diff --git a/.github/workflows/ruby.yml b/.github/workflows/ruby.yml
index fd70f479..115ea992 100644
--- a/.github/workflows/ruby.yml
+++ b/.github/workflows/ruby.yml
@@ -26,6 +26,7 @@ jobs:
           - "3.0"
           - 3.1
           - 3.2
+          - 3.3
           - head
           - truffleruby
           - truffleruby-head
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 79ad3fc6..85981362 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,24 @@
 
 # SmarterCSV 1.x Change Log
 
+## 1.10.0 (2023-12-31) ⚡ BREAKING ⚡
+
+  * BREAKING CHANGES:
+    
+    Changed behavior:
+     + when `user_provided_headers` are provided:
+       * if they are not unique, an exception will now be raised
+       * they are taken "as is", no header transformations can be applied
+       * when they are given as strings or as symbols, it is assumed that this is the desired format
+       * the value of the `strings_as_keys` options will be ignored
+         
+     + option `duplicate_header_suffix` now defaults to `''` instead of `nil`.
+       * this allows automatic disambiguation when processing of CSV files with duplicate headers, by appending a number
+       * explicitly set this option to `nil` to get the behavior from previous versions.
+
+  * performance and memory improvements
+  * code refactor
+
 ## 1.9.3 (2023-12-16)
   * raise SmarterCSV::IncorrectOption when `user_provided_headers` are empty
   * code refactor / no functional changes
diff --git a/README.md b/README.md
index 5018ab4e..dfdf9b4f 100644
--- a/README.md
+++ b/README.md
@@ -2,15 +2,33 @@
 # SmarterCSV
 
  [![codecov](https://codecov.io/gh/tilo/smarter_csv/branch/main/graph/badge.svg?token=1L7OD80182)](https://codecov.io/gh/tilo/smarter_csv) [![Gem Version](https://badge.fury.io/rb/smarter_csv.svg)](http://badge.fury.io/rb/smarter_csv)
- 
+
+
+#### LATEST CHANGES
+
+* Version 1.10.0 has BREAKING CHANGES:
+
+    Changed behavior:
+     + when `user_provided_headers` are provided:
+       * if they are not unique, an exception will now be raised
+       * they are taken "as is", no header transformations can be applied
+       * when they are given as strings or as symbols, it is assumed that this is the desired format
+       * the value of the `strings_as_keys` options will be ignored
+         
+     + option `duplicate_header_suffix` now defaults to `''` instead of `nil`.
+       * this allows automatic disambiguation when processing of CSV files with duplicate headers, by appending a number
+       * explicitly set this option to `nil` to get the behavior from previous versions.
+
 #### Development Branches
 
 * default branch is `main` for 1.x development
-* 2.x development is on `2.0-development` (check this branch for 2.0 documentation)
+  
+* 2.x development is on `2.0-development` (check this branch for 2.0 documentation) 
+  - This is an EXPERIMENTAL branch - DO NOT USE in production
 
-#### Work towards Future Version 2.0
+#### Work towards Future Version 2.x
 
-* Work towards SmarterCSV 2.0 is still ongoing, with improved features, and more streamlined options, but consider it as experimental at this time.
+* Work towards SmarterCSV 2.x is still ongoing, with improved features, and more streamlined options, but consider it as experimental at this time.
   Please check the [2.0-develop branch](https://github.com/tilo/smarter_csv/tree/2.0-develop), open any issues and pull requests with mention of tag v2.0.
 
 ---------------
@@ -83,10 +101,11 @@ $ hexdump -C spec/fixtures/bom_test_feff.csv
 00000030  0a 33 38 37 35 39 31 35  30 2c 71 75 69 7a 7a 65  |.38759150,quizze|
 00000040  73 2c 35 36 37 38 0d 0a                           |s,5678..|
 ```
+
 ### Articles
 * [Processing 1.4 Million CSV Records in Ruby, fast ](https://lcx.wien/blog/processing-14-million-csv-records-in-ruby/)
 * [Speeding up CSV parsing with parallel processing](http://xjlin0.github.io/tech/2015/05/25/faster-parsing-csv-with-parallel-processing)
-  
+
 ### Examples
 
 Here are some examples to demonstrate the versatility of SmarterCSV.
@@ -281,7 +300,8 @@ The options and the block are optional.
      | :headers_in_file            |   true   | Whether or not the file contains headers as the first line.                          |
      |                             |          | Important if the file does not contain headers,                                      |
      |                             |          | otherwise you would lose the first line of data.                                     |
-     | :duplicate_header_suffix    |   nil    | If set, adds numbers to duplicated headers and separates them by the given suffix    |
+     | :duplicate_header_suffix    |   ''     | Adds numbers to duplicated headers and separates them by the given suffix.           |
+     |                             |          | Set this to nil to raise `DuplicateHeaders` error instead (previous behavior)        |
      | :user_provided_headers      |   nil    | *careful with that axe!*                                                             |
      |                             |          | user provided Array of header strings or symbols, to define                          |
      |                             |          | what headers should be used, overriding any in-file headers.                         |
diff --git a/lib/smarter_csv.rb b/lib/smarter_csv.rb
index d4d94a2c..26b8914d 100644
--- a/lib/smarter_csv.rb
+++ b/lib/smarter_csv.rb
@@ -5,13 +5,21 @@
 require "smarter_csv/options_processing"
 require "smarter_csv/auto_detection"
 require "smarter_csv/variables"
+require 'smarter_csv/header_transformations'
+require 'smarter_csv/header_validations'
 require "smarter_csv/headers"
+require "smarter_csv/hash_transformations"
 require "smarter_csv/parse"
 
+# load the C-extension:
 case RUBY_ENGINE
 when 'ruby'
   begin
     if `uname -s`.chomp == 'Darwin'
+      #
+      # Please report if you see cases where the rake-compiler is building x86_64 code on arm64 cpus:
+      # https://github.com/rake-compiler/rake-compiler/issues/231
+      #
       require 'smarter_csv/smarter_csv.bundle'
     else
       # :nocov:
diff --git a/lib/smarter_csv/hash_transformations.rb b/lib/smarter_csv/hash_transformations.rb
new file mode 100644
index 00000000..f6b4d538
--- /dev/null
+++ b/lib/smarter_csv/hash_transformations.rb
@@ -0,0 +1,91 @@
+# frozen_string_literal: true
+
+module SmarterCSV
+  class << self
+    def hash_transformations(hash, options)
+      # there may be unmapped keys, or keys purposedly mapped to nil or an empty key..
+      # make sure we delete any key/value pairs from the hash, which the user wanted to delete:
+      remove_empty_values = options[:remove_empty_values] == true
+      remove_zero_values = options[:remove_zero_values]
+      remove_values_matching = options[:remove_values_matching]
+      convert_to_numeric = options[:convert_values_to_numeric]
+      value_converters = options[:value_converters]
+
+      hash.each_with_object({}) do |(k, v), new_hash|
+        next if k.nil? || k == '' || k == :""
+        next if remove_empty_values && (has_rails ? v.blank? : blank?(v))
+        next if remove_zero_values && v.is_a?(String) && v =~ /^(0+|0+\.0+)$/ # values are Strings
+        next if remove_values_matching && v =~ remove_values_matching
+
+        # deal with the :only / :except options to :convert_values_to_numeric
+        if convert_to_numeric && !limit_execution_for_only_or_except(options, :convert_values_to_numeric, k)
+          if v =~ /^[+-]?\d+\.\d+$/
+            v = v.to_f
+          elsif v =~ /^[+-]?\d+$/
+            v = v.to_i
+          end
+        end
+
+        converter = value_converters[k] if value_converters
+        v = converter.convert(v) if converter
+
+        new_hash[k] = v
+      end
+    end
+
+    # def hash_transformations(hash, options)
+    #   # there may be unmapped keys, or keys purposedly mapped to nil or an empty key..
+    #   # make sure we delete any key/value pairs from the hash, which the user wanted to delete:
+    #   hash.delete(nil)
+    #   hash.delete('')
+    #   hash.delete(:"")
+
+    #   if options[:remove_empty_values] == true
+    #     hash.delete_if{|_k, v| has_rails ? v.blank? : blank?(v)}
+    #   end
+
+    #   hash.delete_if{|_k, v| !v.nil? && v =~ /^(0+|0+\.0+)$/} if options[:remove_zero_values] # values are Strings
+    #   hash.delete_if{|_k, v| v =~ options[:remove_values_matching]} if options[:remove_values_matching]
+
+    #   if options[:convert_values_to_numeric]
+    #     hash.each do |k, v|
+    #       # deal with the :only / :except options to :convert_values_to_numeric
+    #       next if limit_execution_for_only_or_except(options, :convert_values_to_numeric, k)
+
+    #       # convert if it's a numeric value:
+    #       case v
+    #       when /^[+-]?\d+\.\d+$/
+    #         hash[k] = v.to_f
+    #       when /^[+-]?\d+$/
+    #         hash[k] = v.to_i
+    #       end
+    #     end
+    #   end
+
+    #   if options[:value_converters]
+    #     hash.each do |k, v|
+    #       converter = options[:value_converters][k]
+    #       next unless converter
+
+    #       hash[k] = converter.convert(v)
+    #     end
+    #   end
+
+    #   hash
+    # end
+
+    protected
+
+    # acts as a road-block to limit processing when iterating over all k/v pairs of a CSV-hash:
+    def limit_execution_for_only_or_except(options, option_name, key)
+      if options[option_name].is_a?(Hash)
+        if options[option_name].has_key?(:except)
+          return true if Array(options[option_name][:except]).include?(key)
+        elsif options[option_name].has_key?(:only)
+          return true unless Array(options[option_name][:only]).include?(key)
+        end
+      end
+      false
+    end
+  end
+end
diff --git a/lib/smarter_csv/header_transformations.rb b/lib/smarter_csv/header_transformations.rb
new file mode 100644
index 00000000..fac326e1
--- /dev/null
+++ b/lib/smarter_csv/header_transformations.rb
@@ -0,0 +1,63 @@
+# frozen_string_literal: true
+
+module SmarterCSV
+  class << self
+    # transform the headers that were in the file:
+    def header_transformations(header_array, options)
+      header_array.map!{|x| x.gsub(%r/#{options[:quote_char]}/, '')}
+      header_array.map!{|x| x.strip} if options[:strip_whitespace]
+
+      unless options[:keep_original_headers]
+        header_array.map!{|x| x.gsub(/\s+|-+/, '_')}
+        header_array.map!{|x| x.downcase} if options[:downcase_header]
+      end
+
+      # detect duplicate headers and disambiguate
+      header_array = disambiguate_headers(header_array, options) if options[:duplicate_header_suffix]
+      # symbolize headers
+      header_array = header_array.map{|x| x.to_sym } unless options[:strings_as_keys] || options[:keep_original_headers]
+      # doesn't make sense to re-map when we have user_provided_headers
+      header_array = remap_headers(header_array, options) if options[:key_mapping]
+
+      header_array
+    end
+
+    def disambiguate_headers(headers, options)
+      counts = Hash.new(0)
+      headers.map do |header|
+        counts[header] += 1
+        counts[header] > 1 ? "#{header}#{options[:duplicate_header_suffix]}#{counts[header]}" : header
+      end
+    end
+
+    # do some key mapping on the keys in the file header
+    # if you want to completely delete a key, then map it to nil or to ''
+    def remap_headers(headers, options)
+      key_mapping = options[:key_mapping]
+      if key_mapping.empty? || !key_mapping.is_a?(Hash) || key_mapping.keys.empty?
+        raise(SmarterCSV::IncorrectOption, "ERROR: incorrect format for key_mapping! Expecting hash with from -> to mappings")
+      end
+
+      key_mapping = options[:key_mapping]
+      # if silence_missing_keys are not set, raise error if missing header
+      missing_keys = key_mapping.keys - headers
+      # if the user passes a list of speciffic mapped keys that are optional
+      missing_keys -= options[:silence_missing_keys] if options[:silence_missing_keys].is_a?(Array)
+
+      unless missing_keys.empty? || options[:silence_missing_keys] == true
+        raise SmarterCSV::KeyMappingError, "ERROR: can not map headers: #{missing_keys.join(', ')}"
+      end
+
+      headers.map! do |header|
+        if key_mapping.has_key?(header)
+          key_mapping[header].nil? ? nil : key_mapping[header]
+        elsif options[:remove_unmapped_keys]
+          nil
+        else
+          header
+        end
+      end
+      headers
+    end
+  end
+end
diff --git a/lib/smarter_csv/header_validations.rb b/lib/smarter_csv/header_validations.rb
new file mode 100644
index 00000000..bd906da4
--- /dev/null
+++ b/lib/smarter_csv/header_validations.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module SmarterCSV
+  class << self
+    def header_validations(headers, options)
+      check_duplicate_headers(headers, options)
+      check_required_headers(headers, options)
+    end
+
+    def check_duplicate_headers(headers, _options)
+      header_counts = Hash.new(0)
+      headers.each { |header| header_counts[header] += 1 unless header.nil? }
+
+      duplicates = header_counts.select { |_, count| count > 1 }
+
+      unless duplicates.empty?
+        raise(SmarterCSV::DuplicateHeaders, "Duplicate Headers in CSV: #{duplicates.inspect}")
+      end
+    end
+
+    require 'set'
+
+    def check_required_headers(headers, options)
+      if options[:required_keys] && options[:required_keys].is_a?(Array)
+        headers_set = headers.to_set
+        missing_keys = options[:required_keys].select { |k| !headers_set.include?(k) }
+
+        unless missing_keys.empty?
+          raise SmarterCSV::MissingKeys, "ERROR: missing attributes: #{missing_keys.join(',')}"
+        end
+      end
+    end
+  end
+end
diff --git a/lib/smarter_csv/headers.rb b/lib/smarter_csv/headers.rb
index 98795f6e..cc557c69 100644
--- a/lib/smarter_csv/headers.rb
+++ b/lib/smarter_csv/headers.rb
@@ -17,11 +17,8 @@ def process_headers(filehandle, options)
 
         file_header_array, file_header_size = parse(header_line, options)
 
-        # header transformations:
-        file_header_array = transform_headers(file_header_array, options)
+        file_header_array = header_transformations(file_header_array, options)
 
-        # currently this is, but should not be called on user_provided headers
-        file_header_array = legacy_header_transformations(file_header_array, options)
       else
         unless options[:user_provided_headers]
           raise SmarterCSV::IncorrectOption, "ERROR: If :headers_in_file is set to false, you have to provide :user_provided_headers"
@@ -45,18 +42,10 @@ def process_headers(filehandle, options)
         end
 
         header_array = user_header_array
-
-        # these 3 steps should only be part of the header transformation when headers_in_file:
-        # -> breaking change when we move this to transform_headers()
-        #    see details in legacy_header_transformations()
-        #
-        header_array = legacy_header_transformations(header_array, options)
       else
         header_array = file_header_array
       end
 
-      validate_headers(header_array, options)
-
       [header_array, header_array.size]
     end
 
@@ -70,95 +59,6 @@ def preprocess_header_line(header_line, options)
       header_line
     end
 
-    # transform the headers that were in the file:
-    def transform_headers(header_array, options)
-      header_array.map!{|x| x.gsub(%r/#{options[:quote_char]}/, '')}
-      header_array.map!{|x| x.strip} if options[:strip_whitespace]
-
-      unless options[:keep_original_headers]
-        header_array.map!{|x| x.gsub(/\s+|-+/, '_')}
-        header_array.map!{|x| x.downcase} if options[:downcase_header]
-      end
-
-      header_array
-    end
-
-    def legacy_header_transformations(header_array, options)
-      # detect duplicate headers and disambiguate
-      #   -> user_provided_headers should not have duplicates!
-      header_array = disambiguate_headers(header_array, options) if options[:duplicate_header_suffix]
-      # symbolize headers
-      #   -> user_provided_headers should already be symbols or strings as needed
-      header_array = header_array.map{|x| x.to_sym } unless options[:strings_as_keys] || options[:keep_original_headers]
-      # doesn't make sense to re-map when we have user_provided_headers
-      header_array = remap_headers(header_array, options) if options[:key_mapping] && !options[:user_provided_headers]
-      header_array
-    end
-
-    def disambiguate_headers(headers, options)
-      counts = Hash.new(0)
-      headers.map do |header|
-        counts[header] += 1
-        counts[header] > 1 ? "#{header}#{options[:duplicate_header_suffix]}#{counts[header]}" : header
-      end
-    end
-
-    # do some key mapping on the keys in the file header
-    # if you want to completely delete a key, then map it to nil or to ''
-    def remap_headers(headers, options)
-      key_mapping = options[:key_mapping]
-      if key_mapping.empty? || !key_mapping.is_a?(Hash) || key_mapping.keys.empty?
-        raise(SmarterCSV::IncorrectOption, "ERROR: incorrect format for key_mapping! Expecting hash with from -> to mappings")
-      end
-
-      key_mapping = options[:key_mapping]
-      # if silence_missing_keys are not set, raise error if missing header
-      missing_keys = key_mapping.keys - headers
-      # if the user passes a list of speciffic mapped keys that are optional
-      missing_keys -= options[:silence_missing_keys] if options[:silence_missing_keys].is_a?(Array)
-
-      unless missing_keys.empty? || options[:silence_missing_keys] == true
-        raise SmarterCSV::KeyMappingError, "ERROR: can not map headers: #{missing_keys.join(', ')}"
-      end
-
-      headers.map! do |header|
-        if key_mapping.has_key?(header)
-          key_mapping[header].nil? ? nil : key_mapping[header]
-        elsif options[:remove_unmapped_keys]
-          nil
-        else
-          header
-        end
-      end
-      headers
-    end
-
-    # header_validations
-    def validate_headers(headers, options)
-      duplicate_headers = []
-      headers.compact.each do |k|
-        duplicate_headers << k if headers.select{|x| x == k}.size > 1
-      end
-
-      unless options[:user_provided_headers] || duplicate_headers.empty?
-        raise SmarterCSV::DuplicateHeaders, "ERROR: duplicate headers: #{duplicate_headers.join(',')}"
-      end
-
-      if options[:required_keys] && options[:required_keys].is_a?(Array)
-        missing_keys = []
-        options[:required_keys].each do |k|
-          missing_keys << k unless headers.include?(k)
-        end
-        raise SmarterCSV::MissingKeys, "ERROR: missing attributes: #{missing_keys.join(',')}" unless missing_keys.empty?
-      end
-    end
-
-    def enforce_utf8_encoding(header, options)
-      return header unless options[:force_utf8] || options[:file_encoding] !~ /utf-8/i
-
-      header.force_encoding('utf-8').encode('utf-8', invalid: :replace, undef: :replace, replace: options[:invalid_byte_sequence])
-    end
-
     def remove_comments_from_header(header, options)
       return header unless options[:comment_regexp]
 
diff --git a/lib/smarter_csv/options_processing.rb b/lib/smarter_csv/options_processing.rb
index 606c4963..6d14302f 100644
--- a/lib/smarter_csv/options_processing.rb
+++ b/lib/smarter_csv/options_processing.rb
@@ -9,7 +9,7 @@ module SmarterCSV
     comment_regexp: nil, # was: /\A#/,
     convert_values_to_numeric: true,
     downcase_header: true,
-    duplicate_header_suffix: nil,
+    duplicate_header_suffix: '', # was: nil,
     file_encoding: 'utf-8',
     force_simple_split: false,
     force_utf8: false,
diff --git a/lib/smarter_csv/smarter_csv.rb b/lib/smarter_csv/smarter_csv.rb
index d361704a..c0fcb459 100644
--- a/lib/smarter_csv/smarter_csv.rb
+++ b/lib/smarter_csv/smarter_csv.rb
@@ -16,12 +16,13 @@ def SmarterCSV.process(input, given_options = {}, &block) # rubocop:disable Lint
 
     options = process_options(given_options)
 
-    has_rails = !!defined?(Rails)
+    @enforce_utf8 = options[:force_utf8] || options[:file_encoding] !~ /utf-8/i
+    @verbose = options[:verbose]
 
     begin
       fh = input.respond_to?(:readline) ? input : File.open(input, "r:#{options[:file_encoding]}")
 
-      if (options[:force_utf8] || options[:file_encoding] =~ /utf-8/i) && (fh.respond_to?(:external_encoding) && fh.external_encoding != Encoding.find('UTF-8') || fh.respond_to?(:encoding) && fh.encoding != Encoding.find('UTF-8'))
+      if @enforce_utf8 && (fh.respond_to?(:external_encoding) && fh.external_encoding != Encoding.find('UTF-8') || fh.respond_to?(:encoding) && fh.encoding != Encoding.find('UTF-8'))
         puts 'WARNING: you are trying to process UTF-8 input, but did not open the input with "b:utf-8" option. See README file "NOTES about File Encodings".'
       end
 
@@ -35,6 +36,10 @@ def SmarterCSV.process(input, given_options = {}, &block) # rubocop:disable Lint
       @headers, header_size = process_headers(fh, options)
       @headerA = @headers # @headerA is deprecated, use @headers
 
+      puts "Effective headers:\n#{pp(@headers)}\n" if @verbose
+
+      header_validations(@headers, options)
+
       # in case we use chunking.. we'll need to set it up..
       if options[:chunk_size].to_i > 0
         use_chunks = true
@@ -46,31 +51,42 @@ def SmarterCSV.process(input, given_options = {}, &block) # rubocop:disable Lint
       end
 
       # now on to processing all the rest of the lines in the CSV file:
+      # fh.each_line |line|
       until fh.eof? # we can't use fh.readlines() here, because this would read the whole file into memory at once, and eof => true
         line = readline_with_counts(fh, options)
 
         # replace invalid byte sequence in UTF-8 with question mark to avoid errors
-        line = line.force_encoding('utf-8').encode('utf-8', invalid: :replace, undef: :replace, replace: options[:invalid_byte_sequence]) if options[:force_utf8] || options[:file_encoding] !~ /utf-8/i
+        line = enforce_utf8_encoding(line, options) if @enforce_utf8
 
-        print "processing file line %10d, csv line %10d\r" % [@file_line_count, @csv_line_count] if options[:verbose]
+        print "processing file line %10d, csv line %10d\r" % [@file_line_count, @csv_line_count] if @verbose
 
         next if options[:comment_regexp] && line =~ options[:comment_regexp] # ignore all comment lines if there are any
 
         # cater for the quoted csv data containing the row separator carriage return character
         # in which case the row data will be split across multiple lines (see the sample content in spec/fixtures/carriage_returns_rn.csv)
         # by detecting the existence of an uneven number of quote characters
+        multiline = count_quote_chars(line, options[:quote_char]).odd?
 
-        multiline = count_quote_chars(line, options[:quote_char]).odd? # should handle quote_char nil
-        while count_quote_chars(line, options[:quote_char]).odd? # should handle quote_char nil
+        while multiline
           next_line = fh.readline(options[:row_sep])
-          next_line = next_line.force_encoding('utf-8').encode('utf-8', invalid: :replace, undef: :replace, replace: options[:invalid_byte_sequence]) if options[:force_utf8] || options[:file_encoding] !~ /utf-8/i
+          next_line = enforce_utf8_encoding(next_line, options) if @enforce_utf8
           line += next_line
           @file_line_count += 1
+
+          break if fh.eof? # Exit loop if end of file is reached
+
+          multiline = count_quote_chars(line, options[:quote_char]).odd?
+        end
+
+        # :nocov:
+        if multiline && @verbose
+          print "\nline contains uneven number of quote chars so including content through file line %d\n" % @file_line_count
         end
-        print "\nline contains uneven number of quote chars so including content through file line %d\n" % @file_line_count if options[:verbose] && multiline
+        # :nocov:
 
         line.chomp!(options[:row_sep])
 
+        # --- SPLIT LINE & DATA TRANSFORMATIONS ------------------------------------------------------------
         dataA, _data_size = parse(line, options, header_size)
 
         dataA.map!{|x| x.strip} if options[:strip_whitespace]
@@ -78,48 +94,25 @@ def SmarterCSV.process(input, given_options = {}, &block) # rubocop:disable Lint
         # if all values are blank, then ignore this line
         next if options[:remove_empty_hashes] && (dataA.empty? || blank?(dataA))
 
+        # --- HASH TRANSFORMATIONS ------------------------------------------------------------
         hash = @headers.zip(dataA).to_h
 
-        # make sure we delete any key/value pairs from the hash, which the user wanted to delete:
-        hash.delete(nil)
-        hash.delete('')
-        hash.delete(:"")
+        hash = hash_transformations(hash, options)
 
-        if options[:remove_empty_values] == true
-          hash.delete_if{|_k, v| has_rails ? v.blank? : blank?(v)}
-        end
-
-        hash.delete_if{|_k, v| !v.nil? && v =~ /^(0+|0+\.0+)$/} if options[:remove_zero_values] # values are Strings
-        hash.delete_if{|_k, v| v =~ options[:remove_values_matching]} if options[:remove_values_matching]
-
-        if options[:convert_values_to_numeric]
-          hash.each do |k, v|
-            # deal with the :only / :except options to :convert_values_to_numeric
-            next if limit_execution_for_only_or_except(options, :convert_values_to_numeric, k)
-
-            # convert if it's a numeric value:
-            case v
-            when /^[+-]?\d+\.\d+$/
-              hash[k] = v.to_f
-            when /^[+-]?\d+$/
-              hash[k] = v.to_i
-            end
-          end
-        end
-
-        if options[:value_converters]
-          hash.each do |k, v|
-            converter = options[:value_converters][k]
-            next unless converter
-
-            hash[k] = converter.convert(v)
-          end
-        end
+        # --- HASH VALIDATIONS ----------------------------------------------------------------
+        # will go here, and be able to:
+        #  - validate correct format of the values for fields
+        #  - required fields to be non-empty
+        #  - ...
+        # -------------------------------------------------------------------------------------
 
         next if options[:remove_empty_hashes] && hash.empty?
 
+        puts "CSV Line #{@file_line_count}: #{pp(hash)}" if @verbose == '2' # very verbose setting
+        # optional adding of csv_line_number to the hash to help debugging
         hash[:csv_line_number] = @csv_line_count if options[:with_line_numbers]
 
+        # process the chunks or the resulting hash
         if use_chunks
           chunk << hash # append temp result to chunk
 
@@ -128,16 +121,13 @@ def SmarterCSV.process(input, given_options = {}, &block) # rubocop:disable Lint
             if block_given?
               yield chunk # do something with the hashes in the chunk in the block
             else
-              @result << chunk # not sure yet, why anybody would want to do this without a block
+              @result << chunk.dup # Append chunk to result (use .dup to keep a copy after we do chunk.clear)
             end
             @chunk_count += 1
-            chunk = [] # initialize for next chunk of data
+            chunk.clear # re-initialize for next chunk of data
           else
-
-            # the last chunk may contain partial data, which also needs to be returned (BUG / ISSUE-18)
-
+            # the last chunk may contain partial data, which is handled below
           end
-
           # while a chunk is being filled up we don't need to do anything else here
 
         else # no chunk handling
@@ -150,15 +140,15 @@ def SmarterCSV.process(input, given_options = {}, &block) # rubocop:disable Lint
       end
 
       # print new line to retain last processing line message
-      print "\n" if options[:verbose]
+      print "\n" if @verbose
 
-      # last chunk:
+      # handling of last chunk:
       if !chunk.nil? && chunk.size > 0
         # do something with the chunk
         if block_given?
           yield chunk # do something with the hashes in the chunk in the block
         else
-          @result << chunk # not sure yet, why anybody would want to do this without a block
+          @result << chunk.dup # Append chunk to result (use .dup to keep a copy after we do chunk.clear)
         end
         @chunk_count += 1
         # chunk = [] # initialize for next chunk of data
@@ -175,16 +165,22 @@ def SmarterCSV.process(input, given_options = {}, &block) # rubocop:disable Lint
   end
 
   class << self
-    # * the `scan` method iterates through the string and finds all occurrences of the pattern
-    # * The reqular expression:
-    #   - (?<!\\) : Negative lookbehind to ensure the quote character is not preceded by an unescaped backslash.
-    #   - (?:\\\\)* : Non-capturing group for an even number of backslashes (escaped backslashes).
-    #                 This allows for any number of escaped backslashes before the quote character.
-    #   - #{Regexp.escape(quote_char)} : Dynamically inserts the quote_char into the regex,
-    #                                    ensuring it's properly escaped for use in the regex.
-    #
     def count_quote_chars(line, quote_char)
-      line.scan(/(?<!\\)(?:\\\\)*#{Regexp.escape(quote_char)}/).count
+      return 0 if line.nil? || quote_char.nil? || quote_char.empty?
+
+      count = 0
+      escaped = false
+
+      line.each_char do |char|
+        if char == '\\' && !escaped
+          escaped = true
+        else
+          count += 1 if char == quote_char && !escaped
+          escaped = false
+        end
+      end
+
+      count
     end
 
     def has_acceleration?
@@ -193,18 +189,6 @@ def has_acceleration?
 
     protected
 
-    # acts as a road-block to limit processing when iterating over all k/v pairs of a CSV-hash:
-    def limit_execution_for_only_or_except(options, option_name, key)
-      if options[option_name].is_a?(Hash)
-        if options[option_name].has_key?(:except)
-          return true if Array(options[option_name][:except]).include?(key)
-        elsif options[option_name].has_key?(:only)
-          return true unless Array(options[option_name][:only]).include?(key)
-        end
-      end
-      false
-    end
-
     # SEE: https://github.com/rails/rails/blob/32015b6f369adc839c4f0955f2d9dce50c0b6123/activesupport/lib/active_support/core_ext/object/blank.rb#L121
     # and in the future we might also include UTF-8 space characters: https://www.compart.com/en/unicode/category/Zs
     BLANK_RE = /\A\s*\z/.freeze
@@ -212,33 +196,24 @@ def limit_execution_for_only_or_except(options, option_name, key)
     def blank?(value)
       case value
       when String
-        value.empty? || BLANK_RE.match?(value)
-
+        BLANK_RE.match?(value)
       when NilClass
         true
-
       when Array
-        value.empty? || value.inject(true){|result, x| result && elem_blank?(x)}
-
+        value.all? { |elem| blank?(elem) }
       when Hash
-        value.empty? || value.values.inject(true){|result, x| result && elem_blank?(x)}
-
+        value.values.all? { |elem| blank?(elem) } # Focus on values only
       else
         false
       end
     end
 
-    def elem_blank?(value)
-      case value
-      when String
-        value.empty? || BLANK_RE.match?(value)
+    private
 
-      when NilClass
-        true
+    def enforce_utf8_encoding(line, options)
+      # return line unless options[:force_utf8] || options[:file_encoding] !~ /utf-8/i
 
-      else
-        false
-      end
+      line.force_encoding('utf-8').encode('utf-8', invalid: :replace, undef: :replace, replace: options[:invalid_byte_sequence])
     end
   end
 end
diff --git a/lib/smarter_csv/variables.rb b/lib/smarter_csv/variables.rb
index 8f496304..1fa8a2c7 100644
--- a/lib/smarter_csv/variables.rb
+++ b/lib/smarter_csv/variables.rb
@@ -2,9 +2,10 @@
 
 module SmarterCSV
   class << self
-    attr_reader :csv_line_count, :chunk_count, :errors, :file_line_count, :headers, :raw_header, :result, :warnings
+    attr_reader :has_rails, :csv_line_count, :chunk_count, :errors, :file_line_count, :headers, :raw_header, :result, :warnings
 
     def initialize_variables
+      @has_rails = !!defined?(Rails)
       @csv_line_count = 0
       @chunk_count = 0
       @errors = {}
@@ -14,13 +15,16 @@ def initialize_variables
       @raw_header = nil # header as it appears in the file
       @result = []
       @warnings = {}
+      @enforce_utf8 = false # only set to true if needed (after options parsing)
     end
 
     # :nocov:
+    # rubocop:disable Naming/MethodName
     def headerA
       warn "Deprecarion Warning: 'headerA' will be removed in future versions. Use 'headders'"
       @headerA
     end
+    # rubocop:enable Naming/MethodName
     # :nocov:
   end
 end
diff --git a/lib/smarter_csv/version.rb b/lib/smarter_csv/version.rb
index 61b01dc4..ea86e60d 100644
--- a/lib/smarter_csv/version.rb
+++ b/lib/smarter_csv/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module SmarterCSV
-  VERSION = "1.9.3"
+  VERSION = "1.10.0"
 end
diff --git a/spec/smarter_csv/binary_file2_spec.rb b/spec/features/binary/binary_file_spec.rb
similarity index 53%
rename from spec/smarter_csv/binary_file2_spec.rb
rename to spec/features/binary/binary_file_spec.rb
index a69ab194..b7377e58 100644
--- a/spec/smarter_csv/binary_file2_spec.rb
+++ b/spec/features/binary/binary_file_spec.rb
@@ -8,12 +8,30 @@
 # but contains control characters delimiting the rows and columns, and also
 # contains a comment section which is commented our by a leading # character
 
-# same as binary_file_spec , but reading the file with strings as keys
+describe 'read binary files' do
+  let(:binary_file) { "#{fixture_path}/binary.csv" }
+
+  it 'loads_binary_file_with_comments' do
+    options = {col_sep: "\cA", row_sep: "\cB", comment_regexp: /^#/}
+    data = SmarterCSV.process(binary_file, options)
+    expect(data.flatten.size).to eq 8
+
+    data.each do |item|
+      # all keys should be symbols
+      item.each_key do |key|
+        expect(key.class).to eq Symbol
+      end
+      expect(item[:timestamp]).to eq 1_381_388_409
+      expect(item[:item_id].class).to eq Integer
+      expect(item[:name].size).to be > 0
+    end
+  end
+
+  # same as previous test, but reading the file with strings as keys
 
-describe 'be_able_to' do
   it 'loads_binary_file_with_strings_as_keys' do
     options = {col_sep: "\cA", row_sep: "\cB", comment_regexp: /^#/, strings_as_keys: true}
-    data = SmarterCSV.process("#{fixture_path}/binary.csv", options)
+    data = SmarterCSV.process(binary_file, options)
     expect(data.size).to eq 8
 
     data.each do |item|
diff --git a/spec/smarter_csv/chunked_reading_spec.rb b/spec/features/chunked/chunked_reading_spec.rb
similarity index 97%
rename from spec/smarter_csv/chunked_reading_spec.rb
rename to spec/features/chunked/chunked_reading_spec.rb
index ad73824c..95dd661b 100644
--- a/spec/smarter_csv/chunked_reading_spec.rb
+++ b/spec/features/chunked/chunked_reading_spec.rb
@@ -4,7 +4,7 @@
 
 fixture_path = 'spec/fixtures'
 
-describe 'be_able_to' do
+describe 'chunked reading' do
   it 'loads_chunk_cornercase_csv_files' do
     6.times do |chunk_size| # test for all chunk-sizes
       options = {chunk_size: chunk_size, remove_empty_hashes: true}
diff --git a/spec/smarter_csv/chunked_spec.rb b/spec/features/chunked/chunked_spec.rb
similarity index 100%
rename from spec/smarter_csv/chunked_spec.rb
rename to spec/features/chunked/chunked_spec.rb
diff --git a/spec/smarter_csv/convert_values_to_numeric_spec.rb b/spec/features/converters/convert_values_to_numeric_spec.rb
similarity index 100%
rename from spec/smarter_csv/convert_values_to_numeric_spec.rb
rename to spec/features/converters/convert_values_to_numeric_spec.rb
diff --git a/spec/smarter_csv/value_converters_spec.rb b/spec/features/converters/value_converters_spec.rb
similarity index 92%
rename from spec/smarter_csv/value_converters_spec.rb
rename to spec/features/converters/value_converters_spec.rb
index 905b88e2..abcd99fe 100644
--- a/spec/smarter_csv/value_converters_spec.rb
+++ b/spec/features/converters/value_converters_spec.rb
@@ -13,11 +13,11 @@ def self.convert(value)
 
 class CurrencyConverter
   def self.convert(value)
-    value.sub(/[$]/, '').to_f  # would be nice to add a computed column :currency => '€'
+    value.sub(/[$]/, '').to_f # would be nice to add a computed column :currency => '€'
   end
 end
 
-describe 'be_able_to' do
+describe ':value_converters option' do
   it 'convert date values into Date instances' do
     options = {value_converters: {date: DateConverter}}
     data = SmarterCSV.process("#{fixture_path}/with_dates.csv", options)
diff --git a/spec/smarter_csv/bom_issues_spec.rb b/spec/features/formating/bom_issues_spec.rb
similarity index 100%
rename from spec/smarter_csv/bom_issues_spec.rb
rename to spec/features/formating/bom_issues_spec.rb
diff --git a/spec/smarter_csv/carriage_return_spec.rb b/spec/features/formating/carriage_return_spec.rb
similarity index 100%
rename from spec/smarter_csv/carriage_return_spec.rb
rename to spec/features/formating/carriage_return_spec.rb
diff --git a/spec/smarter_csv/column_separator_spec.rb b/spec/features/formating/column_separator_spec.rb
similarity index 95%
rename from spec/smarter_csv/column_separator_spec.rb
rename to spec/features/formating/column_separator_spec.rb
index ae908127..6785ff15 100644
--- a/spec/smarter_csv/column_separator_spec.rb
+++ b/spec/features/formating/column_separator_spec.rb
@@ -171,14 +171,14 @@
           {
             col_sep: :auto,
             headers_in_file: false,
-            user_provided_headers: %w[Date1 Date2],
+            user_provided_headers: %w[Date1 Date2], # user provides strings
           }
         end
 
         it 'will fail to guess the separator' do
           data = SmarterCSV.process("#{fixture_path}/separator_comma_no_headers_will_fail.csv", options)
-          expect(data.first[:Date1]).to eq '2022-10-04 16' # Instead of 2022-10-04 16:00:47 UTC
-          expect(data.first[:Date2]).to eq 0 # Instead of 2022-10-04 16:00:47 UTC
+          expect(data.first['Date1']).to eq '2022-10-04 16' # Instead of 2022-10-04 16:00:47 UTC
+          expect(data.first['Date2']).to eq 0 # Instead of 2022-10-04 16:00:47 UTC
         end
       end
     end
diff --git a/spec/smarter_csv/emoji_spec.rb b/spec/features/formating/emoji_spec.rb
similarity index 100%
rename from spec/smarter_csv/emoji_spec.rb
rename to spec/features/formating/emoji_spec.rb
diff --git a/spec/smarter_csv/line_ending_spec.rb b/spec/features/formating/line_ending_spec.rb
similarity index 100%
rename from spec/smarter_csv/line_ending_spec.rb
rename to spec/features/formating/line_ending_spec.rb
diff --git a/spec/smarter_csv/valid_unicode_spec.rb b/spec/features/formating/valid_unicode_spec.rb
similarity index 99%
rename from spec/smarter_csv/valid_unicode_spec.rb
rename to spec/features/formating/valid_unicode_spec.rb
index fcd38d81..00493a29 100644
--- a/spec/smarter_csv/valid_unicode_spec.rb
+++ b/spec/features/formating/valid_unicode_spec.rb
@@ -4,7 +4,7 @@
 
 fixture_path = 'spec/fixtures'
 
-describe 'be_able_to' do
+describe 'valid unicode' do
   it 'loads file with unicode strings' do
     options = {}
     data = SmarterCSV.process("#{fixture_path}/valid_unicode.csv", options)
diff --git a/spec/smarter_csv/additional_separator_spec.rb b/spec/features/general/additional_separator_spec.rb
similarity index 100%
rename from spec/smarter_csv/additional_separator_spec.rb
rename to spec/features/general/additional_separator_spec.rb
diff --git a/spec/features/general/basic_spec.rb b/spec/features/general/basic_spec.rb
new file mode 100644
index 00000000..37b1eb5e
--- /dev/null
+++ b/spec/features/general/basic_spec.rb
@@ -0,0 +1,97 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+fixture_path = 'spec/fixtures'
+
+[true, false].each do |bool|
+  describe "fulfills basic tests with#{bool ? ' C-' : 'out '}acceleration" do
+    let(:options) { { acceleration: bool } }
+
+    describe 'basic CSV processing' do
+      # works only when testing locally
+      unless ENV['CI']
+        it 'compiles the acceleration' do
+          expect(SmarterCSV.has_acceleration?).to eq true
+        end
+      end
+
+      context 'with basic CSV file' do
+        let(:basic_file) { "#{fixture_path}/basic.csv" }
+
+        it 'loads_basic_csv_file' do
+          data = SmarterCSV.process(basic_file, options)
+          expect(data.size).to eq 5
+
+          data.each do |h|
+            h.each_key do |key|
+              # all the keys should be symbols
+              expect(key.class).to eq Symbol
+
+              expect(%i[first_name last_name dogs cats birds fish]).to include(key)
+            end
+            expect(h.size).to be <= 6
+          end
+        end
+
+        it 'loads_basic_csv_file from Rails' do
+          stub_const('Rails', true)
+          data = SmarterCSV.process(basic_file, options)
+          expect(data.size).to eq 5
+
+          data.each do |h|
+            h.each_key do |key|
+              # all the keys should be symbols
+              expect(key.class).to eq Symbol
+
+              expect(%i[first_name last_name dogs cats birds fish]).to include(key)
+            end
+            expect(h.size).to be <= 6
+          end
+        end
+
+        context 'with full user_provided_headers' do
+          let(:options) { super().merge({user_provided_headers: %i[a b c d e f]}) }
+
+          it 'replaces headers with user_provided_headers' do
+            data = SmarterCSV.process(basic_file, options)
+            expect(data.size).to eq 5
+
+            expect(SmarterCSV.raw_header).to eq "First Name,Last Name,Dogs,Cats,Birds,Fish\n"
+            expect(SmarterCSV.headers).to eq %i[a b c d e f]
+          end
+        end
+
+        context 'with partial user_provided_headers' do
+          let(:options) { super().merge({user_provided_headers: %i[a b c d e]}) }
+
+          it 'raises an exception if the number of user_provided_headers is incorrect' do
+            expect do
+              SmarterCSV.process(basic_file, options)
+            end.to raise_exception(SmarterCSV::HeaderSizeMismatch)
+          end
+        end
+
+        context 'with empty user_provided_headers' do
+          let(:options) { super().merge({user_provided_headers: []}) }
+
+          it 'raises an exception if the user_provided_headers is empty' do
+            expect do
+              SmarterCSV.process(basic_file, options)
+            end.to raise_exception(SmarterCSV::IncorrectOption, /ERROR: incorrect format for user_provided_headers! Expecting array with headers/)
+          end
+        end
+
+        context 'with incorrect user_provided_headers' do
+          let(:options) { super().merge({user_provided_headers: {}}) }
+
+          it 'raises an exception if the user_provided_headers is of incorrect type' do
+            expect do
+              SmarterCSV.process(basic_file, options)
+            end.to raise_exception(SmarterCSV::IncorrectOption, /ERROR: incorrect format for user_provided_headers! Expecting array with headers/)
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/smarter_csv/empty_columns_spec.rb b/spec/features/general/empty_columns_spec.rb
similarity index 100%
rename from spec/smarter_csv/empty_columns_spec.rb
rename to spec/features/general/empty_columns_spec.rb
diff --git a/spec/smarter_csv/simple_spec.rb b/spec/features/general/simple_spec.rb
similarity index 100%
rename from spec/smarter_csv/simple_spec.rb
rename to spec/features/general/simple_spec.rb
diff --git a/spec/smarter_csv/remove_empty_values_spec.rb b/spec/features/hash_transformations/remove_empty_values_spec.rb
similarity index 81%
rename from spec/smarter_csv/remove_empty_values_spec.rb
rename to spec/features/hash_transformations/remove_empty_values_spec.rb
index 02c2e30d..788eb826 100644
--- a/spec/smarter_csv/remove_empty_values_spec.rb
+++ b/spec/features/hash_transformations/remove_empty_values_spec.rb
@@ -4,8 +4,8 @@
 
 fixture_path = 'spec/fixtures'
 
-describe 'be_able_to' do
-  it 'remove_empty_values' do
+describe ':remove_empty_values option' do
+  it 'removes empty values' do
     options = {row_sep: :auto, remove_empty_values: true}
     data = SmarterCSV.process("#{fixture_path}/empty.csv", options)
     expect(data.size).to eq 1
diff --git a/spec/smarter_csv/remove_keys_from_hashes_spec.rb b/spec/features/hash_transformations/remove_keys_from_hashes_spec.rb
similarity index 77%
rename from spec/smarter_csv/remove_keys_from_hashes_spec.rb
rename to spec/features/hash_transformations/remove_keys_from_hashes_spec.rb
index 1e1b2d96..065920b2 100644
--- a/spec/smarter_csv/remove_keys_from_hashes_spec.rb
+++ b/spec/features/hash_transformations/remove_keys_from_hashes_spec.rb
@@ -4,8 +4,8 @@
 
 fixture_path = 'spec/fixtures'
 
-describe 'be_able_to' do
-  it 'remove_values_matching' do
+describe ':remove_zero_values option' do
+  it 'removes zero values' do
     options = {remove_zero_values: true, key_mapping: {first_name: :vorname, last_name: :nachname, fish: nil} }
     data = SmarterCSV.process("#{fixture_path}/basic.csv", options)
     expect(data.size).to eq 5
@@ -16,7 +16,8 @@
 
         expect(%i[vorname nachname dogs cats birds]).to include(key)
       end
-      expect(hash.values).to_not include(0)
+      expect(hash.keys).not_to include(:fish)
+      expect(hash.values).not_to include(0)
 
       expect(hash.size).to be <= 6
     end
diff --git a/spec/smarter_csv/remove_not_mapped_keys_spec.rb b/spec/features/hash_transformations/remove_not_mapped_keys_spec.rb
similarity index 100%
rename from spec/smarter_csv/remove_not_mapped_keys_spec.rb
rename to spec/features/hash_transformations/remove_not_mapped_keys_spec.rb
diff --git a/spec/smarter_csv/remove_values_matching_spec.rb b/spec/features/hash_transformations/remove_values_matching_spec.rb
similarity index 85%
rename from spec/smarter_csv/remove_values_matching_spec.rb
rename to spec/features/hash_transformations/remove_values_matching_spec.rb
index 112aa032..7484dd3a 100644
--- a/spec/smarter_csv/remove_values_matching_spec.rb
+++ b/spec/features/hash_transformations/remove_values_matching_spec.rb
@@ -4,8 +4,8 @@
 
 fixture_path = 'spec/fixtures'
 
-describe 'be_able_to' do
-  it 'remove_values_matching' do
+describe ':remove_values_matching option' do
+  it 'removes values' do
     options = {remove_zero_values: true, remove_empty_values: true, remove_values_matching: /^\d+$/}
     data = SmarterCSV.process("#{fixture_path}/basic.csv", options)
     expect(data.size).to eq 5
@@ -21,7 +21,7 @@
         expect(val.class).to eq String # all the values should be strings
       end
 
-      expect(hash.values).to_not include(0)
+      expect(hash.values).not_to include(0)
 
       expect(hash.size).to be <= 6
     end
diff --git a/spec/smarter_csv/remove_zero_values_spec.rb b/spec/features/hash_transformations/remove_zero_values_spec.rb
similarity index 81%
rename from spec/smarter_csv/remove_zero_values_spec.rb
rename to spec/features/hash_transformations/remove_zero_values_spec.rb
index 50307213..7aa07c0d 100644
--- a/spec/smarter_csv/remove_zero_values_spec.rb
+++ b/spec/features/hash_transformations/remove_zero_values_spec.rb
@@ -4,8 +4,8 @@
 
 fixture_path = 'spec/fixtures'
 
-describe 'be_able_to' do
-  it 'remove_zero_values' do
+describe ':remove_zero_values option' do
+  it 'removes zero values' do
     options = {remove_zero_values: true, remove_empty_values: true}
     data = SmarterCSV.process("#{fixture_path}/basic.csv", options)
     expect(data.size).to eq 5
@@ -17,7 +17,7 @@
         expect(%i[first_name last_name dogs cats birds fish]).to include(key)
       end
 
-      expect(hash.values).to_not include(0)
+      expect(hash.values).not_to include(0)
 
       expect(hash.size).to be <= 6
     end
diff --git a/spec/smarter_csv/duplicate_headers_spec.rb b/spec/features/header_handling/duplicate_headers_spec.rb
similarity index 61%
rename from spec/smarter_csv/duplicate_headers_spec.rb
rename to spec/features/header_handling/duplicate_headers_spec.rb
index 22d0cf00..f11c7dde 100644
--- a/spec/smarter_csv/duplicate_headers_spec.rb
+++ b/spec/features/header_handling/duplicate_headers_spec.rb
@@ -6,35 +6,37 @@
 
 describe 'duplicate headers' do
   describe 'without special handling / default behavior' do
-    it 'raises error on duplicate headers' do
-      expect do
-        SmarterCSV.process("#{fixture_path}/duplicate_headers.csv", {})
-      end.to raise_exception(SmarterCSV::DuplicateHeaders)
-    end
-
     it 'does not raise error when duplicate_header_suffix is given' do
       expect do
         SmarterCSV.process("#{fixture_path}/duplicate_headers.csv", {duplicate_header_suffix: ''})
       end.not_to raise_exception
     end
 
-    it 'does not raise error when user_provided_headers are given' do
+    it 'raises error when user_provided_headers with duplicates are given' do
       expect do
         options = {user_provided_headers: %i[a b c d a]}
         SmarterCSV.process("#{fixture_path}/duplicate_headers.csv", options)
-      end.not_to raise_exception
+      end.to raise_exception(SmarterCSV::DuplicateHeaders)
     end
 
-    it 'raises error on duplicate headers, when attempting to do key_mapping' do
-      # the mapping is right, but the underlying csv file is bad
-      options = {key_mapping: {email: :a, firstname: :b, lastname: :c, age: :e} }
-      expect do
-        SmarterCSV.process("#{fixture_path}/duplicate_headers.csv", options)
-      end.to raise_exception(SmarterCSV::DuplicateHeaders)
+    it 'can remap duplicated headers' do
+      options ={key_mapping: {email: :a, firstname: :b, lastname: :c, email2: :d, age: :e}}
+      data = SmarterCSV.process("#{fixture_path}/duplicate_headers.csv", options)
+      expect(data.first).to eq({a: 'tom@bla.com', b: 'Tom', c: 'Sawyer', d: 'mike@bla.com', e: 34})
     end
   end
 
   describe 'with special handling' do
+    context 'when suffix is set to nil' do
+      let(:options) { {duplicate_header_suffix: nil} }
+
+      it 'raises error on duplicate headers in the input file' do
+        expect do
+          SmarterCSV.process("#{fixture_path}/duplicate_headers.csv", options)
+        end.to raise_exception(SmarterCSV::DuplicateHeaders)
+      end
+    end
+
     context 'with given suffix' do
       let(:options) { {duplicate_header_suffix: '_'} }
 
@@ -48,10 +50,11 @@
         expect(data.first.keys).to eq %i[email firstname lastname email_2 age]
       end
 
-      it 'enumerates when duplicate headers are given' do
+      it 'raises when duplicate headers are given' do
         options.merge!({user_provided_headers: %i[a b c a a]})
-        data = SmarterCSV.process("#{fixture_path}/duplicate_headers.csv", options)
-        expect(data.first.keys).to eq %i[a b c a_2 a_3]
+        expect do
+          SmarterCSV.process("#{fixture_path}/duplicate_headers.csv", options)
+        end.to raise_exception(SmarterCSV::DuplicateHeaders)
       end
 
       it 'can remap duplicated headers' do
@@ -61,8 +64,8 @@
       end
     end
 
-    context 'with empty suffix' do
-      let(:options) { {duplicate_header_suffix: ''} }
+    context 'with different suffix' do
+      let(:options) { {duplicate_header_suffix: ':'} }
 
       it 'reads whole file' do
         data = SmarterCSV.process("#{fixture_path}/duplicate_headers.csv", options)
@@ -71,13 +74,14 @@
 
       it 'generates the correct keys' do
         data = SmarterCSV.process("#{fixture_path}/duplicate_headers.csv", options)
-        expect(data.first.keys).to eq %i[email firstname lastname email2 age]
+        expect(data.first.keys).to eq %i[email firstname lastname email:2 age]
       end
 
-      it 'enumerates when duplicate headers are given' do
+      it 'raises when duplicate headers are given' do
         options.merge!({user_provided_headers: %i[a b c a a]})
-        data = SmarterCSV.process("#{fixture_path}/duplicate_headers.csv", options)
-        expect(data.first.keys).to eq %i[a b c a2 a3]
+        expect do
+          SmarterCSV.process("#{fixture_path}/duplicate_headers.csv", options)
+        end.to raise_exception(SmarterCSV::DuplicateHeaders)
       end
     end
   end
diff --git a/spec/smarter_csv/header_transformation_spec.rb b/spec/features/header_handling/header_transformation_spec.rb
similarity index 96%
rename from spec/smarter_csv/header_transformation_spec.rb
rename to spec/features/header_handling/header_transformation_spec.rb
index 94c25074..4a704639 100644
--- a/spec/smarter_csv/header_transformation_spec.rb
+++ b/spec/features/header_handling/header_transformation_spec.rb
@@ -4,7 +4,7 @@
 
 fixture_path = 'spec/fixtures'
 
-describe 'be_able_to' do
+describe 'header transformations option' do
   it 'loads_file_with_dashes_in_header_fields as strings' do
     options = {strings_as_keys: true}
     data = SmarterCSV.process("#{fixture_path}/with_dashes.csv", options)
diff --git a/spec/smarter_csv/invalid_headers_spec.rb b/spec/features/header_handling/invalid_headers_spec.rb
similarity index 65%
rename from spec/smarter_csv/invalid_headers_spec.rb
rename to spec/features/header_handling/invalid_headers_spec.rb
index 9ce05414..420b7877 100644
--- a/spec/smarter_csv/invalid_headers_spec.rb
+++ b/spec/features/header_handling/invalid_headers_spec.rb
@@ -60,35 +60,30 @@
   context 'mapping_keys: exception for missing keys / header names' do
     subject(:process_file) { SmarterCSV.process("#{fixture_path}/user_import.csv", options) }
 
-    let(:options) do
-      {
-        required_keys: [:middle_name],
-        key_mapping: { missing_key: :middle_name},
-      }
-    end
-
-    # we do not expect version 1.8 behavior:
-    it 'does not raise about the mapped header name when source of key_mapping is missing' do
-      expect(SmarterCSV).not_to receive(:puts).with a_string_matching(/WARNING.*missing_key/)
-      expect{ process_file }.not_to raise_exception(
-        SmarterCSV::MissingKeys, "ERROR: missing attributes: middle_name"
-      )
-    end
+    context 'when one key_mapping key is missing' do
+      let(:options) do
+        {
+          required_keys: [:middle_name],
+          key_mapping: { missing_key: :middle_name},
+        }
+      end
 
-    # we expect version 1.9 behavior:
-    it 'raises exception that the header for the key mapping is missing in the file' do
-      expect(SmarterCSV).not_to receive(:puts).with a_string_matching(/WARNING.*missing_key/)
-      expect{ process_file }.to raise_exception(
-        SmarterCSV::KeyMappingError, "ERROR: can not map headers: missing_key"
-      )
+      it 'raises exception that header for the key mapping is missing in file' do
+        expect(SmarterCSV).not_to receive(:puts).with a_string_matching(/WARNING.*missing_key/)
+        # we do not expect version 1.8 behavior:
+        expect{ process_file }.not_to raise_exception(
+          SmarterCSV::MissingKeys, "ERROR: missing attributes: middle_name"
+        )
+        # we expect version 1.9 behavior:
+        expect{ process_file }.to raise_exception(
+          SmarterCSV::KeyMappingError, "ERROR: can not map headers: missing_key"
+        )
+      end
     end
 
     context "when multiple keys are missing" do
       let(:options) do
-        {
-          required_keys: [:middle_name],
-          key_mapping: { missing_key: :middle_name, other_missing_key: :other },
-        }
+        { key_mapping: { missing_key: :middle_name, other_missing_key: :other } }
       end
 
       it 'raises exception that headers for the key mapping are missing in the file' do
@@ -97,30 +92,52 @@
           SmarterCSV::KeyMappingError, "ERROR: can not map headers: missing_key, other_missing_key"
         )
       end
-    end
 
-    context "when slience_missing_keys is used" do
-      it "does not raise an exception when :silence_missing_keys is true" do
+      it "does not raise any exception when :silence_missing_keys is true" do
         options[:silence_missing_keys] = true
         expect(SmarterCSV).not_to receive(:puts).with a_string_matching(/WARNING.*missing_key/)
-        expect{ process_file }.not_to raise_exception(
-          SmarterCSV::KeyMappingError,  "ERROR: can not map headers: missing_key"
-        )
+        expect{ process_file }.not_to raise_exception
+      end
+    end
+
+    context "when slience_missing_keys is used" do
+      let(:options) do
+        {
+          required_keys: [:middle_name],
+          key_mapping: { missing_key: :middle_name, other_optional_key: :other },
+        }
+      end
+
+      context "when invalid key_mapping is given" do
+        it "does not raise a KeyMappingError exception when :silence_missing_keys is true" do
+          options[:silence_missing_keys] = true
+          expect(SmarterCSV).not_to receive(:puts).with a_string_matching(/WARNING.*missing_key/)
+          expect{ process_file }.not_to raise_exception SmarterCSV::KeyMappingError
+          # still raises an error because :middle_name is required
+          expect{ process_file }.to raise_exception(
+            SmarterCSV::MissingKeys, "ERROR: missing attributes: middle_name"
+          )
+        end
       end
 
       it "does not raise an exception when :silence_missing_keys is an array containing the missing key" do
         options[:silence_missing_keys] = [:missing_key, :other_optional_key]
         expect(SmarterCSV).not_to receive(:puts).with a_string_matching(/WARNING.*missing_key/)
         expect{ process_file }.not_to raise_exception(
-          SmarterCSV::KeyMappingError,  "ERROR: can not map headers: missing_key"
+          SmarterCSV::KeyMappingError, "ERROR: can not map headers: missing_key"
+        )
+        # still raises an error because :middle_name is required
+        expect{ process_file }.to raise_exception(
+          SmarterCSV::MissingKeys, "ERROR: missing attributes: middle_name"
         )
       end
 
       it "raises an exception when :silence_missing_keys is an array but does not contain the missing key" do
         options[:silence_missing_keys] = [:other_optional_key]
         expect(SmarterCSV).not_to receive(:puts).with a_string_matching(/WARNING.*missing_key/)
+        # raises KeyMappingError because :missing_key is required:
         expect{ process_file }.to raise_exception(
-          SmarterCSV::KeyMappingError,  "ERROR: can not map headers: missing_key"
+          SmarterCSV::KeyMappingError, "ERROR: can not map headers: missing_key"
         )
       end
     end
diff --git a/spec/smarter_csv/keep_headers_spec.rb b/spec/features/header_handling/keep_headers_spec.rb
similarity index 92%
rename from spec/smarter_csv/keep_headers_spec.rb
rename to spec/features/header_handling/keep_headers_spec.rb
index c26c31d9..f2d6a5d9 100644
--- a/spec/smarter_csv/keep_headers_spec.rb
+++ b/spec/features/header_handling/keep_headers_spec.rb
@@ -4,7 +4,7 @@
 
 fixture_path = 'spec/fixtures'
 
-describe 'be_able_to' do
+describe ':keep_original_headers option' do
   it 'not_downcase_headers' do
     options = {keep_original_headers: true}
     data = SmarterCSV.process("#{fixture_path}/basic.csv", options)
diff --git a/spec/smarter_csv/key_mapping_spec.rb b/spec/features/header_handling/key_mapping_spec.rb
similarity index 100%
rename from spec/smarter_csv/key_mapping_spec.rb
rename to spec/features/header_handling/key_mapping_spec.rb
diff --git a/spec/smarter_csv/no_header_spec.rb b/spec/features/header_handling/no_header_spec.rb
similarity index 100%
rename from spec/smarter_csv/no_header_spec.rb
rename to spec/features/header_handling/no_header_spec.rb
diff --git a/spec/smarter_csv/not_downcase_header_spec.rb b/spec/features/header_handling/not_downcase_header_spec.rb
similarity index 93%
rename from spec/smarter_csv/not_downcase_header_spec.rb
rename to spec/features/header_handling/not_downcase_header_spec.rb
index 7787206a..2124a718 100644
--- a/spec/smarter_csv/not_downcase_header_spec.rb
+++ b/spec/features/header_handling/not_downcase_header_spec.rb
@@ -4,7 +4,7 @@
 
 fixture_path = 'spec/fixtures'
 
-describe 'be_able_to' do
+describe ':downcase_header option' do
   it 'not_downcase_headers' do
     options = {downcase_header: false}
     data = SmarterCSV.process("#{fixture_path}/basic.csv", options)
diff --git a/spec/smarter_csv/required_headers_spec.rb b/spec/features/header_handling/required_headers_spec.rb
similarity index 100%
rename from spec/smarter_csv/required_headers_spec.rb
rename to spec/features/header_handling/required_headers_spec.rb
diff --git a/spec/smarter_csv/silence_missing_keys_spec.rb b/spec/features/header_handling/silence_missing_keys_spec.rb
similarity index 100%
rename from spec/smarter_csv/silence_missing_keys_spec.rb
rename to spec/features/header_handling/silence_missing_keys_spec.rb
diff --git a/spec/smarter_csv/strings_as_keys_spec.rb b/spec/features/header_handling/strings_as_keys_spec.rb
similarity index 86%
rename from spec/smarter_csv/strings_as_keys_spec.rb
rename to spec/features/header_handling/strings_as_keys_spec.rb
index dc2b2ff2..5bf1266d 100644
--- a/spec/smarter_csv/strings_as_keys_spec.rb
+++ b/spec/features/header_handling/strings_as_keys_spec.rb
@@ -4,8 +4,8 @@
 
 fixture_path = 'spec/fixtures'
 
-describe 'be_able_to' do
-  it 'use_strings_as_keys' do
+describe ':strings_as_keys option' do
+  it 'uses strings as hash keys' do
     options = {strings_as_keys: true}
     data = SmarterCSV.process("#{fixture_path}/basic.csv", options)
     expect(data.size).to eq 5
diff --git a/spec/smarter_csv/strip_chars_from_headers_spec.rb b/spec/features/header_handling/strip_chars_from_headers_spec.rb
similarity index 84%
rename from spec/smarter_csv/strip_chars_from_headers_spec.rb
rename to spec/features/header_handling/strip_chars_from_headers_spec.rb
index fecafc78..db904d73 100644
--- a/spec/smarter_csv/strip_chars_from_headers_spec.rb
+++ b/spec/features/header_handling/strip_chars_from_headers_spec.rb
@@ -4,8 +4,8 @@
 
 fixture_path = 'spec/fixtures'
 
-describe 'be_able_to' do
-  it 'strip_whitespace_from_headers' do
+describe ':strip_chars_from_headers option' do
+  it 'strips whitespece from headers' do
     options = {strip_chars_from_headers: ' '}
     data = SmarterCSV.process("#{fixture_path}/basic.csv", options)
     expect(data.size).to eq 5
diff --git a/spec/smarter_csv/ignore_comments_spec.rb b/spec/features/ignore_comments_spec.rb
similarity index 97%
rename from spec/smarter_csv/ignore_comments_spec.rb
rename to spec/features/ignore_comments_spec.rb
index 3e48158d..956774a5 100644
--- a/spec/smarter_csv/ignore_comments_spec.rb
+++ b/spec/features/ignore_comments_spec.rb
@@ -4,7 +4,7 @@
 
 fixture_path = 'spec/fixtures'
 
-describe 'be_able_to' do
+describe ':comment_regexp option' do
   it 'by default does not ignore comments in CSV files' do
     options = {}
     data = SmarterCSV.process("#{fixture_path}/ignore_comments.csv", options)
diff --git a/spec/smarter_csv/escaped_quote_chars_spec.rb b/spec/features/quotes/escaped_quote_chars_spec.rb
similarity index 100%
rename from spec/smarter_csv/escaped_quote_chars_spec.rb
rename to spec/features/quotes/escaped_quote_chars_spec.rb
diff --git a/spec/smarter_csv/quoted_spec.rb b/spec/features/quotes/quoted_spec.rb
similarity index 96%
rename from spec/smarter_csv/quoted_spec.rb
rename to spec/features/quotes/quoted_spec.rb
index 41acc05a..4ee627a3 100644
--- a/spec/smarter_csv/quoted_spec.rb
+++ b/spec/features/quotes/quoted_spec.rb
@@ -20,8 +20,8 @@
       expect(data[3][:description]).to eq 'MUST SELL! air, moon roof, loaded'
       data.each do |h|
         expect(h[:year].class).to eq Integer
-        expect(h[:make]).to_not be_nil
-        expect(h[:model]).to_not be_nil
+        expect(h[:make]).not_to be_nil
+        expect(h[:model]).not_to be_nil
         expect(h[:price].class).to eq Float
       end
     end
diff --git a/spec/smarter_csv/skip_lines_spec.rb b/spec/features/skip_lines_spec.rb
similarity index 95%
rename from spec/smarter_csv/skip_lines_spec.rb
rename to spec/features/skip_lines_spec.rb
index d37a4ab1..6b19e380 100644
--- a/spec/smarter_csv/skip_lines_spec.rb
+++ b/spec/features/skip_lines_spec.rb
@@ -4,7 +4,7 @@
 
 fixture_path = 'spec/fixtures'
 
-describe 'be_able_to' do
+describe ':skip_lines option' do
   it 'loads_csv_file_skipping_lines' do
     options = {skip_lines: 3}
     data = SmarterCSV.process("#{fixture_path}/skip_lines.csv", options)
diff --git a/spec/smarter_csv/hard_sample_spec.rb b/spec/features/special_cases/hard_sample_spec.rb
similarity index 100%
rename from spec/smarter_csv/hard_sample_spec.rb
rename to spec/features/special_cases/hard_sample_spec.rb
diff --git a/spec/smarter_csv/malformed_spec.rb b/spec/features/special_cases/malformed_spec.rb
similarity index 100%
rename from spec/smarter_csv/malformed_spec.rb
rename to spec/features/special_cases/malformed_spec.rb
diff --git a/spec/smarter_csv/problematic_spec.rb b/spec/features/special_cases/problematic_spec.rb
similarity index 100%
rename from spec/smarter_csv/problematic_spec.rb
rename to spec/features/special_cases/problematic_spec.rb
diff --git a/spec/smarter_csv/trading_spec.rb b/spec/features/special_cases/trading_spec.rb
similarity index 100%
rename from spec/smarter_csv/trading_spec.rb
rename to spec/features/special_cases/trading_spec.rb
diff --git a/spec/smarter_csv/basic_spec.rb b/spec/smarter_csv/basic_spec.rb
deleted file mode 100644
index d10f65b7..00000000
--- a/spec/smarter_csv/basic_spec.rb
+++ /dev/null
@@ -1,93 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-
-fixture_path = 'spec/fixtures'
-
-[true, false].each do |bool|
-  describe "fulfills basic tests with#{bool ? ' C-' : 'out '}acceleration" do
-    let(:options) { { acceleration: bool } }
-
-    describe 'basic CSV processing' do
-      # works only when testing locally
-      unless ENV['CI']
-        it 'compiles the acceleration' do
-          expect(SmarterCSV.has_acceleration?).to eq true
-        end
-      end
-
-      it 'loads_basic_csv_file' do
-        data = SmarterCSV.process("#{fixture_path}/basic.csv", options)
-        expect(data.size).to eq 5
-
-        data.each do |h|
-          h.each_key do |key|
-            # all the keys should be symbols
-            expect(key.class).to eq Symbol
-
-            expect(%i[first_name last_name dogs cats birds fish]).to include(key)
-          end
-          expect(h.size).to be <= 6
-        end
-      end
-
-      it 'loads_basic_csv_file from Rails' do
-        stub_const('Rails', true)
-        data = SmarterCSV.process("#{fixture_path}/basic.csv", options)
-        expect(data.size).to eq 5
-
-        data.each do |h|
-          h.each_key do |key|
-            # all the keys should be symbols
-            expect(key.class).to eq Symbol
-
-            expect(%i[first_name last_name dogs cats birds fish]).to include(key)
-          end
-          expect(h.size).to be <= 6
-        end
-      end
-
-      context 'with full user_provided_headers' do
-        let(:options) { super().merge({user_provided_headers: %i[a b c d e f]}) }
-
-        it 'replaces headers with user_provided_headers' do
-          data = SmarterCSV.process("#{fixture_path}/basic.csv", options)
-          expect(data.size).to eq 5
-
-          expect(SmarterCSV.raw_header).to eq "First Name,Last Name,Dogs,Cats,Birds,Fish\n"
-          expect(SmarterCSV.headers).to eq %i[a b c d e f]
-        end
-      end
-
-      context 'with partial user_provided_headers' do
-        let(:options) { super().merge({user_provided_headers: %i[a b c d e]}) }
-
-        it 'raises an exception if the number of user_provided_headers is incorrect' do
-          expect do
-            SmarterCSV.process("#{fixture_path}/basic.csv", options)
-          end.to raise_exception(SmarterCSV::HeaderSizeMismatch)
-        end
-      end
-
-      context 'with empty user_provided_headers' do
-        let(:options) { super().merge({user_provided_headers: []}) }
-
-        it 'raises an exception if the user_provided_headers is empty' do
-          expect do
-            SmarterCSV.process("#{fixture_path}/basic.csv", options)
-          end.to raise_exception(SmarterCSV::IncorrectOption, /ERROR: incorrect format for user_provided_headers! Expecting array with headers/)
-        end
-      end
-
-      context 'with incorrect user_provided_headers' do
-        let(:options) { super().merge({user_provided_headers: {}}) }
-
-        it 'raises an exception if the user_provided_headers is of incorrect type' do
-          expect do
-            SmarterCSV.process("#{fixture_path}/basic.csv", options)
-          end.to raise_exception(SmarterCSV::IncorrectOption, /ERROR: incorrect format for user_provided_headers! Expecting array with headers/)
-        end
-      end
-    end
-  end
-end
diff --git a/spec/smarter_csv/binary_file_spec.rb b/spec/smarter_csv/binary_file_spec.rb
deleted file mode 100644
index a9513fba..00000000
--- a/spec/smarter_csv/binary_file_spec.rb
+++ /dev/null
@@ -1,27 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-
-fixture_path = 'spec/fixtures'
-
-# this reads a binary database dump file, which is in structure like a CSV file
-# but contains control characters delimiting the rows and columns, and also
-# contains a comment section which is commented our by a leading # character
-
-describe 'be_able_to' do
-  it 'loads_binary_file_with_comments' do
-    options = {col_sep: "\cA", row_sep: "\cB", comment_regexp: /^#/}
-    data = SmarterCSV.process("#{fixture_path}/binary.csv", options)
-    expect(data.flatten.size).to eq 8
-
-    data.each do |item|
-      # all keys should be symbols
-      item.each_key do |key|
-        expect(key.class).to eq Symbol
-      end
-      expect(item[:timestamp]).to eq 1_381_388_409
-      expect(item[:item_id].class).to eq Integer
-      expect(item[:name].size).to be > 0
-    end
-  end
-end
diff --git a/spec/smarter_csv/close_file_spec.rb b/spec/smarter_csv/close_file_spec.rb
index 97c4e7f2..cf6b6eb8 100644
--- a/spec/smarter_csv/close_file_spec.rb
+++ b/spec/smarter_csv/close_file_spec.rb
@@ -4,7 +4,7 @@
 
 fixture_path = 'spec/fixtures'
 
-describe 'be_able_to' do
+describe 'file operations' do
   it 'close file after using it' do
     options = {col_sep: "\cA", row_sep: "\cB", comment_regexp: /^#/, strings_as_keys: true}
 
diff --git a/spec/smarter_csv/misc_spec.rb b/spec/smarter_csv/misc_spec.rb
deleted file mode 100644
index 353f4597..00000000
--- a/spec/smarter_csv/misc_spec.rb
+++ /dev/null
@@ -1,27 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-
-describe 'misc functionality' do
-  describe 'elem_blank?' do
-    it 'returns true for nil' do
-      expect(SmarterCSV.send(:elem_blank?, nil)).to eq true
-    end
-
-    it 'returns true for ""' do
-      expect(SmarterCSV.send(:elem_blank?, "")).to eq true
-    end
-
-    it 'returns true for "\t \r\n\t"' do
-      expect(SmarterCSV.send(:elem_blank?, "\t \r\n\t")).to eq true
-    end
-
-    it 'returns false for "a"' do
-      expect(SmarterCSV.send(:elem_blank?, "a")).to eq false
-    end
-
-    it 'returns false for 1234' do
-      expect(SmarterCSV.send(:elem_blank?, 1234)).to eq false
-    end
-  end
-end
diff --git a/spec/smarter_csv/validations_spec.rb b/spec/smarter_csv/option_validations_spec.rb
similarity index 95%
rename from spec/smarter_csv/validations_spec.rb
rename to spec/smarter_csv/option_validations_spec.rb
index 6d2c3a04..9f070944 100644
--- a/spec/smarter_csv/validations_spec.rb
+++ b/spec/smarter_csv/option_validations_spec.rb
@@ -4,7 +4,7 @@
 
 fixture_path = 'spec/fixtures'
 
-describe 'validations' do
+describe 'option validations' do
   let(:options) { {} }
 
   it 'loads basic csv file without issues' do
diff --git a/spec/smarter_csv/options_processing_spec.rb b/spec/smarter_csv/options_processing_spec.rb
index 816746e2..61b65732 100644
--- a/spec/smarter_csv/options_processing_spec.rb
+++ b/spec/smarter_csv/options_processing_spec.rb
@@ -31,31 +31,29 @@
   end
 
   describe '#validate_options!' do
-    it 'raises an exception for row_sep' do
-      expect do
-        invalid_options = {
-          row_sep: nil,
-        }
-        SmarterCSV.process_options(invalid_options)
-      end.to raise_exception(SmarterCSV::ValidationError, '["invalid row_sep"]')
-    end
-
-    it 'raises an exception for col_sep' do
-      expect do
-        invalid_options = {
-          col_sep: nil,
-        }
-        SmarterCSV.process_options(invalid_options)
-      end.to raise_exception(SmarterCSV::ValidationError, '["invalid col_sep"]')
-    end
+    [:row_sep, :col_sep, :quote_char].each do |opt|
+      # empty values
+      [nil, ''].each do |val|
+        context "with invalid value #{val}" do
+          it "raises an exception for #{opt} set #{val}" do
+            expect do
+              invalid_options = {
+                opt => val,
+              }
+              SmarterCSV.process_options(invalid_options)
+            end.to raise_exception(SmarterCSV::ValidationError, "[\"invalid #{opt}\"]")
+          end
+        end
+      end
 
-    it 'raises an exception for quote_char' do
-      expect do
-        invalid_options = {
-          quote_char: nil,
-        }
-        SmarterCSV.process_options(invalid_options)
-      end.to raise_exception(SmarterCSV::ValidationError, '["invalid quote_char"]')
+      it "does not raise an exception for #{opt} set non-empty" do
+        expect do
+          invalid_options = {
+            opt => ' ',
+          }
+          SmarterCSV.process_options(invalid_options)
+        end.not_to raise_exception
+      end
     end
   end
 
diff --git a/spec/smarter_csv/parse/README.md b/spec/smarter_csv/parse/README.md
index e3c7dccc..6ef50f30 100644
--- a/spec/smarter_csv/parse/README.md
+++ b/spec/smarter_csv/parse/README.md
@@ -5,4 +5,6 @@ when testing `parse` methods:
   
 * make sure to always pass all options to the 'parse' methods, incl. acceleration
 
-* always wrap tests, so that both accelerated and un-accelerated code-paths are run
+* always wrap tests, so that both accelerated and un-accelerated code-paths are run, 
+  because the purpose of these tests is to ensure that both accelerated and unaccelerated 
+  code paths are behaving identically.
diff --git a/spec/smarter_csv/parse/column_separator_spec.rb b/spec/smarter_csv/parse/column_separator_spec.rb
index c813862c..eb8ecaf4 100644
--- a/spec/smarter_csv/parse/column_separator_spec.rb
+++ b/spec/smarter_csv/parse/column_separator_spec.rb
@@ -1,5 +1,17 @@
 # frozen_string_literal: true
 
+# ------------------------------------------------------------------------------------------
+# when testing `parse` methods:
+#
+# * SmarterCSV.default_options are not loaded when testing `parse` methods by themselves
+#
+# * make sure to always pass all options to the 'parse' methods, incl. acceleration
+#
+# * always wrap tests, so that both accelerated and un-accelerated code-paths are run,
+#   because the purpose of these tests is to ensure that both accelerated and unaccelerated
+#   code paths are behaving identically.
+# ------------------------------------------------------------------------------------------
+
 require 'spec_helper'
 
 [true, false].each do |bool|
diff --git a/spec/smarter_csv/parse/max_size_spec.rb b/spec/smarter_csv/parse/max_size_spec.rb
index c4f8ce33..fa2f7e44 100644
--- a/spec/smarter_csv/parse/max_size_spec.rb
+++ b/spec/smarter_csv/parse/max_size_spec.rb
@@ -1,5 +1,17 @@
 # frozen_string_literal: true
 
+# ------------------------------------------------------------------------------------------
+# when testing `parse` methods:
+#
+# * SmarterCSV.default_options are not loaded when testing `parse` methods by themselves
+#
+# * make sure to always pass all options to the 'parse' methods, incl. acceleration
+#
+# * always wrap tests, so that both accelerated and un-accelerated code-paths are run,
+#   because the purpose of these tests is to ensure that both accelerated and unaccelerated
+#   code paths are behaving identically.
+# ------------------------------------------------------------------------------------------
+
 require 'spec_helper'
 
 # the purpose of the max_size parameter is to handle a corner case where
diff --git a/spec/smarter_csv/parse/old_csv_library_spec.rb b/spec/smarter_csv/parse/old_csv_library_spec.rb
index 16a45cfe..9231f7d4 100644
--- a/spec/smarter_csv/parse/old_csv_library_spec.rb
+++ b/spec/smarter_csv/parse/old_csv_library_spec.rb
@@ -1,5 +1,17 @@
 # frozen_string_literal: true
 
+# ------------------------------------------------------------------------------------------
+# when testing `parse` methods:
+#
+# * SmarterCSV.default_options are not loaded when testing `parse` methods by themselves
+#
+# * make sure to always pass all options to the 'parse' methods, incl. acceleration
+#
+# * always wrap tests, so that both accelerated and un-accelerated code-paths are run,
+#   because the purpose of these tests is to ensure that both accelerated and unaccelerated
+#   code paths are behaving identically.
+# ------------------------------------------------------------------------------------------
+
 require 'spec_helper'
 
 [true, false].each do |bool|
diff --git a/spec/smarter_csv/parse/rfc4180_and_more_spec.rb b/spec/smarter_csv/parse/rfc4180_and_more_spec.rb
index b6a4fe48..e315cf2a 100644
--- a/spec/smarter_csv/parse/rfc4180_and_more_spec.rb
+++ b/spec/smarter_csv/parse/rfc4180_and_more_spec.rb
@@ -1,5 +1,17 @@
 # frozen_string_literal: true
 
+# ------------------------------------------------------------------------------------------
+# when testing `parse` methods:
+#
+# * SmarterCSV.default_options are not loaded when testing `parse` methods by themselves
+#
+# * make sure to always pass all options to the 'parse' methods, incl. acceleration
+#
+# * always wrap tests, so that both accelerated and un-accelerated code-paths are run,
+#   because the purpose of these tests is to ensure that both accelerated and unaccelerated
+#   code paths are behaving identically.
+# ------------------------------------------------------------------------------------------
+
 require 'spec_helper'
 
 [true, false].each do |bool|