12 files changed, 501 insertions, 85 deletions

diff --git a/spec/ruby/library/stringio/shared/codepoints.rb b/spec/ruby/library/stringio/shared/codepoints.rb
index c8ca03329f..e35a02ccb4 100644
--- a/spec/ruby/library/stringio/shared/codepoints.rb
+++ b/spec/ruby/library/stringio/shared/codepoints.rb
@@ -6,7 +6,7 @@ describe :stringio_codepoints, shared: true do
   end
 
   it "returns an Enumerator" do
-    @enum.should be_an_instance_of(Enumerator)
+    @enum.should.instance_of?(Enumerator)
   end
 
   it "yields each codepoint code in turn" do
@@ -20,15 +20,15 @@ describe :stringio_codepoints, shared: true do
 
   it "raises an error if reading invalid sequence" do
     @io.pos = 1  # inside of a multibyte sequence
-    lambda { @enum.first }.should raise_error(ArgumentError)
+    -> { @enum.first }.should.raise(ArgumentError)
   end
 
   it "raises an IOError if not readable" do
     @io.close_read
-    lambda { @enum.to_a }.should raise_error(IOError)
+    -> { @enum.to_a }.should.raise(IOError)
 
-    io = StringIO.new("xyz", "w")
-    lambda { io.send(@method).to_a }.should raise_error(IOError)
+    io = StringIO.new(+"xyz", "w")
+    -> { io.send(@method).to_a }.should.raise(IOError)
   end
 
 
@@ -39,7 +39,7 @@ describe :stringio_codepoints, shared: true do
   end
 
   it "returns self" do
-    @io.send(@method) {|l| l }.should equal(@io)
+    @io.send(@method) {|l| l }.should.equal?(@io)
   end
 
 end
diff --git a/spec/ruby/library/stringio/shared/each.rb b/spec/ruby/library/stringio/shared/each.rb
index 55ed27c1c7..04e40b6b2a 100644
--- a/spec/ruby/library/stringio/shared/each.rb
+++ b/spec/ruby/library/stringio/shared/each.rb
@@ -16,7 +16,7 @@ describe :stringio_each_separator, shared: true do
   end
 
   it "returns self" do
-    @io.send(@method) {|l| l }.should equal(@io)
+    @io.send(@method) {|l| l }.should.equal?(@io)
   end
 
   it "tries to convert the passed separator to a String using #to_str" do
@@ -36,11 +36,11 @@ describe :stringio_each_separator, shared: true do
     seen.should == ["2 1 2 1 2"]
   end
 
-  it "yields each paragraph when passed an empty String as separator" do
+  it "yields each paragraph with all separation characters when passed an empty String as separator" do
     seen = []
     io = StringIO.new("para1\n\npara2\n\n\npara3")
     io.send(@method, "") {|s| seen << s}
-    seen.should == ["para1\n\n", "para2\n\n", "para3"]
+    seen.should == ["para1\n\n", "para2\n\n\n", "para3"]
   end
 end
 
@@ -71,21 +71,22 @@ describe :stringio_each_no_arguments, shared: true do
   it "uses $/ as the default line separator" do
     seen = []
     begin
-      old_rs, $/ = $/, " "
+      old_rs = $/
+      suppress_warning {$/ = " "}
       @io.send(@method) {|s| seen << s }
-      seen.should eql(["a ", "b ", "c ", "d ", "e\n1 ", "2 ", "3 ", "4 ", "5"])
+      seen.should.eql?(["a ", "b ", "c ", "d ", "e\n1 ", "2 ", "3 ", "4 ", "5"])
     ensure
-      $/ = old_rs
+      suppress_warning {$/ = old_rs}
     end
   end
 
   it "returns self" do
-    @io.send(@method) {|l| l }.should equal(@io)
+    @io.send(@method) {|l| l }.should.equal?(@io)
   end
 
   it "returns an Enumerator when passed no block" do
     enum = @io.send(@method)
-    enum.instance_of?(Enumerator).should be_true
+    enum.instance_of?(Enumerator).should == true
 
     seen = []
     enum.each { |b| seen << b }
@@ -95,12 +96,12 @@ end
 
 describe :stringio_each_not_readable, shared: true do
   it "raises an IOError" do
-    io = StringIO.new("a b c d e", "w")
-    lambda { io.send(@method) { |b| b } }.should raise_error(IOError)
+    io = StringIO.new(+"a b c d e", "w")
+    -> { io.send(@method) { |b| b } }.should.raise(IOError)
 
     io = StringIO.new("a b c d e")
     io.close_read
-    lambda { io.send(@method) { |b| b } }.should raise_error(IOError)
+    -> { io.send(@method) { |b| b } }.should.raise(IOError)
   end
 end
 
@@ -111,4 +112,98 @@ describe :stringio_each_chomp, shared: true do
     io.send(@method, chomp: true) {|s| seen << s }
     seen.should == ["a b \rc d e", "1 2 3 4 5", "the end"]
   end
+
+  it "returns each line with removed newline characters when called without block" do
+    seen = []
+    io = StringIO.new("a b \rc d e\n1 2 3 4 5\r\nthe end")
+    enum = io.send(@method, chomp: true)
+    enum.each {|s| seen << s }
+    seen.should == ["a b \rc d e", "1 2 3 4 5", "the end"]
+  end
+end
+
+describe :stringio_each_separator_and_chomp, shared: true do
+  it "yields each line with removed separator to the passed block" do
+    seen = []
+    io = StringIO.new("a b \nc d e|1 2 3 4 5\n|the end")
+    io.send(@method, "|", chomp: true) {|s| seen << s }
+    seen.should == ["a b \nc d e", "1 2 3 4 5\n", "the end"]
+  end
+
+  it "returns each line with removed separator when called without block" do
+    seen = []
+    io = StringIO.new("a b \nc d e|1 2 3 4 5\n|the end")
+    enum = io.send(@method, "|", chomp: true)
+    enum.each {|s| seen << s }
+    seen.should == ["a b \nc d e", "1 2 3 4 5\n", "the end"]
+  end
+end
+
+describe :stringio_each_limit, shared: true do
+  before :each do
+    @io = StringIO.new("a b c d e\n1 2 3 4 5")
+  end
+
+  it "returns the data read until the limit is met" do
+    seen = []
+    @io.send(@method, 4) { |s| seen << s }
+    seen.should == ["a b ", "c d ", "e\n", "1 2 ", "3 4 ", "5"]
+  end
+end
+
+describe :stringio_each_separator_and_limit, shared: true do
+  before :each do
+    @io = StringIO.new("this>is>an>example")
+  end
+
+  it "returns the data read until the limit is consumed or the separator is met" do
+    @io.send(@method, '>', 8) { |s| break s }.should == "this>"
+    @io.send(@method, '>', 2) { |s| break s }.should == "is"
+    @io.send(@method, '>', 10) { |s| break s }.should == ">"
+    @io.send(@method, '>', 6) { |s| break s }.should == "an>"
+    @io.send(@method, '>', 5) { |s| break s }.should == "examp"
+  end
+
+  it "truncates the multi-character separator at the end to meet the limit" do
+    @io.send(@method, "is>an", 7) { |s| break s }.should == "this>is"
+  end
+
+  it "does not change $_" do
+    $_ = "test"
+    @io.send(@method, '>', 8) { |s| s }
+    $_.should == "test"
+  end
+
+  it "updates self's lineno by one" do
+    @io.send(@method, '>', 3) { |s| break s }
+    @io.lineno.should.eql?(1)
+
+    @io.send(@method, '>', 3) { |s| break s }
+    @io.lineno.should.eql?(2)
+
+    @io.send(@method, '>', 3) { |s| break s }
+    @io.lineno.should.eql?(3)
+  end
+
+  it "tries to convert the passed separator to a String using #to_str" do # TODO
+    obj = mock('to_str')
+    obj.should_receive(:to_str).and_return('>')
+
+    seen = []
+    @io.send(@method, obj, 5) { |s| seen << s }
+    seen.should == ["this>", "is>", "an>", "examp", "le"]
+  end
+
+  it "does not raise TypeError if passed separator is nil" do
+    @io.send(@method, nil, 5) { |s| break s }.should == "this>"
+  end
+
+  it "tries to convert the passed limit to an Integer using #to_int" do # TODO
+    obj = mock('to_int')
+    obj.should_receive(:to_int).and_return(5)
+
+    seen = []
+    @io.send(@method, '>', obj) { |s| seen << s }
+    seen.should == ["this>", "is>", "an>", "examp", "le"]
+  end
 end
diff --git a/spec/ruby/library/stringio/shared/each_byte.rb b/spec/ruby/library/stringio/shared/each_byte.rb
index 1dc48ee437..b3939c26de 100644
--- a/spec/ruby/library/stringio/shared/each_byte.rb
+++ b/spec/ruby/library/stringio/shared/each_byte.rb
@@ -19,16 +19,16 @@ describe :stringio_each_byte, shared: true do
     @io.pos = 1000
     seen = nil
     @io.send(@method) { |b| seen = b }
-    seen.should be_nil
+    seen.should == nil
   end
 
   it "returns self" do
-    @io.send(@method) {}.should equal(@io)
+    @io.send(@method) {}.should.equal?(@io)
   end
 
   it "returns an Enumerator when passed no block" do
     enum = @io.send(@method)
-    enum.instance_of?(Enumerator).should be_true
+    enum.instance_of?(Enumerator).should == true
 
     seen = []
     enum.each { |b| seen << b }
@@ -38,11 +38,11 @@ end
 
 describe :stringio_each_byte_not_readable, shared: true do
   it "raises an IOError" do
-    io = StringIO.new("xyz", "w")
-    lambda { io.send(@method) { |b| b } }.should raise_error(IOError)
+    io = StringIO.new(+"xyz", "w")
+    -> { io.send(@method) { |b| b } }.should.raise(IOError)
 
     io = StringIO.new("xyz")
     io.close_read
-    lambda { io.send(@method) { |b| b } }.should raise_error(IOError)
+    -> { io.send(@method) { |b| b } }.should.raise(IOError)
   end
 end
diff --git a/spec/ruby/library/stringio/shared/each_char.rb b/spec/ruby/library/stringio/shared/each_char.rb
index 35efdcb749..4215a9952b 100644
--- a/spec/ruby/library/stringio/shared/each_char.rb
+++ b/spec/ruby/library/stringio/shared/each_char.rb
@@ -11,12 +11,12 @@ describe :stringio_each_char, shared: true do
   end
 
   it "returns self" do
-    @io.send(@method) {}.should equal(@io)
+    @io.send(@method) {}.should.equal?(@io)
   end
 
   it "returns an Enumerator when passed no block" do
     enum = @io.send(@method)
-    enum.instance_of?(Enumerator).should be_true
+    enum.instance_of?(Enumerator).should == true
 
     seen = []
     enum.each { |c| seen << c }
@@ -26,11 +26,11 @@ end
 
 describe :stringio_each_char_not_readable, shared: true do
   it "raises an IOError" do
-    io = StringIO.new("xyz", "w")
-    lambda { io.send(@method) { |b| b } }.should raise_error(IOError)
+    io = StringIO.new(+"xyz", "w")
+    -> { io.send(@method) { |b| b } }.should.raise(IOError)
 
     io = StringIO.new("xyz")
     io.close_read
-    lambda { io.send(@method) { |b| b } }.should raise_error(IOError)
+    -> { io.send(@method) { |b| b } }.should.raise(IOError)
   end
 end
diff --git a/spec/ruby/library/stringio/shared/eof.rb b/spec/ruby/library/stringio/shared/eof.rb
index e0368a2892..a9489581fc 100644
--- a/spec/ruby/library/stringio/shared/eof.rb
+++ b/spec/ruby/library/stringio/shared/eof.rb
@@ -5,20 +5,20 @@ describe :stringio_eof, shared: true do
 
   it "returns true when self's position is greater than or equal to self's size" do
     @io.pos = 3
-    @io.send(@method).should be_true
+    @io.send(@method).should == true
 
     @io.pos = 6
-    @io.send(@method).should be_true
+    @io.send(@method).should == true
   end
 
   it "returns false when self's position is less than self's size" do
     @io.pos = 0
-    @io.send(@method).should be_false
+    @io.send(@method).should == false
 
     @io.pos = 1
-    @io.send(@method).should be_false
+    @io.send(@method).should == false
 
     @io.pos = 2
-    @io.send(@method).should be_false
+    @io.send(@method).should == false
   end
 end
diff --git a/spec/ruby/library/stringio/shared/getc.rb b/spec/ruby/library/stringio/shared/getc.rb
index 3e064f9c1e..a146b2d4cf 100644
--- a/spec/ruby/library/stringio/shared/getc.rb
+++ b/spec/ruby/library/stringio/shared/getc.rb
@@ -5,39 +5,39 @@ describe :stringio_getc, shared: true do
 
   it "increases self's position by one" do
     @io.send(@method)
-    @io.pos.should eql(1)
+    @io.pos.should.eql?(1)
 
     @io.send(@method)
-    @io.pos.should eql(2)
+    @io.pos.should.eql?(2)
 
     @io.send(@method)
-    @io.pos.should eql(3)
+    @io.pos.should.eql?(3)
   end
 
   it "returns nil when called at the end of self" do
     @io.pos = 7
-    @io.send(@method).should be_nil
-    @io.send(@method).should be_nil
-    @io.send(@method).should be_nil
+    @io.send(@method).should == nil
+    @io.send(@method).should == nil
+    @io.send(@method).should == nil
   end
 
   it "does not increase self's position when called at the end of file" do
     @io.pos = 7
     @io.send(@method)
-    @io.pos.should eql(7)
+    @io.pos.should.eql?(7)
 
     @io.send(@method)
-    @io.pos.should eql(7)
+    @io.pos.should.eql?(7)
   end
 end
 
 describe :stringio_getc_not_readable, shared: true do
   it "raises an IOError" do
-    io = StringIO.new("xyz", "w")
-    lambda { io.send(@method) }.should raise_error(IOError)
+    io = StringIO.new(+"xyz", "w")
+    -> { io.send(@method) }.should.raise(IOError)
 
     io = StringIO.new("xyz")
     io.close_read
-    lambda { io.send(@method) }.should raise_error(IOError)
+    -> { io.send(@method) }.should.raise(IOError)
   end
 end
diff --git a/spec/ruby/library/stringio/shared/gets.rb b/spec/ruby/library/stringio/shared/gets.rb
new file mode 100644
index 0000000000..16039b18ef
--- /dev/null
+++ b/spec/ruby/library/stringio/shared/gets.rb
@@ -0,0 +1,249 @@
+describe :stringio_gets_separator, shared: true do
+  describe "when passed [separator]" do
+    before :each do
+      @io = StringIO.new("this>is>an>example")
+    end
+
+    it "returns the data read till the next occurrence of the passed separator" do
+      @io.send(@method, ">").should == "this>"
+      @io.send(@method, ">").should == "is>"
+      @io.send(@method, ">").should == "an>"
+      @io.send(@method, ">").should == "example"
+    end
+
+    it "sets $_ to the read content" do
+      @io.send(@method, ">")
+      $_.should == "this>"
+      @io.send(@method, ">")
+      $_.should == "is>"
+      @io.send(@method, ">")
+      $_.should == "an>"
+      @io.send(@method, ">")
+      $_.should == "example"
+    end
+
+    it "accepts string as separator" do
+      @io.send(@method, "is>")
+      $_.should == "this>"
+      @io.send(@method, "an>")
+      $_.should == "is>an>"
+      @io.send(@method, "example")
+      $_.should == "example"
+    end
+
+    it "updates self's lineno by one" do
+      @io.send(@method, ">")
+      @io.lineno.should.eql?(1)
+
+      @io.send(@method, ">")
+      @io.lineno.should.eql?(2)
+
+      @io.send(@method, ">")
+      @io.lineno.should.eql?(3)
+    end
+
+    it "returns the next paragraph when the passed separator is an empty String" do
+      io = StringIO.new("this is\n\nan example")
+      io.send(@method, "").should == "this is\n\n"
+      io.send(@method, "").should == "an example"
+    end
+
+    it "returns the remaining content starting at the current position when passed nil" do
+      io = StringIO.new("this is\n\nan example")
+      io.pos = 5
+      io.send(@method, nil).should == "is\n\nan example"
+    end
+
+    it "tries to convert the passed separator to a String using #to_str" do
+      obj = mock('to_str')
+      obj.should_receive(:to_str).and_return(">")
+      @io.send(@method, obj).should == "this>"
+    end
+  end
+end
+
+describe :stringio_gets_limit, shared: true do
+  describe "when passed [limit]" do
+    before :each do
+      @io = StringIO.new("this>is>an>example")
+    end
+
+    it "returns the data read until the limit is met" do
+      @io.send(@method, 4).should == "this"
+      @io.send(@method, 3).should == ">is"
+      @io.send(@method, 5).should == ">an>e"
+      @io.send(@method, 6).should == "xample"
+    end
+
+    it "sets $_ to the read content" do
+      @io.send(@method, 4)
+      $_.should == "this"
+      @io.send(@method, 3)
+      $_.should == ">is"
+      @io.send(@method, 5)
+      $_.should == ">an>e"
+      @io.send(@method, 6)
+      $_.should == "xample"
+    end
+
+    it "updates self's lineno by one" do
+      @io.send(@method, 3)
+      @io.lineno.should.eql?(1)
+
+      @io.send(@method, 3)
+      @io.lineno.should.eql?(2)
+
+      @io.send(@method, 3)
+      @io.lineno.should.eql?(3)
+    end
+
+    it "tries to convert the passed limit to an Integer using #to_int" do
+      obj = mock('to_int')
+      obj.should_receive(:to_int).and_return(4)
+      @io.send(@method, obj).should == "this"
+    end
+
+    it "returns a blank string when passed a limit of 0" do
+      @io.send(@method, 0).should == ""
+    end
+
+    it "ignores it when passed a negative limit" do
+      @io.send(@method, -4).should == "this>is>an>example"
+    end
+  end
+end
+
+describe :stringio_gets_separator_and_limit, shared: true do
+  describe "when passed [separator] and [limit]" do
+    before :each do
+      @io = StringIO.new("this>is>an>example")
+    end
+
+    it "returns the data read until the limit is consumed or the separator is met" do
+      @io.send(@method, '>', 8).should == "this>"
+      @io.send(@method, '>', 2).should == "is"
+      @io.send(@method, '>', 10).should == ">"
+      @io.send(@method, '>', 6).should == "an>"
+      @io.send(@method, '>', 5).should == "examp"
+    end
+
+    it "truncates the multi-character separator at the end to meet the limit" do
+      @io.send(@method, "is>an", 7).should == "this>is"
+    end
+
+    it "sets $_ to the read content" do
+      @io.send(@method, '>', 8)
+      $_.should == "this>"
+      @io.send(@method, '>', 2)
+      $_.should == "is"
+      @io.send(@method, '>', 10)
+      $_.should == ">"
+      @io.send(@method, '>', 6)
+      $_.should == "an>"
+      @io.send(@method, '>', 5)
+      $_.should == "examp"
+    end
+
+    it "updates self's lineno by one" do
+      @io.send(@method, '>', 3)
+      @io.lineno.should.eql?(1)
+
+      @io.send(@method, '>', 3)
+      @io.lineno.should.eql?(2)
+
+      @io.send(@method, '>', 3)
+      @io.lineno.should.eql?(3)
+    end
+
+    it "tries to convert the passed separator to a String using #to_str" do
+      obj = mock('to_str')
+      obj.should_receive(:to_str).and_return('>')
+      @io.send(@method, obj, 5).should == "this>"
+    end
+
+    it "does not raise TypeError if passed separator is nil" do
+      @io.send(@method, nil, 5).should == "this>"
+    end
+
+    it "tries to convert the passed limit to an Integer using #to_int" do
+      obj = mock('to_int')
+      obj.should_receive(:to_int).and_return(5)
+      @io.send(@method, '>', obj).should == "this>"
+    end
+  end
+end
+
+describe :stringio_gets_no_argument, shared: true do
+  describe "when passed no argument" do
+    before :each do
+      @io = StringIO.new("this is\nan example\nfor StringIO#gets")
+    end
+
+    it "returns the data read till the next occurrence of $/ or till eof" do
+      @io.send(@method).should == "this is\n"
+
+      begin
+        old_sep = $/
+        suppress_warning {$/ = " "}
+        @io.send(@method).should == "an "
+        @io.send(@method).should == "example\nfor "
+        @io.send(@method).should == "StringIO#gets"
+      ensure
+        suppress_warning {$/ = old_sep}
+      end
+    end
+
+    it "sets $_ to the read content" do
+      @io.send(@method)
+      $_.should == "this is\n"
+      @io.send(@method)
+      $_.should == "an example\n"
+      @io.send(@method)
+      $_.should == "for StringIO#gets"
+    end
+
+    it "updates self's position" do
+      @io.send(@method)
+      @io.pos.should.eql?(8)
+
+      @io.send(@method)
+      @io.pos.should.eql?(19)
+
+      @io.send(@method)
+      @io.pos.should.eql?(36)
+    end
+
+    it "updates self's lineno" do
+      @io.send(@method)
+      @io.lineno.should.eql?(1)
+
+      @io.send(@method)
+      @io.lineno.should.eql?(2)
+
+      @io.send(@method)
+      @io.lineno.should.eql?(3)
+    end
+  end
+end
+
+describe :stringio_gets_chomp, shared: true do
+  describe "when passed [chomp]" do
+    it "returns the data read without a trailing newline character" do
+      io = StringIO.new("this>is>an>example\n")
+      io.send(@method, chomp: true).should == "this>is>an>example"
+    end
+  end
+end
+
+describe :stringio_gets_write_only, shared: true do
+  describe "when in write-only mode" do
+    it "raises an IOError" do
+      io = StringIO.new(+"xyz", "w")
+      -> { io.send(@method) }.should.raise(IOError)
+
+      io = StringIO.new("xyz")
+      io.close_read
+      -> { io.send(@method) }.should.raise(IOError)
+    end
+  end
+end
diff --git a/spec/ruby/library/stringio/shared/isatty.rb b/spec/ruby/library/stringio/shared/isatty.rb
index 3da5999953..2b92e8d656 100644
--- a/spec/ruby/library/stringio/shared/isatty.rb
+++ b/spec/ruby/library/stringio/shared/isatty.rb
@@ -1,5 +1,5 @@
 describe :stringio_isatty, shared: true do
   it "returns false" do
-    StringIO.new('tty').send(@method).should be_false
+    StringIO.new("tty").send(@method).should == false
   end
 end
diff --git a/spec/ruby/library/stringio/shared/read.rb b/spec/ruby/library/stringio/shared/read.rb
index 604bf880e5..6e04e75dba 100644
--- a/spec/ruby/library/stringio/shared/read.rb
+++ b/spec/ruby/library/stringio/shared/read.rb
@@ -5,30 +5,48 @@ describe :stringio_read, shared: true do
 
   it "returns the passed buffer String" do
     # Note: Rubinius bug:
-    # @io.send(@method, 7, buffer = "").should equal(buffer)
-    ret = @io.send(@method, 7, buffer = "")
-    ret.should equal(buffer)
+    # @io.send(@method, 7, buffer = +"").should.equal?(buffer)
+    ret = @io.send(@method, 7, buffer = +"")
+    ret.should.equal?(buffer)
   end
 
   it "reads length bytes and writes them to the buffer String" do
-    @io.send(@method, 7, buffer = "")
+    @io.send(@method, 7, buffer = +"").should.equal?(buffer)
     buffer.should == "example"
   end
 
+  guard -> { StringIO::VERSION < "3.1.2" } do
+    it "does not preserve the encoding of the given buffer" do
+      buffer = ''.encode(Encoding::ISO_8859_1)
+      @io.send(@method, 7, buffer)
+
+      buffer.encoding.should_not == Encoding::ISO_8859_1
+    end
+  end
+
+  guard -> { StringIO::VERSION >= "3.1.2" } do
+    it "preserves the encoding of the given buffer" do
+      buffer = ''.encode(Encoding::ISO_8859_1)
+      @io.send(@method, 7, buffer)
+
+      buffer.encoding.should == Encoding::ISO_8859_1
+    end
+  end
+
   it "tries to convert the passed buffer Object to a String using #to_str" do
     obj = mock("to_str")
-    obj.should_receive(:to_str).and_return(buffer = "")
+    obj.should_receive(:to_str).and_return(buffer = +"")
 
     @io.send(@method, 7, obj)
     buffer.should == "example"
   end
 
   it "raises a TypeError when the passed buffer Object can't be converted to a String" do
-    lambda { @io.send(@method, 7, Object.new) }.should raise_error(TypeError)
+    -> { @io.send(@method, 7, Object.new) }.should.raise(TypeError)
   end
 
-  it "raises a #{frozen_error_class} error when passed a frozen String as buffer" do
-    lambda { @io.send(@method, 7, "".freeze) }.should raise_error(frozen_error_class)
+  it "raises a FrozenError error when passed a frozen String as buffer" do
+    -> { @io.send(@method, 7, "".freeze) }.should.raise(FrozenError)
   end
 end
 
@@ -48,10 +66,10 @@ describe :stringio_read_length, shared: true do
 
   it "correctly updates the position" do
     @io.send(@method, 3)
-    @io.pos.should eql(3)
+    @io.pos.should.eql?(3)
 
     @io.send(@method, 999)
-    @io.pos.should eql(7)
+    @io.pos.should.eql?(7)
   end
 
   it "tries to convert the passed length to an Integer using #to_int" do
@@ -61,21 +79,21 @@ describe :stringio_read_length, shared: true do
   end
 
   it "raises a TypeError when the passed length can't be converted to an Integer" do
-    lambda { @io.send(@method, Object.new) }.should raise_error(TypeError)
+    -> { @io.send(@method, Object.new) }.should.raise(TypeError)
   end
 
   it "raises a TypeError when the passed length is negative" do
-    lambda { @io.send(@method, -2) }.should raise_error(ArgumentError)
+    -> { @io.send(@method, -2) }.should.raise(ArgumentError)
   end
 
   it "returns a binary String" do
-    @io.send(@method, 4).encoding.should == Encoding::ASCII_8BIT
+    @io.send(@method, 4).encoding.should == Encoding::BINARY
   end
 end
 
 describe :stringio_read_no_arguments, shared: true do
   before :each do
-    @io = StringIO.new("example")
+    @io = StringIO.new(+"example")
   end
 
   it "reads the whole content starting from the current position" do
@@ -87,7 +105,13 @@ describe :stringio_read_no_arguments, shared: true do
 
   it "correctly updates the current position" do
     @io.send(@method)
-    @io.pos.should eql(7)
+    @io.pos.should.eql?(7)
+  end
+
+  it "correctly update the current position in bytes when multi-byte characters are used" do
+    @io.print("example\u03A3") # Overwrite the original string with 8 characters containing 9 bytes.
+    @io.send(@method)
+    @io.pos.should.eql?(9)
   end
 end
 
@@ -105,17 +129,17 @@ describe :stringio_read_nil, shared: true do
 
   it "updates the current position" do
     @io.send(@method, nil)
-    @io.pos.should eql(7)
+    @io.pos.should.eql?(7)
   end
 end
 
 describe :stringio_read_not_readable, shared: true do
   it "raises an IOError" do
-    io = StringIO.new("test", "w")
-    lambda { io.send(@method) }.should raise_error(IOError)
+    io = StringIO.new(+"test", "w")
+    -> { io.send(@method) }.should.raise(IOError)
 
     io = StringIO.new("test")
     io.close_read
-    lambda { io.send(@method) }.should raise_error(IOError)
+    -> { io.send(@method) }.should.raise(IOError)
   end
 end
diff --git a/spec/ruby/library/stringio/shared/readchar.rb b/spec/ruby/library/stringio/shared/readchar.rb
index 19194f0680..5ac28e0743 100644
--- a/spec/ruby/library/stringio/shared/readchar.rb
+++ b/spec/ruby/library/stringio/shared/readchar.rb
@@ -13,17 +13,17 @@ describe :stringio_readchar, shared: true do
 
   it "raises an EOFError when self is at the end" do
     @io.pos = 7
-    lambda { @io.send(@method) }.should raise_error(EOFError)
+    -> { @io.send(@method) }.should.raise(EOFError)
   end
 end
 
 describe :stringio_readchar_not_readable, shared: true do
   it "raises an IOError" do
-    io = StringIO.new("a b c d e", "w")
-    lambda { io.send(@method) }.should raise_error(IOError)
+    io = StringIO.new(+"a b c d e", "w")
+    -> { io.send(@method) }.should.raise(IOError)
 
     io = StringIO.new("a b c d e")
     io.close_read
-    lambda { io.send(@method) }.should raise_error(IOError)
+    -> { io.send(@method) }.should.raise(IOError)
   end
 end
diff --git a/spec/ruby/library/stringio/shared/sysread.rb b/spec/ruby/library/stringio/shared/sysread.rb
index 9800b2339b..bc448d3379 100644
--- a/spec/ruby/library/stringio/shared/sysread.rb
+++ b/spec/ruby/library/stringio/shared/sysread.rb
@@ -1,4 +1,4 @@
-describe :stringio_sysread_length, :shared => true do
+describe :stringio_sysread_length, shared: true do
   before :each do
     @io = StringIO.new("example")
   end
@@ -10,6 +10,6 @@ describe :stringio_sysread_length, :shared => true do
 
   it "raises an EOFError when passed length > 0 and no data remains" do
     @io.read.should == "example"
-    lambda { @io.sysread(1) }.should raise_error(EOFError)
+    -> { @io.send(@method, 1) }.should.raise(EOFError)
   end
 end
diff --git a/spec/ruby/library/stringio/shared/write.rb b/spec/ruby/library/stringio/shared/write.rb
index bcb548bbd0..b6bffe7f12 100644
--- a/spec/ruby/library/stringio/shared/write.rb
+++ b/spec/ruby/library/stringio/shared/write.rb
@@ -1,6 +1,6 @@
 describe :stringio_write, shared: true do
   before :each do
-    @io = StringIO.new('12345')
+    @io = StringIO.new(+'12345')
   end
 
   it "tries to convert the passed Object to a String using #to_s" do
@@ -13,7 +13,7 @@ end
 
 describe :stringio_write_string, shared: true do
   before :each do
-    @io = StringIO.new('12345')
+    @io = StringIO.new(+'12345')
   end
 
   # TODO: RDoc says that #write appends at the current position.
@@ -42,34 +42,82 @@ describe :stringio_write_string, shared: true do
 
   it "updates self's position" do
     @io.send(@method, 'test')
-    @io.pos.should eql(4)
+    @io.pos.should.eql?(4)
   end
 
-  it "taints self's String when the passed argument is tainted" do
-    @io.send(@method, "test".taint)
-    @io.string.tainted?.should be_true
+  it "handles concurrent writes correctly" do
+    @io = StringIO.new
+    n = 8
+    go = false
+    threads = n.times.map { |i|
+      Thread.new {
+        Thread.pass until go
+        @io.write i.to_s
+      }
+    }
+    go = true
+    threads.each(&:join)
+    @io.string.size.should == n.times.map(&:to_s).join.size
   end
 
-  it "does not taint self when the passed argument is tainted" do
-    @io.send(@method, "test".taint)
-    @io.tainted?.should be_false
+  it "handles writing non-ASCII UTF-8 after seek" do
+    @io.binmode
+    @io << "\x80"
+    @io.pos = 0
+    @io << "\x81"
+    @io.string.should == "\x812345".b
+  end
+
+  it "handles writing with position < buffer size" do
+    @io.pos = 2
+    @io.write "abc"
+    @io.string.should == "12abc"
+
+    @io.pos = 2
+    @io.write "de"
+    @io.string.should == "12dec"
+
+    @io.pos = 2
+    @io.write "fghi"
+    @io.string.should == "12fghi"
+  end
+
+  it "transcodes the given string when the external encoding is set and neither is BINARY" do
+    utf8_str = "hello"
+    io = StringIO.new.set_encoding(Encoding::UTF_16BE)
+    io.external_encoding.should == Encoding::UTF_16BE
+
+    io.send(@method, utf8_str)
+
+    expected = [0, 104, 0, 101, 0, 108, 0, 108, 0, 111] # UTF-16BE bytes for "hello"
+    io.string.bytes.should == expected
+  end
+
+  it "does not transcode the given string when the external encoding is set and the string encoding is BINARY" do
+    str = "été_".b
+    io = StringIO.new.set_encoding(Encoding::UTF_16BE)
+    io.external_encoding.should == Encoding::UTF_16BE
+
+    io.send(@method, str)
+
+    io.string.bytes.should == str.bytes
   end
 end
 
 describe :stringio_write_not_writable, shared: true do
   it "raises an IOError" do
-    io = StringIO.new("test", "r")
-    lambda { io.send(@method, "test") }.should raise_error(IOError)
+    io = StringIO.new(+"test", "r")
+    -> { io.send(@method, "test") }.should.raise(IOError)
 
-    io = StringIO.new("test")
+    io = StringIO.new(+"test")
     io.close_write
-    lambda { io.send(@method, "test") }.should raise_error(IOError)
+    -> { io.send(@method, "test") }.should.raise(IOError)
   end
 end
 
 describe :stringio_write_append, shared: true do
   before :each do
-    @io = StringIO.new("example", "a")
+    @io = StringIO.new(+"example", "a")
   end
 
   it "appends the passed argument to the end of self" do
@@ -82,6 +130,6 @@ describe :stringio_write_append, shared: true do
 
   it "correctly updates self's position" do
     @io.send(@method, ", testing")
-    @io.pos.should eql(16)
+    @io.pos.should.eql?(16)
   end
 end