Add test for date type

Author: meganemura

test/test_query_result.rb

@@ -60,6 +60,7 @@ class PersonType < GraphQL::Schema::Object
     field :company, String, null: true
     field :homepageURL, String, null: true, method: :homepage_url, camelize: false
     field :created_at, GraphQL::Types::ISO8601DateTime, null: false
+    field :created_on, GraphQL::Types::ISO8601Date, null: false
     field :hobbies, [String], null: true
     field :plan, PlanType, null: false
   end
@@ -103,6 +104,7 @@ def me
         last_name: "Peek",
         company: "GitHub",
         created_at: Time.at(0),
+        created_on: Date.new(1970, 1, 1),
         updated_at: Time.at(1),
         hobbies: ["soccer", "coding"],
         homepage_url: nil,
@@ -123,6 +125,7 @@ def issue_or_pull_request
             last_name: "Peek",
             company: "GitHub",
             created_at: Time.at(0),
+            created_on: Date.new(1970, 1, 1),
             updated_at: Time.at(1),
             hobbies: ["soccer", "coding"],
             plan: "LARGE"
@@ -605,6 +608,23 @@ def test_datetime_scalar_casting
     assert_equal Time.at(1), person.updated_at
   end
 
+  def test_date_scalar_casting
+    Temp.const_set :Query, @client.parse(<<-'GRAPHQL')
+      {
+        me {
+          name
+          createdOn
+        }
+      }
+    GRAPHQL
+
+    response = @client.query(Temp::Query)
+
+    person = response.data.me
+    assert_equal "Josh", person.name
+    assert_equal Date.new(1970, 1, 1), person.created_on
+  end
+
   include FooHelper
 
   def test_source_location