1 files changed, 52 insertions, 0 deletions
diff --git a/spec/ruby/core/array/pack/buffer_spec.rb b/spec/ruby/core/array/pack/buffer_spec.rb
new file mode 100644
index 0000000000..928f7db731
--- /dev/null
+++ b/spec/ruby/core/array/pack/buffer_spec.rb
@@ -0,0 +1,52 @@
+# encoding: ascii-8bit
+
+require File.expand_path('../../../../spec_helper', __FILE__)
+
+ruby_version_is '2.4' do
+  describe "Aray#pack with `buffer` option" do
+    it "returns specified buffer" do
+      n = [ 65, 66, 67 ]
+      buffer = " "*3
+      result = n.pack("ccc", buffer: buffer)      #=> "ABC"
+      result.should equal(buffer)
+    end
+
+    it "adds result at the end of buffer content" do
+      n = [ 65, 66, 67 ] # result without buffer is "ABC"
+
+      buffer = ""
+      n.pack("ccc", buffer: buffer).should == "ABC"
+
+      buffer = "123"
+      n.pack("ccc", buffer: buffer).should == "123ABC"
+
+      buffer = "12345"
+      n.pack("ccc", buffer: buffer).should == "12345ABC"
+    end
+
+    it "raises TypeError exception if buffer is not String" do
+      lambda { [65].pack("ccc", buffer: []) }.should raise_error(
+        TypeError, "buffer must be String, not Array")
+    end
+
+    context "offset (@) is specified" do
+      it 'keeps buffer content if it is longer than offset' do
+        n = [ 65, 66, 67 ]
+        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"
+        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"
+        n.pack("@3ccc", buffer: buffer).should == "123ABC"
+      end
+    end
+  end
+end