Apply maintainer feedback: improve tests and clean up code

Author: jsxs0

lib/csv/parser.rb

@@ -675,8 +675,6 @@ def prepare_quoted
     def prepare_unquoted
       return if @quote_character.nil?
 
-      # Only exclude characters that are actually part of the row separator
-      # instead of hardcoding "\r\n"
       no_unquoted_values = Regexp.escape(@row_separator).encode(@encoding)
       no_unquoted_values << @escaped_first_column_separator
       unless @liberal_parsing

test/csv/parse/test_general.rb

@@ -156,11 +156,13 @@ def test_unquoted_cr_with_custom_row_separator
     assert_equal(expected, CSV.parse(data, row_sep: "|"))
   end
 
-  def test_unquoted_cr_rejected_when_included_in_row_separator
+  def test_unquoted_cr_with_crlf_row_separator
     data = "field1,field\r2,field3\r\nrow2,data,here\r\n"
-    assert_raise(CSV::MalformedCSVError) do
+    error = assert_raise(CSV::MalformedCSVError) do
       CSV.parse(data, row_sep: "\r\n")
     end
+    assert_equal("Unquoted fields do not allow new line <\"\\r\"> in line 1.",
+                 error.message)
   end
 
   def test_quoted_cr_with_custom_row_separator