WordOccurrenceCounter: Implement thread-safe word counting

Task1/WordOccurrenceCounter.Tests/WordCounterTests.cs

@@ -0,0 +1,27 @@
+namespace WordOccurrenceCounter.Tests;
+
+public class WordCounterTests
+{
+    [Test]
+    public void AddToCount_Parallel_ShouldCountCorrectly()
+    {
+        var wordCounter = new WordCounter();
+        var words = new[] { "test", "example", "parallel", "test", "example", "test" };
+        int iterations = 1000;
+
+        Parallel.For(0, iterations, i =>
+        {
+            foreach (var word in words)
+            {
+                wordCounter.AddToCount(word);
+            }
+        });
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(wordCounter.GetCount("test"), Is.EqualTo(iterations * 3));
+            Assert.That(wordCounter.GetCount("example"), Is.EqualTo(iterations * 2));
+            Assert.That(wordCounter.GetCount("parallel"), Is.EqualTo(iterations * 1));
+        });
+    }
+}

Task1/WordOccurrenceCounter.Tests/WordOccurrenceCounter.Tests.csproj

@@ -17,6 +17,10 @@
     <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />
   </ItemGroup>
 
+  <ItemGroup>
+    <ProjectReference Include="..\WordOccurrenceCounter\WordOccurrenceCounter.csproj" />
+  </ItemGroup>
+
   <ItemGroup>
     <Using Include="NUnit.Framework" />
   </ItemGroup>

Task1/WordOccurrenceCounter/IWordCounter.cs

@@ -0,0 +1,10 @@
+namespace WordOccurrenceCounter;
+
+public interface IWordCounter
+{
+    void AddToCount(string word);
+
+    int GetCount(string word);
+
+    IReadOnlyDictionary<string, int> GetCounts();
+}

Task1/WordOccurrenceCounter/WordCounter.cs

@@ -1,12 +1,30 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+using System.Collections.Concurrent;
 
 namespace WordOccurrenceCounter;
 
-public class WordCounter
+public class WordCounter : IWordCounter
 {
+    private const int InitialValue = 1;
 
+    private readonly ConcurrentDictionary<string, int> _wordCounts;
+
+    public WordCounter()
+    {
+        _wordCounts = new ConcurrentDictionary<string, int>();
+    }
+
+    public void AddToCount(string word)
+    {
+        _wordCounts.AddOrUpdate(word, _ => InitialValue, (_, count) => count + 1);
+    }
+
+    public int GetCount(string word)
+    {
+        return _wordCounts.TryGetValue(word, out var count) ? count : 0;
+    }
+
+    public IReadOnlyDictionary<string, int> GetCounts()
+    {
+        return _wordCounts;
+    }
 }