diff --git a/lib/csv.rb b/lib/csv.rb
index ebb6d67968..dca2a45b6a 100644
--- a/lib/csv.rb
+++ b/lib/csv.rb
@@ -141,7 +141,7 @@ end
 # There are several specialized class methods for one-statement reading or writing,
 # described in the Specialized Methods section.
 #
-# If a String passed into ::new, it is internally wrapped into a StringIO object.
+# If a String is passed into ::new, it is internally wrapped into a StringIO object.
 #
 # +options+ can be used for specifying the particular CSV flavor (column
 # separators, row separators, value quoting and so on), and for data conversion,
@@ -890,8 +890,12 @@ class CSV
   #                                       attempt to parse input not conformant
   #                                       with RFC 4180, such as double quotes
   #                                       in unquoted fields.
-  # <b><tt>:nil_value</tt></b>::          TODO: WRITE ME.
-  # <b><tt>:empty_value</tt></b>::        TODO: WRITE ME.
+  # <b><tt>:nil_value</tt></b>::          When set an object, any values of an
+  #                                       empty field are replaced by the set
+  #                                       object, not nil.
+  # <b><tt>:empty_value</tt></b>::        When set an object, any values of a
+  #                                       blank string field is replaced by
+  #                                       the set object.
   #
   # See CSV::DEFAULT_OPTIONS for the default settings.
   #
@@ -1232,7 +1236,7 @@ class CSV
           elsif @unconverted_fields
             return add_unconverted_fields(Array.new, Array.new)
           elsif @use_headers
-            return self.class::Row.new(Array.new, Array.new)
+            return self.class::Row.new(@headers, Array.new)
           else
             return Array.new
           end
diff --git a/lib/csv/csv.gemspec b/lib/csv/csv.gemspec
index 0169c173d6..9d0ccc15af 100644
--- a/lib/csv/csv.gemspec
+++ b/lib/csv/csv.gemspec
@@ -1,6 +1,10 @@
 # frozen_string_literal: true
 
-require_relative "version"
+begin
+  require_relative "lib/csv/version"
+rescue LoadError
+  require_relative "version"
+end
 
 Gem::Specification.new do |spec|
   spec.name          = "csv"
@@ -13,7 +17,8 @@ Gem::Specification.new do |spec|
   spec.homepage      = "https://github.com/ruby/csv"
   spec.license       = "BSD-2-Clause"
 
-  spec.files         = ["lib/csv.rb", "lib/csv/table.rb", "lib/csv/core_ext/string.rb", "lib/csv/core_ext/array.rb", "lib/csv/row.rb", "lib/csv/version.rb", "README.md", "LICENSE.txt", "news.md"]
+  spec.files         = Dir.glob("lib/**/*.rb")
+  spec.files         += ["README.md", "LICENSE.txt", "news.md"]
   spec.require_paths = ["lib"]
   spec.required_ruby_version = ">= 2.3.0"
 
diff --git a/lib/csv/row.rb b/lib/csv/row.rb
index 8ff3480ae8..31eab2d0a4 100644
--- a/lib/csv/row.rb
+++ b/lib/csv/row.rb
@@ -48,6 +48,11 @@ class CSV
     extend Forwardable
     def_delegators :@row, :empty?, :length, :size
 
+    def initialize_copy(other)
+      super
+      @row = @row.dup
+    end
+
     # Returns +true+ if this is a header row.
     def header_row?
       @header_row
diff --git a/lib/csv/table.rb b/lib/csv/table.rb
index 17a7c542e4..e9f3366a4a 100644
--- a/lib/csv/table.rb
+++ b/lib/csv/table.rb
@@ -375,4 +375,4 @@ class CSV
       "#<#{self.class} mode:#{@mode} row_count:#{to_a.size}>".encode("US-ASCII")
     end
   end
-end
+end
\ No newline at end of file
diff --git a/lib/csv/version.rb b/lib/csv/version.rb
index 35adea3a92..d62a093418 100644
--- a/lib/csv/version.rb
+++ b/lib/csv/version.rb
@@ -2,5 +2,5 @@
 
 class CSV
   # The version of the installed library.
-  VERSION = "1.0.2"
+  VERSION = "3.0.1"
 end
diff --git a/test/csv/test_csv_parsing.rb b/test/csv/test_csv_parsing.rb
index ab8e97f4bb..e65bbad92e 100755
--- a/test/csv/test_csv_parsing.rb
+++ b/test/csv/test_csv_parsing.rb
@@ -148,13 +148,13 @@ class TestCSV::Parsing < TestCSV
       CSV.parse_line("1,2\r,3", row_sep: "\n")
     end
 
-    bad_data = <<-END_DATA.gsub(/^ +/, "")
-    line,1,abc
-    line,2,"def\nghi"
+    bad_data = <<-CSV
+line,1,abc
+line,2,"def\nghi"
 
-    line,4,some\rjunk
-    line,5,jkl
-    END_DATA
+line,4,some\rjunk
+line,5,jkl
+    CSV
     lines = bad_data.lines.to_a
     assert_equal(6, lines.size)
     assert_match(/\Aline,4/, lines.find { |l| l =~ /some\rjunk/ })
@@ -172,13 +172,13 @@ class TestCSV::Parsing < TestCSV
 
     assert_raise(CSV::MalformedCSVError) { CSV.parse_line('1,2,"3...') }
 
-    bad_data = <<-END_DATA.gsub(/^ +/, "")
-    line,1,abc
-    line,2,"def\nghi"
+    bad_data = <<-CSV
+line,1,abc
+line,2,"def\nghi"
 
-    line,4,8'10"
-    line,5,jkl
-    END_DATA
+line,4,8'10"
+line,5,jkl
+    CSV
     lines = bad_data.lines.to_a
     assert_equal(6, lines.size)
     assert_match(/\Aline,4/, lines.find { |l| l =~ /8'10"/ })
diff --git a/test/csv/test_data_converters.rb b/test/csv/test_data_converters.rb
index 04970cd461..114049d66f 100755
--- a/test/csv/test_data_converters.rb
+++ b/test/csv/test_data_converters.rb
@@ -260,10 +260,10 @@ class TestCSV::DataConverters < TestCSV
       assert_equal(unconverted, row.unconverted_fields)
     end
 
-    data = <<-END_CSV.gsub(/^\s+/, "")
-    first,second,third
-    1,2,3
-    END_CSV
+    data = <<-CSV
+first,second,third
+1,2,3
+    CSV
     row = nil
     assert_nothing_raised(Exception) do
       row = CSV.parse_line( data,
diff --git a/test/csv/test_features.rb b/test/csv/test_features.rb
index a851c908f0..45d937e037 100755
--- a/test/csv/test_features.rb
+++ b/test/csv/test_features.rb
@@ -37,12 +37,12 @@ class TestCSV::Features < TestCSV
 
   def setup
     super
-    @sample_data = <<-END_DATA.gsub(/^ +/, "")
-    line,1,abc
-    line,2,"def\nghi"
+    @sample_data = <<-CSV
+line,1,abc
+line,2,"def\nghi"
 
-    line,4,jkl
-    END_DATA
+line,4,jkl
+    CSV
     @csv = CSV.new(@sample_data)
   end
 
@@ -225,12 +225,12 @@ class TestCSV::Features < TestCSV
   end
 
   # reported by Kev Jackson
-  def test_failing_to_escape_col_sep_bug_fix
+  def test_failing_to_escape_col_sep
     assert_nothing_raised(Exception) { CSV.new(String.new, col_sep: "|") }
   end
 
   # reported by Chris Roos
-  def test_failing_to_reset_headers_in_rewind_bug_fix
+  def test_failing_to_reset_headers_in_rewind
     csv = CSV.new("forename,surname", headers: true, return_headers: true)
     csv.each {|row| assert_predicate row, :header_row?}
     csv.rewind
@@ -238,16 +238,16 @@ class TestCSV::Features < TestCSV
   end
 
   # reported by Dave Burt
-  def test_leading_empty_fields_with_multibyte_col_sep_bug_fix
-    data = <<-END_DATA.gsub(/^\s+/, "")
-    <=><=>A<=>B<=>C
-    1<=>2<=>3
-    END_DATA
+  def test_leading_empty_fields_with_multibyte_col_sep
+    data = <<-CSV
+<=><=>A<=>B<=>C
+1<=>2<=>3
+    CSV
     parsed = CSV.parse(data, col_sep: "<=>")
     assert_equal([[nil, nil, "A", "B", "C"], ["1", "2", "3"]], parsed)
   end
 
-  def test_gzip_reader_bug_fix
+  def test_gzip_reader
     zipped = nil
     assert_nothing_raised(NoMethodError) do
       zipped = CSV.new(
@@ -261,7 +261,7 @@ class TestCSV::Features < TestCSV
     zipped.close
   end if defined?(Zlib::GzipReader)
 
-  def test_gzip_writer_bug_fix
+  def test_gzip_writer
     Tempfile.create(%w"temp .gz") {|tempfile|
       tempfile.close
       file = tempfile.path
diff --git a/test/csv/test_headers.rb b/test/csv/test_headers.rb
index 94f4359671..3ebb5cfc85 100755
--- a/test/csv/test_headers.rb
+++ b/test/csv/test_headers.rb
@@ -13,11 +13,11 @@ class TestCSV::Headers < TestCSV
 
   def setup
     super
-    @data = <<-END_CSV.gsub(/^\s+/, "")
-    first,second,third
-    A,B,C
-    1,2,3
-    END_CSV
+    @data = <<-CSV
+first,second,third
+A,B,C
+1,2,3
+    CSV
   end
 
   def test_first_row
@@ -183,10 +183,10 @@ class TestCSV::Headers < TestCSV
 
   def test_converters
     # create test data where headers and fields look alike
-    data = <<-END_MATCHING_CSV.gsub(/^\s+/, "")
-    1,2,3
-    1,2,3
-    END_MATCHING_CSV
+    data = <<-CSV
+1,2,3
+1,2,3
+    CSV
 
     # normal converters do not affect headers
     csv = CSV.parse( data, headers:        true,
@@ -256,16 +256,16 @@ class TestCSV::Headers < TestCSV
   end
 
   def test_skip_blanks
-    @data = <<-END_CSV.gsub(/^ +/, "")
+    @data = <<-CSV
 
 
-    A,B,C
+A,B,C
 
-    1,2,3
+1,2,3
 
 
 
-    END_CSV
+    CSV
 
     expected = [%w[1 2 3]]
     CSV.parse(@data, headers: true, skip_blanks: true) do |row|
@@ -292,7 +292,7 @@ class TestCSV::Headers < TestCSV
     assert_equal(%w[first second third], csv.headers)  # after headers are read
   end
 
-  def test_blank_row_bug_fix
+  def test_blank_row
     @data += "\n#{@data}"  # add a blank row
 
     # ensure that everything returned is a Row object
@@ -300,4 +300,19 @@ class TestCSV::Headers < TestCSV
       assert_instance_of(CSV::Row, row)
     end
   end
+
+  def test_nil_row_header
+    @data = <<-CSV
+A
+
+1
+    CSV
+
+    csv = CSV.parse(@data, headers: true)
+
+    # ensure nil row creates Row object with headers
+    row = csv[0]
+    assert_equal([["A"], [nil]],
+                 [row.headers, row.fields])
+  end
 end
diff --git a/test/csv/test_row.rb b/test/csv/test_row.rb
index 23df4d4fe6..67ed65c0db 100755
--- a/test/csv/test_row.rb
+++ b/test/csv/test_row.rb
@@ -419,4 +419,12 @@ class TestCSV::Row < TestCSV
       row.dig("A", 0)
     end
   end
+
+  def test_dup
+    row = CSV::Row.new(["A"], ["foo"])
+    dupped_row = row.dup
+    dupped_row.delete("A")
+    assert_equal(["foo", nil],
+                 [row["A"], dupped_row["A"]])
+  end
 end
diff --git a/test/csv/test_table.rb b/test/csv/test_table.rb
index 34ea2c5c6b..d99b7d2932 100755
--- a/test/csv/test_table.rb
+++ b/test/csv/test_table.rb
@@ -42,6 +42,11 @@ class TestCSV::Table < TestCSV
     assert_equal(:row, rows.mode)
     assert_equal(@table, rows)
 
+    col_or_row = rows.by_col_or_row
+    assert_equal(:row, rows.mode)
+    assert_equal(:col_or_row, col_or_row.mode)
+    assert_equal(@table, col_or_row)
+
     # destructive mode changing calls
     assert_equal(@table, @table.by_row!)
     assert_equal(:row, @table.mode)
@@ -148,13 +153,13 @@ class TestCSV::Table < TestCSV
                   @table.to_a )
 
     # verify resulting table
-    assert_equal(<<-END_RESULT.gsub(/^\s+/, ""), @table.to_csv)
-    A,B,C,Type,Index
-    1,100,3,data,1
-    4,200,6,data,2
-    10,,12,data,3
-    13,,15,data,
-    END_RESULT
+    assert_equal(<<-CSV, @table.to_csv)
+A,B,C,Type,Index
+1,100,3,data,1
+4,200,6,data,2
+10,,12,data,3
+13,,15,data,
+    CSV
 
     # with headers
     @header_table["Type"] = "data"
@@ -286,12 +291,12 @@ class TestCSV::Table < TestCSV
   end
 
   def test_to_csv
-    csv = <<-END_CSV.gsub(/^\s+/, "")
-    A,B,C
-    1,2,3
-    4,5,6
-    7,8,9
-    END_CSV
+    csv = <<-CSV
+A,B,C
+1,2,3
+4,5,6
+7,8,9
+    CSV
 
     # normal conversion
     assert_equal(csv, @table.to_csv)
@@ -330,11 +335,11 @@ class TestCSV::Table < TestCSV
     assert_equal(@rows.map { |row| row["A"] }, @table.delete("A"))
 
     # verify resulting table
-    assert_equal(<<-END_RESULT.gsub(/^\s+/, ""), @table.to_csv)
-    B,C
-    2,3
-    8,9
-    END_RESULT
+    assert_equal(<<-CSV, @table.to_csv)
+B,C
+2,3
+8,9
+    CSV
   end
 
   def test_delete_mixed_multiple
@@ -352,11 +357,11 @@ class TestCSV::Table < TestCSV
                  @table.delete(1, "A"))
 
     # verify resulting table
-    assert_equal(<<-END_RESULT.gsub(/^\s+/, ""), @table.to_csv)
-    B,C
-    2,3
-    8,9
-    END_RESULT
+    assert_equal(<<-CSV, @table.to_csv)
+B,C
+2,3
+8,9
+    CSV
   end
 
   def test_delete_column
@@ -369,12 +374,12 @@ class TestCSV::Table < TestCSV
     assert_equal(@rows.map { |row| row["C"] }, @table.delete("C"))
 
     # verify resulting table
-    assert_equal(<<-END_RESULT.gsub(/^\s+/, ""), @table.to_csv)
-    B
-    2
-    5
-    8
-    END_RESULT
+    assert_equal(<<-CSV, @table.to_csv)
+B
+2
+5
+8
+    CSV
   end
 
   def test_delete_row
@@ -387,11 +392,11 @@ class TestCSV::Table < TestCSV
     assert_raise(TypeError) { @table.delete("C") }
 
     # verify resulting table
-    assert_equal(<<-END_RESULT.gsub(/^\s+/, ""), @table.to_csv)
-    A,B,C
-    1,2,3
-    7,8,9
-    END_RESULT
+    assert_equal(<<-CSV, @table.to_csv)
+A,B,C
+1,2,3
+7,8,9
+    CSV
   end
 
   def test_delete_with_blank_rows
@@ -408,10 +413,10 @@ class TestCSV::Table < TestCSV
     assert_equal(@table, @table.delete_if { |row| (row["B"] % 2).zero? })
 
     # verify resulting table
-    assert_equal(<<-END_RESULT.gsub(/^\s+/, ""), @table.to_csv)
-    A,B,C
-    4,5,6
-    END_RESULT
+    assert_equal(<<-CSV, @table.to_csv)
+A,B,C
+4,5,6
+    CSV
   end
 
   def test_delete_if_row_without_block
@@ -426,10 +431,10 @@ class TestCSV::Table < TestCSV
     assert_equal(@table, enum.each { |row| (row["B"] % 2).zero? })
 
     # verify resulting table
-    assert_equal(<<-END_RESULT.gsub(/^\s+/, ""), @table.to_csv)
-    A,B,C
-    4,5,6
-    END_RESULT
+    assert_equal(<<-CSV, @table.to_csv)
+A,B,C
+4,5,6
+    CSV
   end
 
   def test_delete_if_column
@@ -439,12 +444,12 @@ class TestCSV::Table < TestCSV
     @table.by_col!
 
     assert_equal(@table, @table.delete_if { |h, v| h > "A" })
-    assert_equal(<<-END_RESULT.gsub(/^\s+/, ""), @table.to_csv)
-    A
-    1
-    4
-    7
-    END_RESULT
+    assert_equal(<<-CSV, @table.to_csv)
+A
+1
+4
+7
+    CSV
   end
 
   def test_delete_if_column_without_block
@@ -458,12 +463,12 @@ class TestCSV::Table < TestCSV
     assert_equal(@table.headers.size, enum.size)
 
     assert_equal(@table, enum.each { |h, v| h > "A" })
-    assert_equal(<<-END_RESULT.gsub(/^\s+/, ""), @table.to_csv)
-    A
-    1
-    4
-    7
-    END_RESULT
+    assert_equal(<<-CSV, @table.to_csv)
+A
+1
+4
+7
+    CSV
   end
 
   def test_values_at