```ruby
require File.dirname(__FILE__) + '/../../../spec_helper'
require 'stringio'
require 'zlib'

describe "GzipWriter#write" do

  before :each do
    @data = '12345abcde'
    @zip = "\037\213\b\000,\334\321G\000\00334261MLJNI\005\000\235\005\000$\n\000\000\000"
    @io = StringIO.new
  end

  it "writes some compressed data" do
    Zlib::GzipWriter.wrap @io do |gzio|
      gzio.write @data
    end

    # skip gzip header for now
    @io.string[10..-1].should == @zip[10..-1]
  end

end

```

Add magic comment and give initial string to set its encoding.
user
```ruby
#coding:ASCII-8BIT
require File.dirname(__FILE__) + '/../../../spec_helper'
require 'stringio'
require 'zlib'

describe "GzipWriter#write" do

  before :each do
    @data = '12345abcde'
    @zip = "\037\213\b\000,\334\321G\000\00334261MLJNI\005\000\235\005\000$\n\000\000\000"
    @io = StringIO.new('')
  end

  it "writes some compressed data" do
    Zlib::GzipWriter.wrap @io do |gzio|
      gzio.write @data
    end

    # skip gzip header for now
    @io.string[10..-1].should == @zip[10..-1]
  end

end

```
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