Testing rework: .ToObservableChangeSet() (#760)

* Rebuilt test fixtures for both `.ToObservableChangeSet()` operators, increasting code coverage from 69% to 100% across the internal implementation classes.

Identified existing defects within the `.ToObservableChangeSet()` operators, mostly related to error and completion propagation, and implemented testing for this behavior, with the tests being marked as "Skip" until the defects are fixed. This also includes the defect referred in #635.

Added an `IsCompleted` flag to `ChangeSetAggregator<T>`, to allow for testing of completion propagation.

* Added benchmarks for `.ToObservableChangeSet()` operators.

src/DynamicData.Benchmarks/Cache/ToObservableChangeSet_Cache.cs

@@ -0,0 +1,75 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reactive.Subjects;
+
+using BenchmarkDotNet.Attributes;
+using BenchmarkDotNet.Columns;
+
+namespace DynamicData.Benchmarks.Cache;
+
+[MemoryDiagnoser]
+[MarkdownExporterAttribute.GitHub]
+[HideColumns(Column.Ratio, Column.RatioSD, Column.AllocRatio)]
+public class ToObservableChangeSet_Cache
+{
+    public const int RngSeed
+        = 1234567;
+
+    public const int MaxItemCount
+        = 1000;
+
+    static ToObservableChangeSet_Cache()
+    {
+        _items = Enumerable.Range(1, MaxItemCount / 2)
+            .Select(id => new Item() { Id = id })
+            .ToArray();
+
+        var rng = new Random(RngSeed);
+
+        _itemIndexSequence = Enumerable.Range(1, MaxItemCount)
+            .Select(_ => rng.Next(maxValue: _items.Count))
+            .ToArray();
+    }
+
+    [Benchmark]
+    [Arguments(0, -1)]
+    [Arguments(0, 0)]
+    [Arguments(0, 1)]
+    [Arguments(1, 1)]
+    [Arguments(10, -1)]
+    [Arguments(10, 1)]
+    [Arguments(10, 5)]
+    [Arguments(10, 10)]
+    [Arguments(100, -1)]
+    [Arguments(100, 10)]
+    [Arguments(100, 50)]
+    [Arguments(100, 100)]
+    [Arguments(1_000, -1)]
+    [Arguments(1_000, 100)]
+    [Arguments(1_000, 500)]
+    [Arguments(1_000, 1_000)]
+    public void AddsUpdatesAndFinalization(int itemCount, int sizeLimit)
+    {
+        using var source = new Subject<Item>();
+
+        using var subscription = source
+            .ToObservableChangeSet(
+                keySelector: item => item.Id,
+                limitSizeTo: sizeLimit)
+            .Subscribe();
+
+        var indexModulus = (itemCount / 2) + 1;
+        for(var i = 0; i < itemCount; ++i)
+            source.OnNext(_items[_itemIndexSequence[i] % indexModulus]);
+        source.OnCompleted();
+    }
+
+    public class Item
+    {
+        public int Id { get; init; }
+    }
+
+    private static readonly IReadOnlyList<Item>    _items;
+    private static readonly IReadOnlyList<int>     _itemIndexSequence;
+}

src/DynamicData.Benchmarks/List/ToObservableChangeSet_List.cs

@@ -0,0 +1,44 @@
+using System;
+using System.Reactive.Subjects;
+
+using BenchmarkDotNet.Attributes;
+using BenchmarkDotNet.Columns;
+
+namespace DynamicData.Benchmarks.List;
+
+[MemoryDiagnoser]
+[MarkdownExporterAttribute.GitHub]
+[HideColumns(Column.Ratio, Column.RatioSD, Column.AllocRatio)]
+public class ToObservableChangeSet_List
+{
+    [Benchmark]
+    [Arguments(0, -1)]
+    [Arguments(0, 0)]
+    [Arguments(0, 1)]
+    [Arguments(1, 1)]
+    [Arguments(10, -1)]
+    [Arguments(10, 1)]
+    [Arguments(10, 5)]
+    [Arguments(10, 10)]
+    [Arguments(100, -1)]
+    [Arguments(100, 10)]
+    [Arguments(100, 50)]
+    [Arguments(100, 100)]
+    [Arguments(1_000, -1)]
+    [Arguments(1_000, 100)]
+    [Arguments(1_000, 500)]
+    [Arguments(1_000, 1_000)]
+    public void AddsUpdatesAndFinalization(int itemCount, int sizeLimit)
+    {
+        using var source = new Subject<int>();
+
+        using var subscription = source
+            .ToObservableChangeSet(limitSizeTo: sizeLimit)
+            .Subscribe();
+
+        var indexModulus = (itemCount / 2) + 1;
+        for(var i = 0; i < itemCount; ++i)
+            source.OnNext(i);
+        source.OnCompleted();
+    }
+}

src/DynamicData.Tests/API/ApiApprovalTests.DynamicDataTests.DotNet6_0.verified.txt

@@ -2638,6 +2638,7 @@ namespace DynamicData.Tests
         public ChangeSetAggregator(System.IObservable<DynamicData.IChangeSet<TObject>> source) { }
         public DynamicData.IObservableList<TObject> Data { get; }
         public System.Exception? Exception { get; set; }
+        public bool IsCompleted { get; }
         public System.Collections.Generic.IList<DynamicData.IChangeSet<TObject>> Messages { get; }
         public void Dispose() { }
         protected virtual void Dispose(bool isDisposing) { }

src/DynamicData.Tests/API/ApiApprovalTests.DynamicDataTests.DotNet7_0.verified.txt

@@ -2638,6 +2638,7 @@ namespace DynamicData.Tests
         public ChangeSetAggregator(System.IObservable<DynamicData.IChangeSet<TObject>> source) { }
         public DynamicData.IObservableList<TObject> Data { get; }
         public System.Exception? Exception { get; set; }
+        public bool IsCompleted { get; }
         public System.Collections.Generic.IList<DynamicData.IChangeSet<TObject>> Messages { get; }
         public void Dispose() { }
         protected virtual void Dispose(bool isDisposing) { }

src/DynamicData.Tests/API/ApiApprovalTests.DynamicDataTests.DotNet8_0.verified.txt

@@ -2638,6 +2638,7 @@ namespace DynamicData.Tests
         public ChangeSetAggregator(System.IObservable<DynamicData.IChangeSet<TObject>> source) { }
         public DynamicData.IObservableList<TObject> Data { get; }
         public System.Exception? Exception { get; set; }
+        public bool IsCompleted { get; }
         public System.Collections.Generic.IList<DynamicData.IChangeSet<TObject>> Messages { get; }
         public void Dispose() { }
         protected virtual void Dispose(bool isDisposing) { }