Add a test that covers DateTimeOffset serialization

Author: brphelps

Octokit.GraphQL.Core.UnitTests/Models/Repository.cs

@@ -20,6 +20,7 @@ public Repository(Expression expression) : base(expression)
         public ID Id { get; }
         public string Name { get; }
         public Repository Parent => this.CreateProperty(x => x.Parent, Create);
+        public Issue IssueByCreation(Arg<DateTimeOffset> createdSince = default) => this.CreateMethodCall(x => x.IssueByCreation(createdSince), Models.Issue.Create);
         public Issue Issue(Arg<int> number) => this.CreateMethodCall(x => x.Issue(number), Models.Issue.Create);
         public IssueOrPullRequest IssueOrPullRequest(Arg<int> number) => this.CreateMethodCall(x => x.IssueOrPullRequest(number), Models.IssueOrPullRequest.Create);
         public IssueConnection Issues(Arg<int>? first = null, Arg<string>? after = null, Arg<int>? last = null, Arg<string>? before = null, Arg<IEnumerable<string>>? labels = null) => this.CreateMethodCall(x => x.Issues(first, after, last, before, labels), IssueConnection.Create);

Octokit.GraphQL.Core.UnitTests/QueryBuilderTests.cs

@@ -469,6 +469,21 @@ public void IntValue_Variable()
             Assert.Equal(expected, query.ToString(0));
         }
 
+        [Fact]
+        public void DateTimeOffsetValue_Variable()
+        {
+            var expected = "query{repository(owner:\"foo\",name:\"bar\"){issueByCreation(createdSince:\"2000-01-02T03:04:05+00:00\"){body}}}";
+
+            var expression = new Query()
+                .Repository("foo", "bar")
+                .IssueByCreation(new DateTimeOffset(2000,1,2,3,4,5, default))
+                .Select(x => x.Body);
+
+            var query = expression.Compile();
+
+            Assert.Equal(expected, query.ToString(0));
+        }
+
         [Fact]
         public void InputObject_Variable()
         {