fix: Using the same seed for idempotent guid returns the same sequence of guids instead of changing based off of the entity type

Author: thiagomvas

src/FluentSeeding/Idempotency/Idempotent.cs

@@ -39,7 +39,9 @@ public static Guid Guid<T>(int index, string? seed = null) =>
     /// <returns>A stable UUID v5 GUID uniquely identifying this type/index/seed combination.</returns>
     public static Guid Guid(Type entityType, int index, string? seed = null)
     {
-        var key = $"{entityType.Name}:{seed ?? entityType.Name}:{index}";
+        var key = seed != null
+            ? $"{seed}:{index}"
+            : $"{entityType.Name}:{index}";
         return V5Uuid(Namespace, key);
     }
 

tests/FluentSeeding.Tests/Idempotency/IdempotentGuidTests.cs

@@ -41,6 +41,28 @@ public void Guid_WhenCalledWithDifferentSeed_ReturnsDifferentValue()
         withDefaultSeed.Should().NotBe(withCustomSeed);
     }
 
+    [Test]
+    public void Guid_WhenCalledWithSameSeedAndDifferentTypes_ReturnsSameValue()
+    {
+        // Arrange / Act
+        var user = Idempotent.Guid<User>(0, "shared-seed");
+        var product = Idempotent.Guid<Product>(0, "shared-seed");
+
+        // Assert
+        user.Should().Be(product);
+    }
+
+    [Test]
+    public void Guid_WhenCalledWithNoSeedAndDifferentTypes_ReturnsDifferentValue()
+    {
+        // Arrange / Act
+        var user = Idempotent.Guid<User>(0);
+        var product = Idempotent.Guid<Product>(0);
+
+        // Assert
+        user.Should().NotBe(product);
+    }
+
     [Test]
     public void Guid_WhenCalledWithNullSeed_BehavesSameAsOmittingSeed()
     {