diff --git a/server/sockeye.csproj b/server/sockeye.csproj
index a271fc9..ae93a5c 100644
--- a/server/sockeye.csproj
+++ b/server/sockeye.csproj
@@ -69,6 +69,8 @@
     </Content>  
   </ItemGroup>
    
-
+  <ItemGroup>
+    <InternalsVisibleTo Include="sockeye.tests" />
+  </ItemGroup>
 
 </Project>
\ No newline at end of file
diff --git a/sockeye.tests/ResignTests.cs b/sockeye.tests/ResignTests.cs
new file mode 100644
index 0000000..983b0eb
--- /dev/null
+++ b/sockeye.tests/ResignTests.cs
@@ -0,0 +1,102 @@
+namespace sockeye.tests;
+
+/*
+Extract key fixture data, note that pgroup / format is 1 for v7 product family keys and not 1 for any v8 family keys
+mkdir C:\data\sockeye-fixtures
+$env:PGCLIENTENCODING = "UTF8"
+.\psql -U postgres -d sockeye -At -o C:\data\sockeye-fixtures\resign.json -c "
+  SELECT json_agg(t ORDER BY t.id) FROM (
+    SELECT id,
+           pgroup AS format,
+           key
+    FROM alicense
+    WHERE key IS NOT NULL
+  ) t;"
+
+
+
+*/
+// public class UnitTest1
+// {
+//     [Fact]
+//     public void Test1()
+//     {
+
+//     }
+// }
+
+
+using System.Text.Json;
+
+public record ResignRow(long Id, int Format, string Key);
+
+public static class ResignFixture
+{
+    static readonly Lazy<Dictionary<long, ResignRow>> _rows = new(Load);
+    public static IReadOnlyDictionary<long, ResignRow> Rows => _rows.Value;
+
+    static Dictionary<long, ResignRow> Load()
+    {
+        var path = "C:\\data\\sockeye-fixtures\\resign.json";//Environment.GetEnvironmentVariable("SOCKEYE_RESIGN_FIXTURE");
+        if (string.IsNullOrWhiteSpace(path) || !File.Exists(path))
+            throw new InvalidOperationException(
+                "Set SOCKEYE_RESIGN_FIXTURE to the exported alicense JSON file.");
+
+        var rows = JsonSerializer.Deserialize<List<ResignRow>>(
+            File.ReadAllText(path),
+            new JsonSerializerOptions { PropertyNameCaseInsensitive = true });
+
+        return rows.ToDictionary(r => r.Id);
+    }
+}
+
+public class ResignTests
+{
+    public static IEnumerable<object[]> RowIds() =>
+        ResignFixture.Rows.Keys.Select(id => new object[] { id });
+
+    [Theory]
+    [MemberData(nameof(RowIds))]
+    public void Stored_licence_resigns_identically(long id)
+    {
+        var row = ResignFixture.Rows[id];
+        var keyText = Between(row.Key, "[KEY", "KEY]");
+        var expected = StripWs(Between(row.Key, "[SIGNATURE", "SIGNATURE]"));
+
+        var actual = row.Format == 1
+            ? Sockeye.Biz.KeyFactory.Sign(keyText)     // your extracted internal methods
+            : Sockeye.Biz.RavenKeyFactory.Sign(keyText);
+        //test sign returns whole key with signature need to re-extract signature only
+        actual = StripWs(Between(actual, "[SIGNATURE", "SIGNATURE]"));
+
+        Assert.Equal(expected, actual);
+    }
+
+    [Fact]
+    public void Fixture_covers_both_formats()
+    {
+        Assert.Contains(ResignFixture.Rows.Values, r => r.Format == 1);
+        Assert.Contains(ResignFixture.Rows.Values, r => r.Format == 2);
+        Assert.Contains(ResignFixture.Rows.Values, r => r.Format == 3);
+    }
+
+    [Fact]
+    public void Tampered_payload_does_not_match()
+    {
+        var row = ResignFixture.Rows.Values.First(r => r.Format == 1);
+        var keyText = Between(row.Key, "[KEY", "KEY]") + "x";
+        var expected = StripWs(Between(row.Key, "[SIGNATURE", "SIGNATURE]"));
+        Assert.NotEqual(expected, StripWs(Between(Sockeye.Biz.KeyFactory.Sign(keyText), "[SIGNATURE", "SIGNATURE]")));
+    }
+
+    static string Between(string s, string start, string end)
+    {
+        int a = s.IndexOf(start, StringComparison.Ordinal);
+        int b = s.IndexOf(end, StringComparison.Ordinal);
+        if (a < 0 || b < 0 || b < a)
+            throw new FormatException($"Markers {start}/{end} not found");
+        return s.Substring(a + start.Length, b - a - start.Length);
+    }
+
+    static string StripWs(string s) => string.Concat(s.Where(c => !char.IsWhiteSpace(c)));
+}
\ No newline at end of file
diff --git a/sockeye.tests/sockeye.tests.csproj b/sockeye.tests/sockeye.tests.csproj
new file mode 100644
index 0000000..e84c3e3
--- /dev/null
+++ b/sockeye.tests/sockeye.tests.csproj
@@ -0,0 +1,21 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net6.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>disable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.11.1" />
+    <PackageReference Include="xunit" Version="2.9.2" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2" />
+  </ItemGroup>
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\server\sockeye.csproj" />
+  </ItemGroup>
+</Project>
\ No newline at end of file