Added test project

 - Added tests for the BasicUnscrambler
 - Added a fixture for sharing the list of words between tests

Unscrambler.Tests/BasicUnscramblerTests.cs

@@ -0,0 +1,59 @@
+using System.Diagnostics;
+using Xunit.Abstractions;
+
+namespace Unscrambler.Tests;
+
+[Collection("FindWords")]
+public class BasicUnscramblerTests
+{
+    private readonly ITestOutputHelper _output;
+    private readonly WordListFixture _fixture;
+
+    // Load words
+    public BasicUnscramblerTests(ITestOutputHelper output, WordListFixture fixture)
+    {
+        _output = output;
+        _fixture = fixture;
+    }
+
+    [Theory]
+    [InlineData("letters", 7)]
+    [InlineData("resources", 10)]
+    [InlineData("unscrambler", 12)]
+    [InlineData("computer", 10)]
+    [InlineData("programming", 6)]
+    [InlineData("csharp", 4)]
+    [InlineData("dotnet", 2)]
+    [InlineData("visualstudio", 5)]
+    [InlineData("test", 4)]
+
+    public void CheckForWords(string letters, int maxLength)
+    {
+        // Find all words using brute force
+        var startTime = Stopwatch.GetTimestamp();
+        var checkList = _fixture.FindAllWordsUsingBruteForce(letters.ToCharArray(), maxLength);
+        var bruteForceTimespan = Stopwatch.GetElapsedTime(startTime);
+
+        // Find all words using the Unscrambler
+        startTime = Stopwatch.GetTimestamp();
+        var unscrambled = _fixture._unscrambler.Unscramble(letters.ToCharArray(), maxLength);
+        var unscrambleTimespan = Stopwatch.GetElapsedTime(startTime);
+
+        // Output how long each method took
+
+        _output.WriteLine($"Brute force took {bruteForceTimespan.TotalMicroseconds} us");
+        _output.WriteLine($"Unscramble took {unscrambleTimespan.TotalMicroseconds} us");
+
+        // Output how many times faster unscramble is than brute force
+        _output.WriteLine($"Unscramble is {Math.Round(bruteForceTimespan.TotalMicroseconds / unscrambleTimespan.TotalMicroseconds, 3)} times faster than brute force");
+
+        // Check that the unscrambler found all the words
+        Assert.Equal(checkList.Count, unscrambled.Count);
+
+        foreach(var word in checkList)
+        {
+            Assert.Contains(word, unscrambled);
+            _output.WriteLine("Found: " + word);
+        }
+    }
+}

Unscrambler.Tests/GlobalUsings.cs

@@ -0,0 +1 @@
+global using Xunit;

Unscrambler.Tests/Unscrambler.Tests.csproj

@@ -0,0 +1,29 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+
+    <IsPackable>false</IsPackable>
+    <IsTestProject>true</IsTestProject>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
+    <PackageReference Include="xunit" Version="2.6.6" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.6">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
+    <PackageReference Include="coverlet.collector" Version="6.0.0">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Unscrambler\Unscrambler.csproj" />
+  </ItemGroup>
+
+</Project>

Unscrambler.Tests/WordListFixture.cs

@@ -0,0 +1,76 @@
+using Unscrambler.Basic;
+
+namespace Unscrambler.Tests
+{
+    [CollectionDefinition("FindWords")]
+    public class FindWordsCollection : ICollectionFixture<WordListFixture>
+    {
+        // This class has no code, and is never created. Its purpose is simply
+        // to be the place to apply [CollectionDefinition] and all the
+        // ICollectionFixture<> interfaces.
+    }
+
+    /// <summary>
+    /// Use this class to load the word list and unscrambler once for all tests. This will speed up the tests.<br/>
+    /// It also moves the code for loading words, from the test file to this fixture.
+    /// </summary>
+    public class WordListFixture
+    {
+        // Url to the word list. You can update the word list by changing this url to a different word list, and removing the local file.
+        public const string WordListUrl = "https://github.com/dolph/dictionary/raw/master/popular.txt";
+        // Path to the word list. This is where the word list will be downloaded to.
+        public const string WordListPath = "popular.txt";
+
+        public readonly string[] _words;
+        public readonly BasicUnscrambler _unscrambler = new();
+
+        public WordListFixture()
+        {
+            // Check if the word list exists. If it doesn't, download it.
+            if (!File.Exists(WordListPath))
+            {
+                using var client = new HttpClient();
+                var bytes = client.GetByteArrayAsync(WordListUrl).Result;
+                File.WriteAllBytes(WordListPath, bytes);
+            }
+
+            _words = File.ReadAllLines(WordListPath);
+
+            // Add words to unscrambler
+            foreach (var word in _words)
+            {
+                _unscrambler.AddWord(word);
+            }
+        }
+
+        /// <summary>
+        /// Finds all words using brute force.
+        /// </summary>
+        public HashSet<string> FindAllWordsUsingBruteForce(char[] letters, int maxLength)
+        {
+            var words = new HashSet<string>(100);
+            foreach (var word in _words)
+            {
+                if (word.Length > maxLength)
+                {
+                    continue;
+                }
+                var lettersCopy = letters.ToList();
+                var isMatch = true;
+                foreach (var letter in word)
+                {
+                    if (!lettersCopy.Remove(letter))
+                    {
+                        isMatch = false;
+                        break;
+                    }
+                }
+                if (isMatch)
+                {
+                    words.Add(word);
+                }
+            }
+            return words;
+        }
+    }
+}

Unscrambler.sln

@@ -7,6 +7,8 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Unscrambler", "Unscrambler\
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Benchmarks", "Benchmarks\Benchmarks.csproj", "{1520FA33-A1F0-41A4-B6EE-4F24C478A422}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Unscrambler.Tests", "Unscrambler.Tests\Unscrambler.Tests.csproj", "{993E5B97-E360-4F60-8AFD-E8D89C5755CD}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -21,6 +23,10 @@ Global
 		{1520FA33-A1F0-41A4-B6EE-4F24C478A422}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{1520FA33-A1F0-41A4-B6EE-4F24C478A422}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{1520FA33-A1F0-41A4-B6EE-4F24C478A422}.Release|Any CPU.Build.0 = Release|Any CPU
+		{993E5B97-E360-4F60-8AFD-E8D89C5755CD}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{993E5B97-E360-4F60-8AFD-E8D89C5755CD}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{993E5B97-E360-4F60-8AFD-E8D89C5755CD}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{993E5B97-E360-4F60-8AFD-E8D89C5755CD}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE