```ruby
require './test/helper'

class ContentTypeDetectorTest < Test::Unit::TestCase
  context 'given a name' do
    should 'return a content type based on that name' do
      @filename = "/path/to/something.jpg"
      assert_equal "image/jpeg", Paperclip::ContentTypeDetector.new(@filename).detect
    end

    should 'return a content type based on the content of the file' do
      tempfile = Tempfile.new("something")
      tempfile.write("This is a file.")
      tempfile.rewind

      assert_equal "text/plain", Paperclip::ContentTypeDetector.new(tempfile.path).detect
    end

    should 'return an empty content type if the file is empty' do
      tempfile = Tempfile.new("something")
      tempfile.rewind

      assert_equal "inode/x-empty", Paperclip::ContentTypeDetector.new(tempfile.path).detect
    end

    should 'return a sensible default if no filename is supplied' do
      assert_equal "application/octet-stream", Paperclip::ContentTypeDetector.new('').detect
    end

    should 'return a sensible default if something goes wrong' do
      @filename = "/path/to/something"
      assert_equal "application/octet-stream", Paperclip::ContentTypeDetector.new(@filename).detect
    end

    should 'return a sensible default when the file command is missing' do
      Paperclip.stubs(:run).raises(Cocaine::CommandLineError.new)
      @filename = "/path/to/something"
      assert_equal "application/octet-stream", Paperclip::ContentTypeDetector.new(@filename).detect
    end
  end
end
```

Test the odd chance that returns nil
user
```ruby
require './test/helper'

class ContentTypeDetectorTest < Test::Unit::TestCase
  context 'given a name' do
    should 'return a content type based on that name' do
      @filename = "/path/to/something.jpg"
      assert_equal "image/jpeg", Paperclip::ContentTypeDetector.new(@filename).detect
    end

    should 'return a content type based on the content of the file' do
      tempfile = Tempfile.new("something")
      tempfile.write("This is a file.")
      tempfile.rewind

      assert_equal "text/plain", Paperclip::ContentTypeDetector.new(tempfile.path).detect
    end

    should 'return an empty content type if the file is empty' do
      tempfile = Tempfile.new("something")
      tempfile.rewind

      assert_equal "inode/x-empty", Paperclip::ContentTypeDetector.new(tempfile.path).detect
    end

    should 'return a sensible default if no filename is supplied' do
      assert_equal "application/octet-stream", Paperclip::ContentTypeDetector.new('').detect
    end

    should 'return a sensible default if something goes wrong' do
      @filename = "/path/to/something"
      assert_equal "application/octet-stream", Paperclip::ContentTypeDetector.new(@filename).detect
    end

    should 'return a sensible default when the file command is missing' do
      Paperclip.stubs(:run).raises(Cocaine::CommandLineError.new)
      @filename = "/path/to/something"
      assert_equal "application/octet-stream", Paperclip::ContentTypeDetector.new(@filename).detect
    end
  end

  should 'return a sensible default on the odd change that run returns nil' do
    Paperclip.stubs(:run).returns(nil)
    assert_equal "application/octet-stream",
                 Paperclip::ContentTypeDetector.new("windows").detect
  end
end
```
assistant