1 files changed, 65 insertions, 0 deletions
diff --git a/spec/ruby/core/string/dup_spec.rb b/spec/ruby/core/string/dup_spec.rb
new file mode 100644
index 0000000000..e367f7a311
--- /dev/null
+++ b/spec/ruby/core/string/dup_spec.rb
@@ -0,0 +1,65 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "String#dup" do
+  before :each do
+    ScratchPad.clear
+    @obj = StringSpecs::InitializeString.new "string"
+  end
+
+  it "calls #initialize_copy on the new instance" do
+    dup = @obj.dup
+    ScratchPad.recorded.should_not == @obj.object_id
+    ScratchPad.recorded.should == dup.object_id
+  end
+
+  it "copies instance variables" do
+    dup = @obj.dup
+    dup.ivar.should == 1
+  end
+
+  it "does not copy singleton methods" do
+    def @obj.special() :the_one end
+    dup = @obj.dup
+    -> { dup.special }.should.raise(NameError)
+  end
+
+  it "does not copy modules included in the singleton class" do
+    class << @obj
+      include StringSpecs::StringModule
+    end
+
+    dup = @obj.dup
+    -> { dup.repr }.should.raise(NameError)
+  end
+
+  it "does not copy constants defined in the singleton class" do
+    class << @obj
+      CLONE = :clone
+    end
+
+    dup = @obj.dup
+    -> { class << dup; CLONE; end }.should.raise(NameError)
+  end
+
+  it "does not modify the original string when changing dupped string" do
+    orig = "string"[0..100]
+    dup = orig.dup
+    orig[0] = 'x'
+    orig.should == "xtring"
+    dup.should == "string"
+  end
+
+  it "does not modify the original setbyte-mutated string when changing dupped string" do
+    orig = +"a"
+    orig.setbyte 0, "b".ord
+    copy = orig.dup
+    orig.setbyte 0, "c".ord
+    orig.should == "c"
+    copy.should == "b"
+  end
+
+  it "returns a String in the same encoding as self" do
+    "hello".encode("US-ASCII").dup.encoding.should == Encoding::US_ASCII
+  end
+end