Add a spec for encoding and decoding a message

Author: dasch

spec/protocol/message_spec.rb

@@ -0,0 +1,16 @@
+describe Kafka::Protocol::Message do
+  it "encodes and decodes messages" do
+    message = Kafka::Protocol::Message.new(
+      value: "yolo",
+      key: "xx",
+    )
+
+    io = StringIO.new
+    encoder = Kafka::Protocol::Encoder.new(io)
+    message.encode(encoder)
+    data = StringIO.new(io.string)
+    decoder = Kafka::Protocol::Decoder.new(data)
+
+    expect(Kafka::Protocol::Message.decode(decoder)).to eq message
+  end
+end