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TestProject1/PersistenceTests.cs

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+namespace TestProject1;
+using PersistentMap;
+public class PersistenceTests
+{
+    private readonly UnicodeStrategy _strategy = new UnicodeStrategy();
+
+    [Fact]
+    public void PersistentMap_IsTrulyImmutable()
+    {
+        var v0 = BaseOrderedMap<string, int, UnicodeStrategy>.Create(_strategy);
+        var v1 = v0.Set("A", 1);
+        var v2 = v1.Set("B", 2);
+
+        // v0 should be empty
+        Assert.False(v0.ContainsKey("A"));
+        
+        // v1 should have A but not B
+        Assert.True(v1.ContainsKey("A"));
+        Assert.False(v1.ContainsKey("B"));
+
+        // v2 should have both
+        Assert.True(v2.ContainsKey("A"));
+        Assert.True(v2.ContainsKey("B"));
+    }
+
+    [Fact]
+    public void TransientToPersistent_CreatesSnapshot()
+    {
+        var tMap = BaseOrderedMap<string, int, UnicodeStrategy>.CreateTransient(_strategy);
+        tMap.Set("A", 1);
+
+        // Create Snapshot
+        var pMap = tMap.ToPersistent();
+
+        // Mutate Transient Map further
+        tMap.Set("B", 2);
+        tMap.Remove("A");
+
+        // Assert Transient State
+        Assert.False(tMap.ContainsKey("A"));
+        Assert.True(tMap.ContainsKey("B"));
+
+        // Assert Persistent Snapshot (Should be isolated)
+        Assert.True(pMap.ContainsKey("A")); // A should still be here
+        Assert.False(pMap.ContainsKey("B")); // B should not exist
+    }
+
+    [Fact]
+    public void PersistentToTransient_DoesNotCorruptSource()
+    {
+        var pMap = BaseOrderedMap<string, int, UnicodeStrategy>.Create(_strategy);
+        pMap = pMap.Set("Fixed", 1);
+
+        var tMap = pMap.ToTransient();
+        tMap.Set("Fixed", 999); // Modify shared key
+
+        // pMap should remain 1
+        Assert.True(pMap.TryGetValue("Fixed", out int val));
+        Assert.Equal(1, val);
+    }
+}