Reworked testing for all versions of the ExpireAfter operator, to i…

…mprove functional coverage and cover various existing defects. (#821)

src/DynamicData.Benchmarks/Cache/ExpireAfter_Cache_ForSource.cs

@@ -0,0 +1,62 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+using BenchmarkDotNet.Attributes;
+
+namespace DynamicData.Benchmarks.Cache;
+
+[MemoryDiagnoser]
+[MarkdownExporterAttribute.GitHub]
+public class ExpireAfter_Cache_ForSource
+{
+    public ExpireAfter_Cache_ForSource()
+        => _items = Enumerable
+            .Range(1, 1_000)
+            .Select(id => new Item()
+            {
+                Id = id
+            })
+            .ToArray();
+
+    [Benchmark]
+    [Arguments(1, 0)]
+    [Arguments(1, 1)]
+    [Arguments(10, 0)]
+    [Arguments(10, 1)]
+    [Arguments(10, 10)]
+    [Arguments(100, 0)]
+    [Arguments(100, 1)]
+    [Arguments(100, 10)]
+    [Arguments(100, 100)]
+    [Arguments(1_000, 0)]
+    [Arguments(1_000, 1)]
+    [Arguments(1_000, 10)]
+    [Arguments(1_000, 100)]
+    [Arguments(1_000, 1_000)]
+    public void AddsRemovesAndFinalization(int addCount, int removeCount)
+    {
+        using var source = new SourceCache<Item, int>(static item => item.Id);
+
+        using var subscription = source
+            .ExpireAfter(
+                timeSelector: static _ => TimeSpan.FromMinutes(60),
+                interval: null)
+            .Subscribe();
+
+        for (var i = 0; i < addCount; ++i)
+            source.AddOrUpdate(_items[i]);
+
+        for (var i = 0; i < removeCount; ++i)
+            source.RemoveKey(_items[i].Id);
+
+        subscription.Dispose();
+    }
+
+    private readonly IReadOnlyList<Item> _items;
+
+    private sealed class Item
+    {
+        public int Id { get; init; }
+    }
+}

src/DynamicData.Benchmarks/Cache/ExpireAfter_Cache_ForStream.cs

@@ -0,0 +1,87 @@
+using System;
+using System.Collections.Generic;
+using System.Reactive.Subjects;
+
+using BenchmarkDotNet.Attributes;
+
+namespace DynamicData.Benchmarks.Cache;
+
+[MemoryDiagnoser]
+[MarkdownExporterAttribute.GitHub]
+public class ExpireAfter_Cache_ForStream
+{
+    public ExpireAfter_Cache_ForStream()
+    {
+        var additions = new List<IChangeSet<Item, int>>(capacity: 1_000);
+        var removals = new List<IChangeSet<Item, int>>(capacity: 1_000);
+
+        for (var id = 1; id <= 1_000; ++id)
+        {
+            var item = new Item()
+            {
+                Id = id
+            };
+
+            additions.Add(new ChangeSet<Item, int>(capacity: 1)
+            {
+                new(reason: ChangeReason.Add,
+                    key: id,
+                    current: item)
+            });
+
+            removals.Add(new ChangeSet<Item, int>()
+            {
+                new(reason: ChangeReason.Remove,
+                    key: item.Id,
+                    current: item)
+            });
+        }
+
+        _additions = additions;
+        _removals = removals;
+    }
+
+    [Benchmark]
+    [Arguments(1, 0)]
+    [Arguments(1, 1)]
+    [Arguments(10, 0)]
+    [Arguments(10, 1)]
+    [Arguments(10, 10)]
+    [Arguments(100, 0)]
+    [Arguments(100, 1)]
+    [Arguments(100, 10)]
+    [Arguments(100, 100)]
+    [Arguments(1_000, 0)]
+    [Arguments(1_000, 1)]
+    [Arguments(1_000, 10)]
+    [Arguments(1_000, 100)]
+    [Arguments(1_000, 1_000)]
+    public void AddsRemovesAndFinalization(int addCount, int removeCount)
+    {
+        using var source = new Subject<IChangeSet<Item, int>>();
+
+        using var subscription = source
+            .ExpireAfter(static _ => TimeSpan.FromMinutes(60))
+            .Subscribe();
+
+        var itemLifetime = TimeSpan.FromMilliseconds(1);
+
+        var itemsToRemove = new List<Item>();
+
+        for (var i = 0; i < addCount; ++i)
+            source.OnNext(_additions[i]);
+
+        for (var i = 0; i < removeCount; ++i)
+            source.OnNext(_removals[i]);
+
+        subscription.Dispose();
+    }
+
+    private readonly IReadOnlyList<IChangeSet<Item, int>> _additions;
+    private readonly IReadOnlyList<IChangeSet<Item, int>> _removals;
+
+    private sealed class Item
+    {
+        public int Id { get; init; }
+    }
+}

src/DynamicData.Benchmarks/List/ExpireAfter_List.cs

@@ -0,0 +1,53 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+using BenchmarkDotNet.Attributes;
+
+namespace DynamicData.Benchmarks.List;
+
+[MemoryDiagnoser]
+[MarkdownExporterAttribute.GitHub]
+public class ExpireAfter_List
+{
+    public ExpireAfter_List()
+        => _items = Enumerable
+            .Range(0, 1_000)
+            .Select(_ => new object())
+            .ToArray();
+
+    [Benchmark]
+    [Arguments(1, 0)]
+    [Arguments(1, 1)]
+    [Arguments(10, 0)]
+    [Arguments(10, 1)]
+    [Arguments(10, 10)]
+    [Arguments(100, 0)]
+    [Arguments(100, 1)]
+    [Arguments(100, 10)]
+    [Arguments(100, 100)]
+    [Arguments(1_000, 0)]
+    [Arguments(1_000, 1)]
+    [Arguments(1_000, 10)]
+    [Arguments(1_000, 100)]
+    [Arguments(1_000, 1_000)]
+    public void AddsRemovesAndFinalization(int addCount, int removeCount)
+    {
+        using var source = new SourceList<object>();
+
+        using var subscription = source
+            .ExpireAfter(static _ => TimeSpan.FromMinutes(60), pollingInterval: null)
+            .Subscribe();
+
+        for (var i = 0; i < addCount; ++i)
+            source.Add(_items[i]);
+
+        var targetCount = addCount - removeCount;
+        while (source.Count > targetCount)
+            source.RemoveAt(0);
+
+        subscription.Dispose();
+    }
+
+    private readonly IReadOnlyList<object> _items;
+}