1 files changed, 16 insertions, 6 deletions
diff --git a/spec/ruby/core/array/pack/buffer_spec.rb b/spec/ruby/core/array/pack/buffer_spec.rb
index ecb40bfd06..b77b2d1efa 100644
--- a/spec/ruby/core/array/pack/buffer_spec.rb
+++ b/spec/ruby/core/array/pack/buffer_spec.rb
@@ -13,13 +13,13 @@ describe "Array#pack with :buffer option" do
   it "adds result at the end of buffer content" do
     n = [ 65, 66, 67 ] # result without buffer is "ABC"
 
-    buffer = ""
+    buffer = +""
     n.pack("ccc", buffer: buffer).should == "ABC"
 
-    buffer = "123"
+    buffer = +"123"
     n.pack("ccc", buffer: buffer).should == "123ABC"
 
-    buffer = "12345"
+    buffer = +"12345"
     n.pack("ccc", buffer: buffer).should == "12345ABC"
   end
 
@@ -28,22 +28,32 @@ describe "Array#pack with :buffer option" do
       TypeError, "buffer must be String, not Array")
   end
 
+  it "raise FrozenError if buffer is frozen" do
+    -> { [65].pack("c", buffer: "frozen-string".freeze) }.should raise_error(FrozenError)
+  end
+
+  it "preserves the encoding of the given buffer" do
+    buffer = ''.encode(Encoding::ISO_8859_1)
+    [65, 66, 67].pack("ccc", buffer: buffer)
+    buffer.encoding.should == Encoding::ISO_8859_1
+  end
+
   context "offset (@) is specified" do
     it 'keeps buffer content if it is longer than offset' do
       n = [ 65, 66, 67 ]
-      buffer = "123456"
+      buffer = +"123456"
       n.pack("@3ccc", buffer: buffer).should == "123ABC"
     end
 
     it "fills the gap with \\0 if buffer content is shorter than offset" do
       n = [ 65, 66, 67 ]
-      buffer = "123"
+      buffer = +"123"
       n.pack("@6ccc", buffer: buffer).should == "123\0\0\0ABC"
     end
 
     it 'does not keep buffer content if it is longer than offset + result' do
       n = [ 65, 66, 67 ]
-      buffer = "1234567890"
+      buffer = +"1234567890"
       n.pack("@3ccc", buffer: buffer).should == "123ABC"
     end
   end