diff --git a/TestData/Generated/Individual/PCB/BODY_3D_STEP_CHECKSUM0.PcbLib b/TestData/Generated/Individual/PCB/BODY_3D_STEP_CHECKSUM0.PcbLib
deleted file mode 100644
index ef8181d..0000000
Binary files a/TestData/Generated/Individual/PCB/BODY_3D_STEP_CHECKSUM0.PcbLib and /dev/null differ
diff --git a/tests/COVERAGE.md b/tests/COVERAGE.md
index e4161d2..68697af 100644
--- a/tests/COVERAGE.md
+++ b/tests/COVERAGE.md
@@ -1,7 +1,5 @@
 # Property Coverage Report
 
-Generated: 2026-06-19 09:47 UTC
-
 ## PCB Primitive Types
 
 | Type | Files | Primitives | JSON Props | Mapped | Missing | Coverage |
diff --git a/tests/OriginalCircuit.Altium.Tests/PropertyCoverage/CoverageReportTests.cs b/tests/OriginalCircuit.Altium.Tests/PropertyCoverage/CoverageReportTests.cs
index e163a2b..8b21304 100644
--- a/tests/OriginalCircuit.Altium.Tests/PropertyCoverage/CoverageReportTests.cs
+++ b/tests/OriginalCircuit.Altium.Tests/PropertyCoverage/CoverageReportTests.cs
@@ -17,8 +17,6 @@ public void GenerateCoverageReport()
         var sb = new StringBuilder();
         sb.AppendLine("# Property Coverage Report");
         sb.AppendLine();
-        sb.AppendLine($"Generated: {DateTime.UtcNow:yyyy-MM-dd HH:mm} UTC");
-        sb.AppendLine();
 
         // PCB types
         sb.AppendLine("## PCB Primitive Types");
@@ -121,10 +119,13 @@ public void GenerateCoverageReport()
             sb.AppendLine();
         }
 
-        // Write the report
+        // Write the report only when its content changed, so a plain test run
+        // leaves the working tree clean.
         var reportPath = Path.Combine(GetTestDataPath(), "..", "tests", "COVERAGE.md");
         reportPath = Path.GetFullPath(reportPath);
-        File.WriteAllText(reportPath, sb.ToString());
+        var report = sb.ToString();
+        if (!File.Exists(reportPath) || File.ReadAllText(reportPath) != report)
+            File.WriteAllText(reportPath, report);
 
         // Also output to test console
         Assert.True(true, sb.ToString());
diff --git a/tests/OriginalCircuit.Altium.Tests/RoundTrip/FileComparisonTest.cs b/tests/OriginalCircuit.Altium.Tests/RoundTrip/FileComparisonTest.cs
index fb27e22..4090b2b 100644
--- a/tests/OriginalCircuit.Altium.Tests/RoundTrip/FileComparisonTest.cs
+++ b/tests/OriginalCircuit.Altium.Tests/RoundTrip/FileComparisonTest.cs
@@ -1,6 +1,7 @@
 using System.IO.Compression;
 using System.Text;
 using OpenMcdf;
+using OriginalCircuit.Altium.Serialization.Readers;
 using Xunit;
 using Xunit.Abstractions;
 
@@ -16,24 +17,35 @@ public FileComparisonTest(ITestOutputHelper output)
     }
 
     [SkippableFact]
-    public void CompareOriginalAndWrittenPcbLib()
+    public async Task CompareOriginalAndWrittenPcbLib()
     {
         var origPath = GetDataPath("TestData", "Generated", "Individual", "PCB", "BODY_3D_STEP.PcbLib");
-        var writtenPath = GetDataPath("TestData", "Generated", "Individual", "PCB", "BODY_3D_STEP_CHECKSUM0.PcbLib");
-        if (!File.Exists(origPath) || !File.Exists(writtenPath)) { Skip.If(true, "Test data not available"); return; }
+        if (!File.Exists(origPath)) { Skip.If(true, "Test data not available"); return; }
+
+        // Regenerate the written variant in memory (zeroed model checksums, as
+        // RawDataPreservationTest saves it) instead of depending on a file on disk.
+        await using var origRead = File.OpenRead(origPath);
+        var library = new PcbLibReader().Read(origRead);
+        foreach (var model in library.Models)
+            model.Checksum = 0;
+        using var writtenMs = new MemoryStream();
+        await library.SaveAsync(writtenMs);
 
         _output.WriteLine("=== ORIGINAL ===");
         DumpCompoundFile(origPath);
 
         _output.WriteLine("\n\n=== WRITTEN ===");
-        DumpCompoundFile(writtenPath);
+        _output.WriteLine($"In-memory zero-checksum variant ({writtenMs.Length} bytes)");
+        writtenMs.Position = 0;
+        using (var writtenDump = RootStorage.Open(writtenMs, StorageModeFlags.LeaveOpen))
+            DumpStorage(writtenDump, "");
 
         // Now do a detailed byte comparison of each stream
         _output.WriteLine("\n\n=== STREAM-BY-STREAM COMPARISON ===");
         using var origFs = File.OpenRead(origPath);
         using var origCf = RootStorage.Open(origFs, StorageModeFlags.LeaveOpen);
-        using var writtenFs = File.OpenRead(writtenPath);
-        using var writtenCf = RootStorage.Open(writtenFs, StorageModeFlags.LeaveOpen);
+        writtenMs.Position = 0;
+        using var writtenCf = RootStorage.Open(writtenMs, StorageModeFlags.LeaveOpen);
 
         CompareStorage(origCf, writtenCf, "");
     }
diff --git a/tests/OriginalCircuit.Altium.Tests/RoundTrip/RawDataPreservationTest.cs b/tests/OriginalCircuit.Altium.Tests/RoundTrip/RawDataPreservationTest.cs
index 1a8881e..7e8c47f 100644
--- a/tests/OriginalCircuit.Altium.Tests/RoundTrip/RawDataPreservationTest.cs
+++ b/tests/OriginalCircuit.Altium.Tests/RoundTrip/RawDataPreservationTest.cs
@@ -30,8 +30,9 @@ public async Task PcbLib_SaveWithZeroChecksum()
             model.Checksum = 0;
         }
 
-        // Save to a new file next to the original
-        var outPath = GetDataPath("TestData", "Generated", "Individual", "PCB", "BODY_3D_STEP_CHECKSUM0.PcbLib");
+        // Save outside the repository — writing into TestData would dirty the working
+        // tree on every run (the OLE directory FILETIMEs differ between writes).
+        var outPath = Path.Combine(Path.GetTempPath(), "BODY_3D_STEP_CHECKSUM0.PcbLib");
         await library.SaveAsync(outPath, new OriginalCircuit.Eda.Models.SaveOptions());
         _output.WriteLine($"Saved to: {outPath}");
     }