add test case for message model

app/models/message.rb

@@ -1,6 +1,8 @@
 class Message < ActiveRecord::Base
   belongs_to :from, :class_name => "User"
   belongs_to :to, :class_name => "User"
+  validates :from, presence: true
+  validates :to, presence: true
   validates :body, presence: true, length: { minimum: 5, maximum: 200 }
   validates :is_read, presence: true
 end

app/models/user.rb

@@ -1,6 +1,8 @@
 class User < ActiveRecord::Base
   has_many :posts
   has_many :comments
+  has_many :message_from, :class_name => "Message", :foreign_key => "from_id"
+  has_many :message_to, :class_name => "Message", :foreign_key => "to_id"
   before_save { self.email.downcase! }
   validates :name, presence: true, length: { maximum: 50 }
   VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i 

test/fixtures/users.yml

@@ -3,3 +3,8 @@ alice:
   name: Alice
   email: alice@test.com
   password_digest: <%= User.digest('badpassword') %>
+
+bob:
+  name: Bob
+  email: bob@test.com
+  password_digest: <%= User.digest('anotherbadpassword') %>

test/models/comment_test.rb

@@ -24,7 +24,7 @@ def setup
     assert_not @comment.valid?
   end
 
-  test "body should be present" do
+  test "comment should not be too short" do
     @comment.body = " " * 8
     assert_not @comment.valid?
   end

test/models/message_test.rb

@@ -4,4 +4,43 @@ class MessageTest < ActiveSupport::TestCase
   # test "the truth" do
   #   assert true
   # end
+  def setup
+    from, to = users("alice"), users("bob")
+    @message = Message.new(from: from, to: to,
+                           body: "samplemessage", is_read: 0)
+  end
+
+  test "should be vaild" do
+    assert @message.valid?
+  end
+
+  test "from should be present" do
+    @message.from = nil
+    assert_not @message.valid?
+  end
+
+  test "to should be present" do
+    @message.to = nil
+    assert_not @message.valid?
+  end
+
+  test "body should be present" do
+    @message.body = nil
+    assert_not @message.valid?
+  end
+
+  test "is_read should be present" do
+    @message.is_read = nil
+    assert_not @message.valid?
+  end
+
+  test "body should not be too short" do
+    @message.body = " " * 3
+    assert_not @message.valid?
+  end
+
+  test "body should not be too long" do
+    @message.body = "a" * 300
+    assert_not @message.valid?
+  end
 end