From 805437c96e4c90777cf95755f19acefed9277544 Mon Sep 17 00:00:00 2001
From: Sergio Pedri <sergio0694@live.com>
Date: Sun, 28 Nov 2021 23:37:31 +0100
Subject: [PATCH] Add unit tests for Dictionary2<TKey, TValue>

---
 .../Internals/Test_Dictionary2.cs             | 170 ++++++++++++++++++
 1 file changed, 170 insertions(+)
 create mode 100644 tests/CommunityToolkit.Mvvm.UnitTests/Internals/Test_Dictionary2.cs

diff --git a/tests/CommunityToolkit.Mvvm.UnitTests/Internals/Test_Dictionary2.cs b/tests/CommunityToolkit.Mvvm.UnitTests/Internals/Test_Dictionary2.cs
new file mode 100644
index 00000000..a97053cd
--- /dev/null
+++ b/tests/CommunityToolkit.Mvvm.UnitTests/Internals/Test_Dictionary2.cs
@@ -0,0 +1,170 @@
+// 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.Runtime.CompilerServices;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace CommunityToolkit.Mvvm.UnitTests.Internals;
+
+[TestClass]
+public class Test_Dictionary2
+{
+    private static void AddItems<T>(T[] keys)
+        where T : IEquatable<T>
+    {
+        object[] values = Enumerable.Range(0, keys.Length).Select(static x => new object()).ToArray();
+
+        Dictionary2<T, object> dictionary = new();
+
+        // Go through all keys once
+        for (int i = 0; i < keys.Length; i++)
+        {
+            T key = keys[i];
+
+            // Verify the key doesn't exist yet
+            Assert.AreEqual(i, dictionary.Count);
+            Assert.IsFalse(dictionary.ContainsKey(key));
+            Assert.IsFalse(dictionary.TryGetValue(key, out object? obj));
+            Assert.IsNull(obj);
+            Assert.IsFalse(dictionary.TryRemove(key));
+
+            _ = Assert.ThrowsException<ArgumentException>(() => _ = dictionary[key]);
+
+            // This should create a new entry
+            ref object? value = ref dictionary.GetOrAddValueRef(key);
+
+            Assert.IsNull(value);
+
+            value = values[i];
+
+            // Verify the key now exists
+            Assert.IsTrue(dictionary.ContainsKey(key));
+            Assert.IsTrue(dictionary.TryGetValue(key, out obj));
+            Assert.AreSame(obj, value);
+            Assert.AreSame(obj, values[i]);
+
+            // Get the key again, should point to the same location
+            ref object? value2 = ref dictionary.GetOrAddValueRef(key);
+
+            Assert.IsTrue(Unsafe.AreSame(ref value, ref value2!));
+        }
+
+        Assert.AreEqual(keys.Length, dictionary.Count);
+
+        HashSet<T> keysSet = new();
+        HashSet<object> valuesSet = new();
+
+        Dictionary2<T, object>.Enumerator enumerator = dictionary.GetEnumerator();
+
+        // Gather all key/value pairs through the enumerator
+        while (enumerator.MoveNext())
+        {
+            Assert.IsTrue(keysSet.Add(enumerator.GetKey()));
+            Assert.IsTrue(valuesSet.Add(enumerator.GetValue()));
+        }
+
+        // Verify we have all values we expect
+        CollectionAssert.AreEquivalent(keys, keysSet.ToArray());
+        CollectionAssert.AreEquivalent(values, valuesSet.ToArray());
+
+        dictionary.Clear();
+
+        // Verify the dictionary was cleared properly
+        Assert.AreEqual(0, dictionary.Count);
+
+        enumerator = dictionary.GetEnumerator();
+
+        while (enumerator.MoveNext())
+        {
+            // Since the dictionary is now empty, we should never get here
+            Assert.Fail();
+        }
+    }
+
+    [TestMethod]
+    [DataRow(1)]
+    [DataRow(101)]
+    [DataRow(2467)]
+    public void AddItems_Int(int count)
+    {
+        AddItems(Enumerable.Range(0, count).ToArray());
+    }
+
+    [TestMethod]
+    [DataRow(1)]
+    [DataRow(101)]
+    [DataRow(2467)]
+    public void AddItems_String(int count)
+    {
+        AddItems(Enumerable.Range(0, count).Select(static x => x.ToString()).ToArray());
+    }
+
+    private static void TryRemoveItems<T>(T[] keys)
+        where T : IEquatable<T>
+    {
+        object[] values = Enumerable.Range(0, keys.Length).Select(static x => new object()).ToArray();
+
+        Dictionary2<T, object> dictionary = new();
+
+        // Populate the dictionary
+        for (int i = 0; i < keys.Length; i++)
+        {
+            T key = keys[i];
+
+            dictionary.GetOrAddValueRef(key) = values[i];
+        }
+
+        Random random = new(42);
+
+        keys = keys
+            .Select(x => (Key: x, Index: random.Next()))
+            .OrderBy(static x => x.Index)
+            .Select(static x => x.Key)
+            .ToArray();
+
+        values = keys.Select(k => dictionary[k]).ToArray();
+
+        for (int i = 0; i < keys.Length; i++)
+        {
+            T key = keys[i];
+
+            // Verify the state is consistent across removals
+            Assert.AreEqual(keys.Length - i, dictionary.Count);
+            Assert.IsTrue(dictionary.ContainsKey(key));
+            Assert.IsTrue(dictionary.TryGetValue(key, out object? obj));
+            Assert.AreSame(values[i], obj);
+
+            // Remove the item
+            Assert.IsTrue(dictionary.TryRemove(key));
+
+            // Verify the state is consistent after the removal
+            Assert.IsFalse(dictionary.ContainsKey(key));
+            Assert.IsFalse(dictionary.TryGetValue(key, out obj));
+            Assert.IsNull(obj);
+        }
+
+        Assert.AreEqual(0, dictionary.Count);
+    }
+
+    [TestMethod]
+    [DataRow(1)]
+    [DataRow(101)]
+    [DataRow(2467)]
+    public void TryRemoveItems_Int(int count)
+    {
+        TryRemoveItems(Enumerable.Range(0, count).ToArray());
+    }
+
+    [TestMethod]
+    [DataRow(1)]
+    [DataRow(101)]
+    [DataRow(2467)]
+    public void TryRemoveItems_String(int count)
+    {
+        TryRemoveItems(Enumerable.Range(0, count).Select(static x => x.ToString()).ToArray());
+    }
+}