Add syncronus and asyncronus tests for the incremtnetal loading collection

Author: Rosuavio

UnitTests/UnitTests.UWP/UI/Collection/DataSource.cs

@@ -0,0 +1,43 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Toolkit.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace UnitTests.UI
+{
+    public class DataSource<T> : IIncrementalSource<T>
+    {
+        private readonly IEnumerable<T> _data;
+
+        public DataSource(IEnumerable<T> items)
+        {
+            _data = items;
+        }
+
+        public async Task<IEnumerable<T>> GetPagedItemsAsync(int pageIndex, int pageSize, CancellationToken cancellationToken = default(CancellationToken))
+        {
+            // Gets items from the collection according to pageIndex and pageSize parameters.
+            var result = (from p in _data
+                          select p).Skip(pageIndex * pageSize).Take(pageSize);
+
+            // Simulates a longer request...
+            // Make sure the list is still in order after a refresh,
+            // even if the first page takes longer to load
+            if (pageIndex == 0)
+            {
+                await Task.Delay(2500);
+            }
+            else
+            {
+                await Task.Delay(1000);
+            }
+
+            return result;
+        }
+    }
+}

UnitTests/UnitTests.UWP/UI/Collection/Test_IncrementalLoadingCollection.cs

@@ -0,0 +1,54 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.Toolkit.Uwp;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace UnitTests.UI
+{
+    [TestClass]
+    public class Test_IncrementalLoadingCollection
+    {
+        [TestMethod]
+        public async Task SequentialRequests()
+        {
+            const int pageSize = 20;
+            const int pages = 5;
+            var collection = new IncrementalLoadingCollection<DataSource<int>, int>(new DataSource<int>(Enumerable.Range(0, pageSize * pages)), pageSize);
+
+            for (int pageNum = 1; pageNum <= pages; pageNum++)
+            {
+                var rez1 = await collection.LoadMoreItemsAsync(0);
+                Assert.AreEqual((uint)pageSize, rez1.Count);
+                CollectionAssert.AreEquivalent(Enumerable.Range(0, pageSize * pageNum).ToArray(), collection);
+            }
+        }
+
+        [TestMethod]
+        public void ConcurentRequests()
+        {
+            const int pageSize = 20;
+            const int pages = 5;
+            var collection = new IncrementalLoadingCollection<DataSource<int>, int>(new DataSource<int>(Enumerable.Range(0, pageSize * pages)), pageSize);
+
+            var requests = new List<Task>();
+
+            for (int pageNum = 1; pageNum <= pages; pageNum++)
+            {
+                requests.Add(collection.LoadMoreItemsAsync(0).AsTask().ContinueWith(t =>
+                {
+                    Assert.AreEqual(TaskStatus.RanToCompletion, t.Status);
+                    Assert.AreEqual((uint)pageSize, t.Result.Count);
+                }));
+            }
+
+            Task.WaitAll(requests.ToArray());
+            CollectionAssert.AreEquivalent(Enumerable.Range(0, pageSize * pages).ToArray(), collection);
+        }
+    }
+}

UnitTests/UnitTests.UWP/UnitTests.UWP.csproj

@@ -197,6 +197,8 @@
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Helpers\Test_WeakEventListener.cs" />
     <Compile Include="UI\Animations\Test_AnimationBuilderStart.cs" />
+    <Compile Include="UI\Collection\DataSource.cs" />
+    <Compile Include="UI\Collection\Test_IncrementalLoadingCollection.cs" />
     <Compile Include="UI\Controls\Test_Carousel.cs" />
     <Compile Include="UI\Controls\Test_BladeView.cs" />
     <Compile Include="UI\Controls\Test_RadialGauge.cs" />
@@ -548,4 +550,4 @@
   <Target Name="AfterBuild">
   </Target>
   -->
-</Project>
+</Project>