Clean up tests, improve and test size estimation

Author: ResurrectedTrader

CLAUDE.md

@@ -135,7 +135,7 @@ Each section defines a `Magic` constant used for validation. Useful for debuggin
 
 ## Testing
 
-Tests use `MockExternalData` which provides hardcoded stat/item info for common test cases. For full integration testing, use `TxtFileExternalData` with real game data.
+All tests use `TxtFileExternalData.Default` which provides embedded stat/item info for versions 96, 97, and 99. For modded saves, use a custom `TxtFileExternalData` instance loaded from mod-specific .txt files.
 
 Round-trip tests verify that read -> write produces identical bytes.
 

SupportOlderVersions.md

@@ -462,7 +462,6 @@ These require careful implementation of the bit packing/unpacking logic. See dis
 | `src/D2SSharp/Data/TxtFileExternalData.cs` | Parse 1.09 columns |
 | `src/D2SSharp/Model/Item.cs` | Version-aware stat reading/writing |
 | `src/D2SSharp/Enums/StatId.cs` | Optional: legacy paired stats helper |
-| `src/D2SSharp.Tests/Mocks/MockExternalData.cs` | Update to return 1.09 columns |
 
 ---
 

src/D2SSharp.Tests/ConversionBinaryTests.cs

@@ -146,7 +146,7 @@ private int CompareSections(string name1, byte[] data1, uint version1,
             int size1 = pos1 - prev1;
             int size2 = pos2 - prev2;
             int diff = size2 - size1;
-            string diffStr = diff == 0 ? "=" : (diff > 0 ? $"+{diff}" : diff.ToString());
+            string diffStr = diff == 0 ? "=" : diff > 0 ? $"+{diff}" : diff.ToString();
 
             bool sizeMatch = size1 == size2;
             bool contentMatch = false;
@@ -184,9 +184,9 @@ private int CompareSections(string name1, byte[] data1, uint version1,
                         if (section1[j] != section2[j])
                         {
                             string ignoreReason = isIgnored
-                                ? (sectionName == "Items"
+                                ? sectionName == "Items"
                                     ? " (ignored: items compared separately, ordering may differ)"
-                                    : " (ignored: checksum differs due to item ordering)")
+                                    : " (ignored: checksum differs due to item ordering)"
                                 : "";
                             _output.WriteLine($"  ^ First diff at offset {j}: 0x{section1[j]:X2} vs 0x{section2[j]:X2}{ignoreReason}");
                             break;