Refactored tests for nulls/default query string parameters; removed some duplication and fixed an equality bug.

Author: Bart Koelman

src/JsonApiDotNetCore/Serialization/Building/ResourceObjectBuilder.cs

@@ -146,7 +146,7 @@ private void ProcessAttributes(IIdentifiable resource, IEnumerable<AttrAttribute
                     return;
                 }
 
-                if (_settings.SerializerDefaultValueHandling == DefaultValueHandling.Ignore && value == TypeHelper.GetDefaultValue(attr.Property.PropertyType))
+                if (_settings.SerializerDefaultValueHandling == DefaultValueHandling.Ignore && Equals(value, TypeHelper.GetDefaultValue(attr.Property.PropertyType)))
                 {
                     return;
                 }

test/JsonApiDotNetCoreExampleTests/Acceptance/Extensibility/IgnoreDefaultValuesTests.cs

@@ -0,0 +1,18 @@
+using System;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreExampleTests.IntegrationTests.QueryStrings
+{
+    public sealed class Appointment : Identifiable
+    {
+        [Attr]
+        public string Title { get; set; }
+
+        [Attr]
+        public DateTimeOffset StartTime { get; set; }
+
+        [Attr]
+        public DateTimeOffset EndTime { get; set; }
+    }
+}

test/JsonApiDotNetCoreExampleTests/Acceptance/Extensibility/IgnoreNullValuesTests.cs

@@ -0,0 +1,18 @@
+using System.Collections.Generic;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreExampleTests.IntegrationTests.QueryStrings
+{
+    public sealed class Calendar : Identifiable
+    {
+        [Attr]
+        public string TimeZone { get; set; }
+
+        [Attr]
+        public int DefaultAppointmentDurationInMinutes { get; set; }
+
+        [HasMany]
+        public ISet<Appointment> Appointments { get; set; }
+    }
+}