Add & improve string extensions and add tests

src/CuteUtils.Tests/Misc/StringExtTests.cs

@@ -0,0 +1,161 @@
+using CuteUtils.Misc;
+
+namespace CuteUtils.Tests.Misc;
+
+[TestClass]
+public class StringExtTests_Coverage
+{
+    [TestMethod]
+    public void ToFileName_EmptyAndNull_ReturnsEmptyOrThrows()
+    {
+        Assert.AreEqual("", "".ToFileName());
+        Assert.AreEqual("", "".ToFileName(allowSpaces: false));
+
+        string? nullStr = null;
+        _ = Assert.ThrowsExactly<NullReferenceException>(() => nullStr!.ToFileName());
+    }
+
+    [TestMethod]
+    public void ToFileName_NormalizesUnicodeAccents()
+    {
+        string input = "Ångström Îñţérñåţîöñåļ";
+        string output = input.ToFileName();
+
+        Assert.IsFalse(output.Any(c => c > 127));  // no extended unicode
+        Assert.Contains("An", output);       // Å -> A + n (typical decompose)
+    }
+
+    [TestMethod]
+    public void ToFileName_LongString_TrimsProperly()
+    {
+        string longInput = new('x', 500);
+        string result = longInput.ToFileName();
+
+        Assert.IsLessThanOrEqualTo(255, result.Length, "File name should be trimmed to FS-safe length");
+    }
+
+    [TestMethod]
+    public void ToPath_EmptyAndNull_ReturnsEmptyOrThrows()
+    {
+        Assert.AreEqual("", "".ToPath());
+
+        string? nullStr = null;
+        _ = Assert.ThrowsExactly<NullReferenceException>(() => nullStr!.ToPath());
+    }
+
+    [TestMethod]
+    public void ToPath_RemovesBothFileAndPathInvalidChars()
+    {
+        string input = "t<>e\"s|t/dir\\name:*?";
+        string output = input.ToPath();
+
+        foreach (char c in Path.GetInvalidPathChars())
+        {
+            Assert.DoesNotContain(c, output);
+        }
+    }
+
+    [TestMethod]
+    public void Truncate_HandlesNull_Throws()
+    {
+        string? nullStr = null;
+        _ = Assert.ThrowsExactly<NullReferenceException>(() => nullStr!.Truncate(5));
+    }
+
+    [TestMethod]
+    public void Truncate_LongString_Performance()
+    {
+        string longStr = new('x', 10_000);
+        string result = longStr.Truncate(100);
+
+        Assert.AreEqual(100, result.Length);
+    }
+
+    [TestMethod]
+    public void CorrectNewLine_EmptyString_ReturnsEmpty()
+    {
+        Assert.AreEqual("", "".CorrectNewLine());
+    }
+
+    [TestMethod]
+    public void CorrectNewLine_Mixed_Newlines_Normalizes()
+    {
+        string mixed = "a\r\nb\nc\rd";
+
+        string result = mixed.CorrectNewLine();
+
+        if (Environment.OSVersion.Platform == PlatformID.Unix)
+        {
+            Assert.AreEqual("a\nb\nc\nd", result);
+        }
+        else
+        {
+            Assert.AreEqual("a\r\nb\r\nc\r\nd", result);
+        }
+    }
+
+    [TestMethod]
+    public void RemoveWhitespaces_UnicodeSpaces()
+    {
+        string input = "a\u2003b\u3000c"; // em-space, ideographic space
+        Assert.AreEqual("abc", input.RemoveWhitespaces());
+    }
+
+    [TestMethod]
+    public void Reverse_EmptyAndSingleCharacter()
+    {
+        Assert.AreEqual("", "".Reverse());
+        Assert.AreEqual("a", "a".Reverse());
+    }
+
+    [TestMethod]
+    public void Reverse_UnicodeCombiningCharacters()
+    {
+        string input = "e\u0301"; // é composed as e + diacritic
+        string result = input.Reverse();
+
+        Assert.AreEqual("\u0301e", result);
+    }
+
+    [TestMethod]
+    public void ReplaceCaseInsensitive_UnicodeCase()
+    {
+        string input = "Straße"; // Eszett
+        string replaced = input.ReplaceCaseInsensitive("ß", "ss");
+
+        Assert.AreEqual("Strasse", replaced);
+    }
+
+    [TestMethod]
+    public void ReplaceCaseInsensitive_ReplacesOverlappingCorrectly()
+    {
+        string input = "aaaa";
+        string replaced = input.ReplaceCaseInsensitive("aa", "b");
+
+        Assert.AreEqual("bb", replaced); // correct non-overlapping behavior
+    }
+
+    [TestMethod]
+    public void RemoveDiacritics_RemovesAccents_PreservesBaseCharacters()
+    {
+        // composed character
+        string caf = "café";
+        Assert.AreEqual("cafe", caf.RemoveDiacritics());
+
+        // another composed example (Å -> A or Ang depending on normalization)
+        string ang = "Ångström";
+        Assert.AreEqual("Angstrom", ang.RemoveDiacritics());
+
+        // decomposed form: e + combining acute accent
+        string decomposed = "e\u0301"; // e + ◌́
+        Assert.AreEqual("e", decomposed.RemoveDiacritics());
+
+        // empty string stays empty
+        Assert.AreEqual(string.Empty, string.Empty.RemoveDiacritics());
+
+        // null behavior: current implementation will throw NullReferenceException
+        string? nullStr = null;
+        _ = Assert.ThrowsExactly<NullReferenceException>(() => nullStr!.RemoveDiacritics());
+    }
+
+}