[ruby/yarp] Set default external encoding for parse tests

https://github.com/ruby/yarp/commit/e757fde3ed

test/yarp/parse_test.rb

@@ -3,6 +3,19 @@
 require "yarp_test_helper"
 
 class ParseTest < Test::Unit::TestCase
+  # Because we're reading the snapshots from disk, we need to make sure that
+  # they're encoded as UTF-8. When certain settings are present this might not
+  # always be the case (e.g., LANG=C or -Eascii-8bit). So here we force the
+  # default external encoding for the duration of the test.
+  def setup
+    @previous_default_external = Encoding.default_external
+    Encoding.default_external = Encoding::UTF_8
+  end
+
+  def teardown
+    Encoding.default_external = @previous_default_external
+  end
+
   def test_Ruby_3_2_plus
     assert_operator RUBY_VERSION, :>=, "3.2.0", "ParseTest requires Ruby 3.2+"
   end
@@ -48,24 +61,6 @@ class ParseTest < Test::Unit::TestCase
     assert_equal filepath, find_source_file_node(parsed_result.value).filepath
   end
 
-  # We have some files that are failing on other systems because of default
-  # encoding. We'll fix these ASAP.
-  FAILING = %w[
-    seattlerb/bug202.txt
-    seattlerb/dsym_esc_to_sym.txt
-    seattlerb/heredoc_bad_oct_escape.txt
-    seattlerb/magic_encoding_comment.txt
-    seattlerb/read_escape_unicode_curlies.txt
-    seattlerb/read_escape_unicode_h4.txt
-    seattlerb/regexp_escape_extended.txt
-    seattlerb/regexp_unicode_curlies.txt
-    seattlerb/str_evstr_escape.txt
-    seattlerb/str_lit_concat_bad_encodings.txt
-    symbols.txt
-    whitequark/bug_ascii_8bit_in_literal.txt
-    whitequark/dedenting_heredoc.txt
-  ]
-
   Dir[File.expand_path("fixtures/**/*.txt", __dir__)].each do |filepath|
     relative = filepath.delete_prefix("#{File.expand_path("fixtures", __dir__)}/")
     next if known_failures.include?(relative)
@@ -75,12 +70,6 @@ class ParseTest < Test::Unit::TestCase
     FileUtils.mkdir_p(directory) unless File.directory?(directory)
 
     define_method "test_filepath_#{filepath}" do
-      if (ENV.key?("RUBYCI_NICKNAME") || ENV["RUBY_DEBUG"] =~ /ci/) && FAILING.include?(relative)
-        # http://rubyci.s3.amazonaws.com/solaris10-gcc/ruby-master/log/20230621T190004Z.fail.html.gz
-        # http://ci.rvm.jp/results/trunk-yjit@ruby-sp2-docker/4612202
-        omit "Not working on RubyCI and ci.rvm.jp"
-      end
-
       # First, read the source from the filepath. Use binmode to avoid converting CRLF on Windows,
       # and explicitly set the external encoding to UTF-8 to override the binmode default.
       source = File.read(filepath, binmode: true, external_encoding: Encoding::UTF_8)