Add tests

#697

test/models/message_test.rb

@@ -0,0 +1,17 @@
+require 'test_helper'
+
+class MessageTest < ActiveSupport::TestCase
+  def setup
+    @message = messages(:greeting)
+  end
+
+  def test_valid
+    assert @message.valid?
+  end
+
+  def test_invalid_without_body
+    @message.body = nil
+    @message.validate
+    assert @message.invalid?
+  end
+end