1 files changed, 20 insertions, 5 deletions
diff --git a/spec/ruby/library/stringio/putc_spec.rb b/spec/ruby/library/stringio/putc_spec.rb
index 223b3523e5..9f1ac8ffb2 100644
--- a/spec/ruby/library/stringio/putc_spec.rb
+++ b/spec/ruby/library/stringio/putc_spec.rb
@@ -3,7 +3,7 @@ require_relative 'fixtures/classes'
 
 describe "StringIO#putc when passed [String]" do
   before :each do
-    @io = StringIO.new('example')
+    @io = StringIO.new(+'example')
   end
 
   it "overwrites the character at the current position" do
@@ -35,11 +35,26 @@ describe "StringIO#putc when passed [String]" do
     @io.putc("t")
     @io.pos.should == 3
   end
+
+  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.putc i.to_s
+      }
+    }
+    go = true
+    threads.each(&:join)
+    @io.string.size.should == n
+  end
 end
 
 describe "StringIO#putc when passed [Object]" do
   before :each do
-    @io = StringIO.new('example')
+    @io = StringIO.new(+'example')
   end
 
   it "it writes the passed Integer % 256 to self" do
@@ -70,7 +85,7 @@ end
 
 describe "StringIO#putc when in append mode" do
   it "appends to the end of self" do
-    io = StringIO.new("test", "a")
+    io = StringIO.new(+"test", "a")
     io.putc(?t)
     io.string.should == "testt"
   end
@@ -78,10 +93,10 @@ end
 
 describe "StringIO#putc when self is not writable" do
   it "raises an IOError" do
-    io = StringIO.new("test", "r")
+    io = StringIO.new(+"test", "r")
     -> { io.putc(?a) }.should raise_error(IOError)
 
-    io = StringIO.new("test")
+    io = StringIO.new(+"test")
     io.close_write
     -> { io.putc("t") }.should raise_error(IOError)
   end