ftp.rb

    def fetch_data
      Net::FTP.open(host, username, password) do |ftp|
        begin
          ftp.binary = binary
          if file_name.is_a?(Regexp)
            files = ftp.nlst.select { |i| i =~ file_name }
            matching_file = files.pop
          end
          if file_newer && (@data_time = ftp.mtime(matching_file)) > file_newer
            @data = ftp.get(matching_file)
          end
        rescue Net::FTPError
          @error = ftp.last_response
        end
      end
    end

ftp_spec.rb

    it "connects given a hostname" do
      ftp = mock('ftp').as_null_object
      # ftp.should_receive(:login).with('uuu', 'ppp')
      # ftp.should_receive(:close).and_return nil
      Net::FTP.should_receive(:new).and_return(ftp)

      subject.get
    end

    it "connects given a hostname" do
      ftp = mock('ftp')
      # ftp.should_receive(:login).with('uuu', 'ppp')
      # ftp.should_receive(:close).and_return nil
      Net::FTP.should_receive(:open).and_yield(ftp)

      subject.get
    end

output.txt

  1) Importer::Providers::FTP#get connects given a hostname
     Failure/Error: Net::FTP.should_receive(:new).and_return(ftp)
       (<Net::FTP (class)>).new(any args)
           expected: 1 time
           received: 0 times
     # ./spec/lib/importer/providers/ftp_spec.rb:46:in `block (3 levels) in <top (required)>'



  1) Importer::Providers::FTP#get connects given a hostname
     Failure/Error: Net::FTP.should_receive(:open).and_yield(ftp)
       (<Net::FTP (class)>).open(any args)
           expected: 1 time
           received: 0 times
     # ./spec/lib/importer/providers/ftp_spec.rb:46:in `block (3 levels) in <top (required)>'