Add a simple model representing a terminal snapshot

app/models/snapshot.rb

@@ -0,0 +1,21 @@
+class Snapshot
+  attr_reader :lines
+
+  def initialize(lines = [])
+    @lines = lines
+  end
+
+  def ==(other)
+    other.lines == lines
+  end
+
+  class Serializer
+    def dump(snapshot)
+      YAML.dump(snapshot.lines)
+    end
+
+    def load(value)
+      value.present? ? Snapshot.new(YAML.load(value)) : Snapshot.new
+    end
+  end
+end

spec/models/snapshot_spec.rb

@@ -0,0 +1,23 @@
+require 'spec_helper'
+
+describe Snapshot do
+
+  describe '#==' do
+    let(:snapshot) { Snapshot.new([:foo]) }
+
+    subject { snapshot == other }
+
+    context "when the other has the same lines" do
+      let(:other) { Snapshot.new([:foo]) }
+
+      it { should be(true) }
+    end
+
+    context "when the other has a different lines" do
+      let(:other) { Snapshot.new([:foo, :bar]) }
+
+      it { should be(false) }
+    end
+  end
+
+end