Update LinesScrubberTests.cs

Author: SimonCropp

src/Verify.Tests/LinesScrubberTests.cs

@@ -312,4 +312,154 @@ public void FilterLines_MultipleConsecutiveRemoved()
 
         Assert.Equal("keep1\nkeep2", builder.ToString());
     }
+
+    [Fact]
+    public void FilterLines_LineSpansMultipleChunks()
+    {
+        // StringBuilder default chunk size is ~8000 chars
+        // Create a line that's definitely longer than a chunk
+        var longLine = new string('a', 10_000);
+        var builder = new StringBuilder();
+        builder.Append("keep1\n");
+        builder.Append(longLine);
+        builder.Append("\nkeep2");
+
+        builder.FilterLines(line => line == longLine);
+
+        Assert.Equal("keep1\nkeep2", builder.ToString());
+    }
+
+    [Fact]
+    public void FilterLines_NewlineAtChunkBoundary()
+    {
+        // Fill first chunk, then add newline at boundary
+        var chunkFiller = new string('x', 8000);
+        var builder = new StringBuilder();
+        builder.Append(chunkFiller);
+        builder.Append('\n');
+        builder.Append("line2");
+
+        builder.FilterLines(line => line == chunkFiller);
+
+        Assert.Equal("line2", builder.ToString());
+    }
+
+    [Fact]
+    public void FilterLines_CrLfSplitAcrossChunks()
+    {
+        // Create scenario where \r is at end of one chunk and \n at start of next
+        var lineContent = new string('y', 7999);
+        var builder = new StringBuilder();
+        builder.Append(lineContent);
+        builder.Append("\r\n");
+        builder.Append("nextline");
+
+        builder.FilterLines(line => line == lineContent);
+
+        Assert.Equal("nextline", builder.ToString());
+    }
+
+    [Fact]
+    public void FilterLines_MultipleLinesSpanningChunks()
+    {
+        var builder = new StringBuilder();
+        var lines = new List<string>();
+
+        // Create lines of varying lengths that will span chunk boundaries
+        for (var i = 0; i < 20; i++)
+        {
+            var line = $"line{i}_" + new string((char) ('a' + i % 26), 1000 + i * 100);
+            lines.Add(line);
+            builder.Append(line);
+            if (i < 19)
+            {
+                builder.Append('\n');
+            }
+        }
+
+        // Remove even-indexed lines
+        builder.FilterLines(line => lines.IndexOf(line) % 2 == 0);
+
+        var expected = string.Join('\n', lines.Where((_, i) => i % 2 == 1));
+        Assert.Equal(expected, builder.ToString());
+    }
+
+    [Fact]
+    public void FilterLines_VeryLongLineKept()
+    {
+        var longLine = new string('z', 20_000);
+        var builder = new StringBuilder();
+        builder.Append("remove\n");
+        builder.Append(longLine);
+        builder.Append("\nremove");
+
+        builder.FilterLines(line => line == "remove");
+
+        Assert.Equal(longLine, builder.ToString());
+    }
+
+    [Fact]
+    public void FilterLines_MultipleChunksAllRemoved()
+    {
+        var builder = new StringBuilder();
+        for (var i = 0; i < 10; i++)
+        {
+            builder.Append(new string('a', 2000));
+            builder.Append('\n');
+        }
+
+        builder.FilterLines(_ => true);
+
+        Assert.Equal(string.Empty, builder.ToString());
+    }
+
+    [Fact]
+    public void FilterLines_MultipleChunksNoneRemoved()
+    {
+        var builder = new StringBuilder();
+        for (var i = 0; i < 10; i++)
+        {
+            var line = new string((char) ('a' + i), 2000);
+            builder.Append(line);
+            builder.Append('\n');
+        }
+
+        var original = builder.ToString();
+
+        builder.FilterLines(_ => false);
+
+        Assert.Equal(original, builder.ToString());
+    }
+
+    [Fact]
+    public void FilterLines_ChunkBoundaryInMiddleOfLine()
+    {
+        // Specifically target chunk boundary within line content
+        var prefix = new string('p', 7990);
+        var suffix = new string('s', 100);
+        var fullLine = prefix + suffix;
+
+        var builder = new StringBuilder();
+        builder.Append("before\n");
+        builder.Append(fullLine);
+        builder.Append("\nafter");
+
+        builder.FilterLines(line => line == "before");
+
+        Assert.Equal(fullLine + "\nafter", builder.ToString());
+    }
+
+    [Fact]
+    public void FilterLines_EmptyLinesAroundChunkBoundaries()
+    {
+        var longLine = new string('x', 8000);
+        var builder = new StringBuilder();
+        builder.Append(longLine);
+        builder.Append("\n\n\n");
+        builder.Append("keep");
+
+        builder.FilterLines(string.IsNullOrEmpty);
+
+        Assert.Equal(longLine + "\nkeep", builder.ToString());
+    }
 }