(Errno::EWOULDBLOCK)
+        e.should.is_a?(Errno::EWOULDBLOCK)
       end
     }
   end