diff --git a/bin/csv-filter b/bin/csv-filter
new file mode 100644
index 00000000..84a8baf6
--- /dev/null
+++ b/bin/csv-filter
@@ -0,0 +1,234 @@
+#!/usr/bin/env ruby
+
+require 'optparse'
+require 'csv'
+
+# Returns an array of names.
+# \String +s+ contains a comma-separated list of names.
+def parse_names(s)
+  s.split(",").collect(&:to_sym)
+end
+
+options = {}
+
+parser = OptionParser.new
+
+parser.version = CSV::VERSION
+parser.banner = <<-BANNER
+Usage: #{parser.program_name} [options]
+
+  Reads and parses the CSV text content of the standard input per the given input options.
+  From that content, generates CSV text per the given output options and writes
+  that text to the standard output.
+
+  Three options are similar for input and output:
+
+  - Row separator:
+  
+    - The input row separator is determined:
+  
+      - By option --input-row-sep, if given.
+      - Otherwise, by option --row-sep, if given.
+      - Otherwise, by auto-discovery.
+  
+    - The output row separator is determined:
+  
+      - By option --output-row-sep if given.
+      - Otherwise, by option --row-sep if given.
+      - Otherwise, as the newline character ("\\n").
+  
+  - Column separator:
+  
+    - The input column separator is determined:
+  
+      - By option --input-col-sep, if given.
+      - Otherwise, by option --col-sep, if given.
+      - Otherwise, as the comma character (",").
+  
+    - The output column separator is determined:
+  
+      - By option --output-col-sep if given.
+      - Otherwise, by option --col-sep if given.
+      - Otherwise, as the comma character (",").
+  
+  - Quote character:
+  
+    - The input quote character is determined:
+  
+      - By option --input-quote-char, if given.
+      - Otherwise, by option --quote-char, if given.
+      - Otherwise, as the double-quote character ('"').
+  
+    - The output quote character is determined:
+  
+      - By option --output-quote-char, if given.
+      - Otherwise, by option --quote-char, if given.
+      - Otherwise, as the double-quote character ('"').
+BANNER
+
+parser.separator(nil)
+parser.separator(
+  'Input Options: see https://docs.ruby-lang.org/en/3.3/CSV.html#class-CSV-label-Options+for+Parsing'
+)
+
+parser.separator(nil)
+parser.on('--converters=CONVERTERS',
+     'Input field converters;',
+     'CONVERTERS is comma-separated converter names (leading colon optional).'
+) do |value|
+  options[:converters] = parse_names(value)
+end
+# parser.on('--empty_value STR',
+#      'Value to be output for empty input field.') do |value|
+#   options[:empty_value] = value
+# end
+parser.on('--field-size-limit=N', Integer,
+     'Maximum field size (characters)') do |value|
+  options[:field_size_limit] = value
+end
+parser.on('--headers=ARG',
+     'Treat the first input row as headers;',
+     'ARG is true or comma-separated headers.'
+) do |value|
+  options[:headers] = value == 'true' ? true : parse_names(value)
+end
+parser.on('--header-converters=CONVERTERS',
+     'Input header converters;',
+     'CONVERTERS is comma-separated converter names.'
+) do |value|
+  options[:header_converters] = parse_names(value)
+end
+parser.on('--liberal-parsing',
+     'Attempt to parse non-conformant input.') do
+  options[:liberal_parsing] = :no_argument
+end
+# parser.on('--nil_value STR',
+#      'Value to be substituted for nil input field.') do |value|
+#   options[:nil_value] = value
+# end
+# parser.on('--return_headers',
+#      'Method shift returns header row.') do
+#   options[:return_headers] = :no_argument
+# end
+# parser.on('--skip_blanks',
+#      'Ignore blank lines.') do
+#   options[:skip_blanks] = :no_argument
+# end
+# parser.on('--skip_lines STR',
+#      'Ignore comment lines;',
+#      'STR is converted to a Regexp that identifies comment lines.') do |value|
+#   options[:skip_lines] = Regexp.new(value)
+# end
+# parser.on('--strip',
+#      'Strip whitespace from input fields.') do
+#   options[:strip] = :no_argument
+# end
+# parser.on('--unconverted_fields',
+#      'Define method unconverted_fields for each created CSV::Row object.') do
+#   options[:unconverted_fields] = :no_argument
+# end
+
+parser.separator(nil)
+parser.separator(
+  'Output Options: see https://docs.ruby-lang.org/en/3.3/CSV.html#class-CSV-label-Options+for+Generating'
+)
+
+parser.separator(nil)
+# parser.on('--force_quotes',
+#      'Double-quote each output field.') do
+#   options[:force_quotes] = :no_argument
+# end
+# parser.on('--quote_empty STR',
+#      'Double-quote each empty output field;',
+#      'STR is true or false.'
+# ) do
+#   options[:quote_empty] = :no_argument
+# end
+# parser.on('--write_converters',
+#      'Output field converters;',
+#      'not implemented in CLI.'
+# ) do |value|
+#   raise NotImplementedError.new('--write_converters is not implemented in the CLI.')
+# end
+# parser.on('--write_headers',
+#      'Write headers to output.') do |value|
+#   options[:write_headers] = :no_argument
+# end
+# parser.on('--write_empty_value STR',
+#      'Value to be substituted for empty output field.') do |value|
+#   options[:write_empty_value] = value
+# end
+# parser.on('--write_nil_value STR',
+#      'Value to be substituted for nil output field.') do |value|
+#   options[:write_nil_value] = value
+# end
+
+parser.separator(nil)
+parser.separator(
+  'Options only for CSV.filter: see https://docs.ruby-lang.org/en/3.3/CSV.html#method-c-filter'
+)
+
+parser.on('--input-col-sep=SEPARATOR',
+     'Input column separator string (aliased as --in-col-sep).') do |value|
+  options[:input_col_sep] = value
+end
+parser.on('--input-quote-char=CHAR',
+     'Input quote character (aliased as --in-quote-char.') do |value|
+  options[:input_quote_char] = value
+end
+parser.on('--input-row-sep=SEPARATOR',
+     'Input row separator string (aliased as --in-row-sep).'
+) do |value|
+  options[:input_row_sep] = value
+end
+parser.on('--output-col-sep=SEPARATOR',
+     'Output column separator string (aliased as --out-col-sep).'
+) do |value|
+  options[:output_col_sep] = value
+end
+parser.on('--output-quote-char=CHAR',
+     'Output quote character (aliased as --out-quote-char).') do |value|
+  options[:output_quote_char] = value
+end
+parser.on('--output-row-sep=SEPARATOR',
+     'Output row separator string (aliased as --out-row-sep).'
+) do |value|
+  options[:output_row_sep] = value
+end
+
+parser.separator(nil)
+parser.separator('Input/Output Options')
+
+parser.separator(nil)
+parser.on('-c', '--col-sep=SEPARATOR',
+     'Column separator string.') do |value|
+  options[:col_sep] = value
+end
+parser.on('-q', '--quote-char=CHAR',
+     'Quote character.') do |value|
+  options[:quote_char] = value
+end
+parser.on('-r', '--row-sep=SEPARATOR',
+     'Row separator string.'
+) do |value|
+  options[:row_sep] = value
+end
+
+parser.separator(nil)
+parser.separator('Generic Options')
+parser.separator(nil)
+
+parser.on('-h', '--help', 'Prints this help.') do
+  puts parser
+  exit
+end
+
+parser.on('-v', '--version', 'Prints version.') do
+  puts CSV::VERSION
+  exit
+end
+
+parser.parse!
+
+CSV.filter(**options) do |row|
+end
diff --git a/test/csv/filter/test_filter.rb b/test/csv/filter/test_filter.rb
new file mode 100644
index 00000000..10aceb82
--- /dev/null
+++ b/test/csv/filter/test_filter.rb
@@ -0,0 +1,749 @@
+# -*- coding: utf-8 -*-
+# frozen_string_literal: false
+
+require_relative '../helper'
+
+require 'shellwords'
+require 'csv'
+
+class TestFilter < Test::Unit::TestCase
+
+  # Names and aliases for options.
+  CliOptionNames = {
+    # Input options.
+    converters: %w[--converters],
+    empty_value: %w[--empty_value],
+    field_size_limit: %w[--field_size_limit],
+    headers: %w[--headers],
+    header_converters: %w[--header_converters],
+    input_col_sep: %w[--input_col_sep --in_col_sep],
+    input_quote_char: %w[--input_quote_char --in_quote_char],
+    input_row_sep: %w[--input_row_sep --in_row_sep],
+    liberal_parsing: %w[--liberal_parsing],
+    nil_value: %w[--nil_value],
+    return_headers: %w[--return_headers],
+    skip_blanks: %w[--skip_blanks],
+    skip_lines: %w[--skip_lines],
+    strip: %w[--strip],
+    unconverted_fields: %w[--unconverted_fields],
+    # Output options.
+    force_quotes: %w[--force_quotes],
+    output_col_sep: %w[--output_col_sep --out_col_sep],
+    output_quote_char: %w[--output_quote_char --out_quote_char],
+    output_row_sep: %w[--output_row_sep --out_row_sep],
+    quote_empty: %w[--quote_empty],
+    write_converters: %w[--write_converters],
+    write_headers: %w[--write_headers],
+    write_nil_value: %w[--write_nil_value],
+    write_empty_value: %w[--write_empty_value],
+    # Input/output options.
+    col_sep: %w[-c --col_sep],
+    row_sep: %w[-r --row_sep],
+    quote_char: %w[-q --quote_char],
+  }
+
+  class Option
+
+    attr_accessor :sym, :cli_option_names, :api_argument_value, :cli_argument_value
+
+    def initialize(sym = nil, api_argument_value = nil)
+      self.sym = sym || :nil
+      self.cli_option_names = CliOptionNames.fetch(self.sym)
+      self.api_argument_value = api_argument_value
+      if api_argument_value.kind_of?(Array)
+        cli_argument_a = []
+        api_argument_value.each do |ele|
+          cli_argument_a.push(ele.to_s)
+        end
+        self.cli_argument_value = cli_argument_a.join(',')
+      else
+        self.cli_argument_value = api_argument_value
+      end
+    end
+
+  end
+
+  RowSep = "\n"
+  ColSep = ','
+  QuoteChar = '"'
+  Rows = [
+    %w[aaa bbb ccc],
+    %w[ddd eee fff],
+  ]
+
+  # Two methods copied from module Minitest::Assertions.
+
+  def _synchronize # :nodoc:
+    yield
+  end
+
+  def capture_subprocess_io
+    _synchronize do
+      begin
+        require "tempfile"
+
+        captured_stdout, captured_stderr = Tempfile.new("out"), Tempfile.new("err")
+
+        orig_stdout, orig_stderr = $stdout.dup, $stderr.dup
+        $stdout.reopen captured_stdout
+        $stderr.reopen captured_stderr
+
+        yield
+
+        $stdout.rewind
+        $stderr.rewind
+
+        return captured_stdout.read, captured_stderr.read
+      ensure
+        $stdout.reopen orig_stdout
+        $stderr.reopen orig_stderr
+
+        orig_stdout.close
+        orig_stderr.close
+        captured_stdout.close!
+        captured_stderr.close!
+      end
+    end
+  end
+
+  def setup
+    $TEST_DEBUG = false
+  end
+
+  def debug(label, value, newline: false)
+    return unless $TEST_DEBUG
+    print("\n") if newline
+    printf("%15s: %s\n", label, value.inspect)
+  end
+
+  def get_test_name
+    caller.each do |x|
+      method_name = x.split(' ').last.gsub(/\W/, '')
+      return method_name if method_name.start_with?('test')
+    end
+    raise RuntimeError.new('No test method name found.')
+  end
+
+  def do_test(debugging: false)
+    unless debugging
+      yield
+      return
+    end
+    get_test_name
+    $TEST_DEBUG = true
+    test_name = get_test_name
+    debug('BEGIN', test_name, newline: true)
+    yield
+    debug('END', test_name)
+    $TEST_DEBUG = false
+  end
+
+  # Return CSV string generated from rows and options.
+  def make_csv_s(rows: Rows, **options)
+    csv_s = CSV.generate(**options) do|csv|
+      rows.each do |row|
+        csv << row
+      end
+    end
+    csv_s
+  end
+
+  # Return filepath of file containing CSV data.
+  def csv_filepath(csv_in_s, dirpath, option_sym)
+    filename = "#{option_sym}.csv"
+    filepath = File.join(dirpath, filename)
+    File.write(filepath, csv_in_s)
+    filepath
+  end
+
+  # Return stdout and stderr from CLI execution.
+  def execute_in_cli(filepath, cli_options_s = '')
+    debug('cli_options_s', cli_options_s)
+    command = "cat #{filepath} | ruby bin/csv-filter #{cli_options_s}"
+    capture_subprocess_io do
+      system(command)
+    end
+  end
+
+  # Return CLI results for options.
+  def cli_results_for_options(filepath, cli_option_name, primary_option, options)
+    cli_options = [{name: cli_option_name, value: primary_option.cli_argument_value}]
+    options.each do |option|
+      cli_options.push({name: option.cli_option_names.first, value: option.cli_argument_value})
+    end
+    cli_options_s = ''
+    cli_options.each do |cli_option|
+      cli_options_s += " #{cli_option[:name]}"
+      value = cli_option[:value]
+      cli_options_s += " #{Shellwords.escape(value)}" unless value == :no_argument
+    end
+    execute_in_cli(filepath, cli_options_s)
+  end
+
+  # Return API result for options.
+  def api_result(filepath, primary_option, options)
+    api_options = {primary_option.sym => primary_option.api_argument_value}
+    options.each do |option|
+      api_options[option.sym] = option.api_argument_value
+    end
+    api_options.transform_values! {|value| value == :no_argument ? true : value }
+    csv_in_s = File.read(filepath)
+    debug('api_options_h', api_options)
+    api_out_s = get_via_api(csv_in_s, **api_options)
+    return api_out_s
+  end
+
+  # Return results for CLI-only option (or invalid option).
+  def results_for_cli_option(option_name)
+    cli_out_s = ''
+    cli_err_s = ''
+    Dir.mktmpdir do |dirpath|
+      sym = option_name.to_sym
+      filepath = csv_filepath('', dirpath, sym)
+      cli_out_s, cli_err_s = execute_in_cli(filepath, option_name)
+    end
+    [cli_out_s, cli_err_s]
+  end
+
+  # Get and return the actual output from the API.
+  def get_via_api(csv_in_s, **api_options)
+    cli_out_s = ''
+    CSV.filter(csv_in_s, cli_out_s, **api_options) {|row| }
+    cli_out_s
+  end
+
+  # Verify that the CLI behaves the same as the API.
+  # Return the actual output.
+  def verify_cli(csv_in_s, options)
+    options = options.dup # Don't modify caller's options.
+    api_out_s = ''
+    cli_out_s = ''
+    cli_err_s = ''
+    saved_out_s = nil
+    Dir.mktmpdir do |dirpath|
+      primary_option = options.shift
+      filepath = csv_filepath(csv_in_s, dirpath, primary_option.sym)
+      primary_option.cli_option_names.each do |cli_option_name|
+        # Get expected output string (from API).
+        api_out_s = api_result(filepath, primary_option, options)
+        # Get actual output and error strings (from CLI).
+        cli_out_s, cli_err_s = cli_results_for_options(filepath, cli_option_name, primary_option, options)
+        debug('csv_in_s', csv_in_s)
+        debug('api_out_s', api_out_s)
+        debug('cli_out_s', cli_out_s)
+        debug('cli_err_s', cli_err_s)
+        assert_empty(cli_err_s)
+        assert_equal(api_out_s, cli_out_s)
+        # Output string should be the same for all iterations.
+        saved_out_s = cli_out_s if saved_out_s.nil?
+        assert_equal(saved_out_s, cli_out_s)
+      end
+    end
+    cli_out_s
+  end
+
+  # Invalid option.
+
+  def test_invalid_option
+    do_test(debugging: false) do
+      %w[-Z --ZZZ].each do |option_name|
+        cli_out_s, cli_err_s = results_for_cli_option(option_name)
+        assert_empty(cli_out_s)
+        assert_match(/OptionParser::InvalidOption/, cli_err_s)
+      end
+    end
+  end
+
+  # No options.
+
+  def test_no_options
+    do_test(debugging: false) do
+      csv_in_s = make_csv_s
+      cli_out_s = get_via_api(csv_in_s)
+      assert_equal(csv_in_s, cli_out_s)
+    end
+  end
+
+  # General options
+
+  def test_option_h
+    do_test(debugging: false) do
+      %w[-h --help].each do |option_name|
+        cli_out_s, cli_err_s = results_for_cli_option(option_name)
+        assert_match(/Usage/, cli_out_s)
+        assert_empty(cli_err_s)
+      end
+    end
+  end
+
+  def test_option_v
+    do_test(debugging: false) do
+      %w[-v --version].each do |option_name|
+        cli_out_s, cli_err_s = results_for_cli_option(option_name)
+        assert_match(/\d+\.\d+\.\d+/, cli_out_s)
+        assert_empty(cli_err_s)
+      end
+    end
+  end
+
+  # Input options.
+
+  def test_option_converters
+    do_test(debugging: false) do
+      converters = %i[integer float]
+      rows = [
+        ['foo', 0],
+        ['bar', 1.1],
+      ]
+      csv_in_s = make_csv_s(rows: rows)
+      options = [
+        Option.new(:converters, converters)
+      ]
+      cli_out_s = verify_cli(csv_in_s, options)
+      assert_equal(csv_in_s, cli_out_s)
+    end
+  end
+
+  # def test_option_empty_value
+  #   do_test(debugging: false) do
+  #     empty_value = 0
+  #     csv_in_s = 'a,"",b,"",c'
+  #     options = [
+  #       Option.new(:empty_value, empty_value)
+  #     ]
+  #     cli_out_s = verify_cli(csv_in_s, options)
+  #     refute_equal(csv_in_s, cli_out_s)
+  #   end
+  # end
+
+  def test_option_field_size_limit
+    do_test(debugging: false) do
+      field_size_limit = 2
+      csv_in_s = make_csv_s
+      options = [
+        Option.new(:field_size_limit, field_size_limit)
+      ]
+      begin
+        verify_cli(csv_in_s, options)
+      rescue CSV::MalformedCSVError => x
+        assert_match('Field size exceeded', x.message)
+      end
+    end
+  end
+
+  def test_option_headers
+    do_test(debugging: false) do
+      headers = true
+      csv_in_s = make_csv_s
+      options = [
+        Option.new(:headers, headers)
+      ]
+      verify_cli(csv_in_s, options)
+    end
+  end
+
+  def test_option_header_converters
+    do_test(debugging: false) do
+      header_converters = %i[downcase symbol]
+      rows = [
+        ['Foo', 'Bar'],
+        ['0', 1],
+      ]
+      csv_in_s = make_csv_s(rows: rows)
+      options = [
+        Option.new(:headers, true),
+        Option.new(:header_converters, header_converters)
+      ]
+      verify_cli(csv_in_s, options)
+    end
+  end
+
+  def test_option_liberal_parsing
+    do_test(debugging: false) do
+      liberal_parsing = :no_argument
+      csv_in_s = 'is,this "three, or four",fields'
+      options = [
+        Option.new(:liberal_parsing, liberal_parsing)
+      ]
+      cli_out_s = verify_cli(csv_in_s, options)
+      refute_equal(csv_in_s, cli_out_s)
+    end
+  end
+
+  # def test_option_nil_value
+  #   do_test(debugging: false) do
+  #     nil_value = 0
+  #     csv_in_s = 'a,,b,,c'
+  #     options = [
+  #       Option.new(:nil_value, nil_value)
+  #     ]
+  #     cli_out_s = verify_cli(csv_in_s, options)
+  #     refute_equal(csv_in_s, cli_out_s)
+  #   end
+  # end
+
+  # def test_option_return_headers
+  #   do_test(debugging: false) do
+  #     return_headers = :no_argument
+  #     csv_in_s = make_csv_s
+  #     options = [
+  #       Option.new(:return_headers, return_headers)
+  #     ]
+  #     cli_out_s = verify_cli(csv_in_s, options)
+  #     assert_equal(csv_in_s, cli_out_s)
+  #   end
+  # end
+
+  # def test_option_skip_blanks
+  #   do_test(debugging: false) do
+  #     skip_blanks = :no_argument
+  #     rows = Rows.dup
+  #     rows.insert(1, [])
+  #     csv_in_s = make_csv_s(rows: rows)
+  #     options = [
+  #       Option.new(:skip_blanks, skip_blanks)
+  #     ]
+  #     cli_out_s = verify_cli(csv_in_s, options)
+  #     refute_equal(csv_in_s, cli_out_s)
+  #   end
+  # end
+
+  # def test_option_skip_lines
+  #   do_test(debugging: false) do
+  #     skip_lines = '#'
+  #     rows = Rows.dup
+  #     rows.insert(1, ['# Boo!'])
+  #     csv_in_s = make_csv_s(rows: rows)
+  #     options = [
+  #       Option.new(:skip_lines, skip_lines)
+  #     ]
+  #     cli_out_s = verify_cli(csv_in_s, options)
+  #     refute_equal(csv_in_s, cli_out_s)
+  #   end
+  # end
+
+  # def test_option_strip
+  #   do_test(debugging: false) do
+  #     strip = :no_argument
+  #     rows = Rows.map do |row|
+  #       row.map do |col|
+  #         " #{col} "
+  #       end
+  #     end
+  #     csv_in_s = make_csv_s(rows: rows)
+  #     options = [
+  #       Option.new(:strip, strip)
+  #     ]
+  #     cli_out_s = verify_cli(csv_in_s, options)
+  #     refute_equal(csv_in_s, cli_out_s)
+  #   end
+  # end
+
+  # def test_option_unconverted_fields
+  #   do_test(debugging: false) do
+  #     unconverted_fields = :no_argument
+  #     csv_in_s = make_csv_s
+  #     options = [
+  #       Option.new(:unconverted_fields, unconverted_fields)
+  #     ]
+  #     cli_out_s = verify_cli(csv_in_s, options)
+  #     assert_equal(csv_in_s, cli_out_s)
+  #   end
+  # end
+
+  # Output options.
+
+  # def test_option_force_quotes
+  #   do_test(debugging: false) do
+  #     force_quotes = :no_argument
+  #     csv_in_s = make_csv_s
+  #     options = [
+  #       Option.new(:force_quotes, force_quotes),
+  #     ]
+  #     cli_out_s = verify_cli(csv_in_s, options)
+  #     refute_equal(csv_in_s, cli_out_s)
+  #   end
+  # end
+
+  # def test_option_quote_empty
+  #   do_test(debugging: false) do
+  #     quote_empty = true
+  #     csv_in_s = "\"\"\"\",\"\"\n"
+  #     options = [
+  #       Option.new(:quote_empty, quote_empty),
+  #     ]
+  #     cli_out_s = verify_cli(csv_in_s, options)
+  #     assert_equal(csv_in_s, cli_out_s)
+  #   end
+  # end
+
+  # def test_option_write_converters
+  #   do_test(debugging: false) do
+  #     cli_out_s, cli_err_s = results_for_cli_option('--write_converters')
+  #     assert_empty(cli_out_s)
+  #     assert_match(/NotImplementedError/, cli_err_s)
+  #   end
+  # end
+
+  # def test_option_write_headers
+  #   do_test(debugging: false) do
+  #     write_headers = :no_argument
+  #     csv_in_s = make_csv_s
+  #     options = [
+  #       Option.new(:write_headers, write_headers),
+  #       Option.new(:headers, true),
+  #     ]
+  #     cli_out_s = verify_cli(csv_in_s, options)
+  #     assert_equal(csv_in_s, cli_out_s)
+  #   end
+  # end
+
+  # def test_option_write_empty_value
+  #   do_test(debugging: false) do
+  #     write_empty_value = 'x'
+  #     csv_in_s = "a,\"\",c,\"\"\n"
+  #     options = [
+  #       Option.new(:write_empty_value, write_empty_value),
+  #     ]
+  #     cli_out_s = verify_cli(csv_in_s, options)
+  #     refute_equal(csv_in_s, cli_out_s)
+  #   end
+  # end
+
+  # def test_option_write_nil_value
+  #   do_test(debugging: false) do
+  #     write_nil_value = 'x'
+  #     csv_in_s = "a,,c,\n"
+  #     options = [
+  #       Option.new(:write_nil_value, write_nil_value),
+  #     ]
+  #     cli_out_s = verify_cli(csv_in_s, options)
+  #     refute_equal(csv_in_s, cli_out_s)
+  #   end
+  # end
+
+  # Input/output options.
+
+  def test_option_c
+    do_test(debugging: false) do
+      col_sep = 'X'
+      csv_in_s = make_csv_s(col_sep: col_sep)
+      options = [
+        Option.new(:col_sep, col_sep)
+      ]
+      cli_out_s = verify_cli(csv_in_s, options)
+      assert_equal(csv_in_s, cli_out_s)
+    end
+  end
+
+  def test_option_input_col_sep
+    do_test(debugging: false) do
+      input_col_sep = 'X'
+      csv_in_s = make_csv_s(col_sep: input_col_sep)
+      options = [
+        Option.new(:input_col_sep, input_col_sep)
+      ]
+      cli_out_s = verify_cli(csv_in_s, options)
+      refute_equal(csv_in_s, cli_out_s)
+    end
+  end
+
+  def test_option_output_col_sep
+    do_test(debugging: false) do
+      output_col_sep = 'X'
+      csv_in_s = make_csv_s
+      options = [
+        Option.new(:output_col_sep, output_col_sep)
+      ]
+      cli_out_s = verify_cli(csv_in_s, options)
+      refute_equal(csv_in_s, cli_out_s)
+    end
+  end
+
+  def test_options_c_and_input_col_sep
+    do_test(debugging: false) do
+      input_col_sep = 'X'
+      col_sep = 'Y'
+      csv_in_s = make_csv_s(col_sep: input_col_sep)
+      options = [
+        Option.new(:col_sep, col_sep),
+        Option.new(:input_col_sep, input_col_sep),
+      ]
+      cli_out_s = verify_cli(csv_in_s, options)
+      refute_equal(csv_in_s, cli_out_s)
+      cli_out_s = verify_cli(csv_in_s, options.reverse)
+      assert_equal(csv_in_s, cli_out_s)
+    end
+  end
+
+  def test_options_c_and_output_col_sep
+    do_test(debugging: false) do
+      col_sep = 'X'
+      output_col_sep = 'Y'
+      csv_in_s = make_csv_s(col_sep: col_sep)
+      options = [
+        Option.new(:col_sep, col_sep),
+        Option.new(:output_col_sep, output_col_sep),
+      ]
+      cli_out_s = verify_cli(csv_in_s, options)
+      refute_equal(csv_in_s, cli_out_s)
+      cli_out_s = verify_cli(csv_in_s, options.reverse)
+      assert_equal(csv_in_s, cli_out_s)
+    end
+  end
+
+  def test_options_input_col_sep_and_output_col_sep
+    do_test(debugging: false) do
+      input_col_sep = 'X'
+      output_col_sep = 'Y'
+      csv_in_s = make_csv_s(col_sep: input_col_sep)
+      options = [
+        Option.new(:input_col_sep, input_col_sep),
+        Option.new(:output_col_sep, output_col_sep),
+      ]
+      cli_out_s = verify_cli(csv_in_s, options)
+      refute_equal(csv_in_s, cli_out_s)
+      cli_out_s = verify_cli(csv_in_s, options.reverse)
+      refute_equal(csv_in_s, cli_out_s)
+    end
+  end
+
+  def test_option_r
+    do_test(debugging: false) do
+      row_sep = 'X'
+      csv_in_s = make_csv_s(row_sep: row_sep)
+      options = [
+        Option.new(:row_sep, row_sep)
+      ]
+      cli_out_s = verify_cli(csv_in_s, options)
+      assert_equal(csv_in_s, cli_out_s)
+    end
+  end
+
+  def test_option_input_row_sep
+    do_test(debugging: false) do
+      input_row_sep = 'A'
+      csv_in_s = make_csv_s(row_sep: input_row_sep)
+      options = [
+        Option.new(:input_row_sep, input_row_sep)
+      ]
+      cli_out_s = verify_cli(csv_in_s, options)
+      refute_equal(csv_in_s, cli_out_s)
+    end
+  end
+
+  def test_option_output_row_sep
+    do_test(debugging: false) do
+      output_row_sep = 'A'
+      csv_in_s = make_csv_s(row_sep: output_row_sep)
+      options = [
+        Option.new(:input_row_sep, output_row_sep)
+      ]
+      cli_out_s = verify_cli(csv_in_s, options)
+      refute_equal(csv_in_s, cli_out_s)
+    end
+  end
+
+  def test_options_r_and_input_row_sep
+    do_test(debugging: false) do
+      input_row_sep = 'X'
+      row_sep = 'Y'
+      csv_in_s = make_csv_s(row_sep: input_row_sep)
+      options = [
+        Option.new(:row_sep, row_sep),
+        Option.new(:input_row_sep, input_row_sep),
+      ]
+      cli_out_s = verify_cli(csv_in_s, options)
+      refute_equal(csv_in_s, cli_out_s)
+      cli_out_s = verify_cli(csv_in_s, options.reverse)
+      # Used match instead of equal here b/c there seems to be an extra 'Y'
+      # at the end of the cli_out_s (possibly a CSV bug?).
+      assert_match(csv_in_s, cli_out_s)
+    end
+  end
+
+  def test_options_r_and_output_row_sep
+    do_test(debugging: false) do
+      row_sep = 'X'
+      output_row_sep = 'Y'
+      csv_in_s = make_csv_s(row_sep: row_sep)
+      options = [
+        Option.new(:row_sep, row_sep),
+        Option.new(:output_row_sep, output_row_sep),
+      ]
+      cli_out_s = verify_cli(csv_in_s, options)
+      refute_equal(csv_in_s, cli_out_s)
+      cli_out_s = verify_cli(csv_in_s, options.reverse)
+      assert_equal(csv_in_s, cli_out_s)
+    end
+  end
+
+  def test_options_input_row_sep_and_output_row_sep
+    do_test(debugging: false) do
+      input_row_sep = 'X'
+      output_row_sep = 'Y'
+      csv_in_s = make_csv_s(row_sep: input_row_sep)
+      options = [
+        Option.new(:input_row_sep, input_row_sep),
+        Option.new(:output_row_sep, output_row_sep),
+      ]
+      cli_out_s = verify_cli(csv_in_s, options)
+      refute_equal(csv_in_s, cli_out_s)
+      cli_out_s = verify_cli(csv_in_s, options.reverse)
+      refute_equal(csv_in_s, cli_out_s)
+    end
+  end
+
+  def test_option_q
+    do_test(debugging: false) do
+      quote_char = "'"
+      rows = [
+        ['foo', 0],
+        ["'bar'", 1],
+        ['"baz"', 2],
+      ]
+      csv_in_s = make_csv_s(rows: rows, quote_char: quote_char)
+      options = [
+        Option.new(:quote_char, quote_char)
+      ]
+      cli_out_s = verify_cli(csv_in_s, options)
+      assert_equal(csv_in_s, cli_out_s)
+    end
+  end
+
+  def test_option_input_quote_char
+    do_test(debugging: false) do
+      input_quote_char = "'"
+      rows = [
+        ['foo', 0],
+        ["'bar'", 1],
+        ['"baz"', 2],
+      ]
+      csv_in_s = make_csv_s(rows: rows, quote_char: input_quote_char)
+      options = [
+        Option.new(:input_quote_char, input_quote_char)
+      ]
+      cli_out_s = verify_cli(csv_in_s, options)
+      refute_equal(csv_in_s, cli_out_s)
+    end
+  end
+
+  # def test_option_output_quote_char
+  #   do_test(debugging: false) do
+  #     output_quote_char = "X"
+  #     rows = [
+  #       ['foo', 0],
+  #       ["'bar'", 1],
+  #       ['"baz"', 2],
+  #     ]
+  #     csv_in_s = make_csv_s(rows: rows)
+  #     options = [
+  #       Option.new(:output_quote_char, output_quote_char),
+  #       Option.new(:force_quotes, :no_argument)
+  #     ]
+  #     cli_out_s = verify_cli(csv_in_s, options)
+  #     refute_equal(csv_in_s, cli_out_s)
+  #   end
+  # end
+
+end