🧪 Add StringExtensions unit tests

tests/GameUtils.Tests/Extensions/StringExtensionsTests.cs

@@ -0,0 +1,56 @@
+using System;
+using GameUtils.Extensions;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace GameUtils.Tests.Extensions;
+
+[TestClass]
+public class StringExtensionsTests
+{
+    [TestMethod]
+    [DataRow("hello", 0, true, 'h')]
+    [DataRow("hello", 4, true, 'o')]
+    [DataRow("hello", -1, false, '\0')]
+    [DataRow("hello", 5, false, '\0')]
+    [DataRow("", 0, false, '\0')]
+    public void TryGet_ReturnsExpectedResult(string str, int index, bool expectedReturn, char expectedChar)
+    {
+        var result = str.TryGet(index, out char c);
+        Assert.AreEqual(expectedReturn, result);
+        Assert.AreEqual(expectedChar, c);
+    }
+
+    [TestMethod]
+    public void TryGet_NullString_ThrowsArgumentNullException()
+    {
+        string str = null!;
+        Assert.ThrowsExactly<ArgumentNullException>(() => str.TryGet(0, out _));
+    }
+
+    [TestMethod]
+    [DataRow("hello", 3, "hellohellohello")]
+    [DataRow("a", 5, "aaaaa")]
+    [DataRow("abc", 1, "abc")]
+    [DataRow("test", 0, "")]
+    [DataRow("", 5, "")]
+    [DataRow("", 0, "")]
+    public void Repeat_ReturnsExpectedResult(string str, int count, string expectedResult)
+    {
+        var result = str.Repeat(count);
+        Assert.AreEqual(expectedResult, result);
+    }
+
+    [TestMethod]
+    public void Repeat_NullString_ThrowsArgumentNullException()
+    {
+        string str = null!;
+        Assert.ThrowsExactly<ArgumentNullException>(() => str.Repeat(5));
+    }
+
+    [TestMethod]
+    public void Repeat_NegativeCount_ThrowsArgumentOutOfRangeException()
+    {
+        string str = "test";
+        Assert.ThrowsExactly<ArgumentOutOfRangeException>(() => str.Repeat(-1));
+    }
+}