1 files changed, 47 insertions, 1 deletions
diff --git a/test/stringio/test_stringio.rb b/test/stringio/test_stringio.rb
index 570b3d7ad6..024906261e 100644
--- a/test/stringio/test_stringio.rb
+++ b/test/stringio/test_stringio.rb
@@ -70,6 +70,31 @@ class TestStringIO < Test::Unit::TestCase
     assert_nil io.getc
   end
 
+  def test_eof_null
+    io = StringIO.new(nil)
+    assert_predicate io, :eof?
+  end
+
+  def test_pread_null
+    io = StringIO.new(nil)
+    assert_raise(EOFError) { io.pread(1, 0) }
+  end
+
+  def test_read_null
+    io = StringIO.new(nil)
+    assert_equal "", io.read(0)
+  end
+
+  def test_seek_null
+    io = StringIO.new(nil)
+    assert_equal(0, io.seek(0, IO::SEEK_SET))
+    assert_equal(0, io.pos)
+    assert_equal(0, io.seek(0, IO::SEEK_CUR))
+    assert_equal(0, io.pos)
+    assert_equal(0, io.seek(0, IO::SEEK_END))  # This should not segfault
+    assert_equal(0, io.pos)
+  end
+
   def test_truncate
     io = StringIO.new("")
     io.puts "abc"
@@ -971,7 +996,7 @@ class TestStringIO < Test::Unit::TestCase
     intptr_max = RbConfig::LIMITS["INTPTR_MAX"]
     return if intptr_max > StringIO::MAX_LENGTH
     limit = intptr_max - 0x10
-    assert_separately(%w[-rstringio], "#{<<-"begin;"}\n#{<<-"end;"}")
+    assert_separately(%w[-W0 -rstringio], "#{<<-"begin;"}\n#{<<-"end;"}")
     begin;
       limit = #{limit}
       ary = []
@@ -1039,6 +1064,20 @@ class TestStringIO < Test::Unit::TestCase
     assert_predicate(s.string, :ascii_only?)
   end
 
+  def test_coderange_after_read_into_buffer
+    s = StringIO.new("01234567890".b)
+
+    buf = "¿Cómo estás? Ça va bien?"
+    assert_not_predicate(buf, :ascii_only?)
+
+    assert_predicate(s.string, :ascii_only?)
+
+    s.read(10, buf)
+
+    assert_predicate(buf, :ascii_only?)
+    assert_equal '0123456789', buf
+  end
+
   require "objspace"
   if ObjectSpace.respond_to?(:dump) && ObjectSpace.dump(eval(%{"test"})).include?('"chilled":true') # Ruby 3.4+ chilled strings
     def test_chilled_string
@@ -1057,6 +1096,13 @@ class TestStringIO < Test::Unit::TestCase
       assert_equal("test", io.string)
       assert_same(chilled_string, io.string)
     end
+
+    def test_chilled_string_set_enocoding
+      chilled_string = eval(%{""})
+      io = StringIO.new(chilled_string)
+      assert_warning("") { io.set_encoding(Encoding::BINARY) }
+      assert_same(chilled_string, io.string)
+    end
   end
 
   private