Refactor test assertions and minor test data cleanup

Updated RegexTests and SplitTests to simplify test data and assertions: replaced unnecessary ToArray() calls in SplitTests, switched to default! for null argument tests, and standardized InlineData string literals. These changes improve code clarity and reduce allocations in test code.

Author: electricessence

Tests/RegexTests.cs

@@ -48,7 +48,7 @@ public static void GroupNameTest()
 	[Theory]
 	[InlineData(@"\w+", "Hello, world! How are you?")]
 	[InlineData(@"\d+", "abc123def456ghi789")]
-	[InlineData(@"[aeiou]", "Hello World")]
+	[InlineData("[aeiou]", "Hello World")]
 	public static void AsSegments(string patternStr, string input)
 	{
 		var pattern = new Regex(patternStr);
@@ -64,6 +64,6 @@ public static void AsSegmentsNoAlloc_ThrowsOnNull()
 	{
 		var pattern = new Regex(@"\w+");
 		Assert.Throws<ArgumentNullException>(() => default(Regex)!.AsSegmentsNoAlloc("test"));
-		Assert.Throws<ArgumentNullException>(() => pattern.AsSegmentsNoAlloc(default(string)!));
+		Assert.Throws<ArgumentNullException>(() => pattern.AsSegmentsNoAlloc(default!));
 	}
 }

Tests/SplitTests.cs

@@ -163,9 +163,9 @@ public static void Split(string sequence, StringSplitOptions options = StringSpl
 	public static void SplitIgnoreCase(string sequence, string split, string expected, StringSplitOptions options = StringSplitOptions.None)
 	{
 		var segments = expected.Split(',');
-		Assert.Equal(segments, sequence.SplitToEnumerable(split, options, StringComparison.OrdinalIgnoreCase).ToArray());
-		Assert.Equal(segments, sequence.SplitAsMemory(split, options, StringComparison.OrdinalIgnoreCase).Select(m => m.Span.ToString()).ToArray());
-		Assert.Equal(segments, sequence.SplitAsSegments(split, options, StringComparison.OrdinalIgnoreCase).Select(m => m.ToString()).ToArray());
+		Assert.Equal(segments, sequence.SplitToEnumerable(split, options, StringComparison.OrdinalIgnoreCase));
+		Assert.Equal(segments, sequence.SplitAsMemory(split, options, StringComparison.OrdinalIgnoreCase).Select(m => m.Span.ToString()));
+		Assert.Equal(segments, sequence.SplitAsSegments(split, options, StringComparison.OrdinalIgnoreCase).Select(m => m.ToString()));
 		// NoAlloc variants
 		Assert.Equal(segments, sequence.SplitToEnumerableNoAlloc(split, options, StringComparison.OrdinalIgnoreCase).ToArray());
 		Assert.Equal(segments, sequence.SplitAsMemoryNoAlloc(split, options, StringComparison.OrdinalIgnoreCase).Select(m => m.Span.ToString()).ToArray());