tests/Db.Tests/DomainStaysPlainTests.cs

@@ -0,0 +1,30 @@
+using Domain;
+using System.Reflection;
+
+namespace Db.Tests;
+
+/// <summary>The domain stayed clean: Client/Order do NOT derive from <see cref="DbBase"/> and expose no <see cref="DbContext"/>-typed member; asserted from the persistence side, where both are visible.</summary>
+public class DomainStaysPlainTests
+{
+    private const BindingFlags AllMembers =
+        BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Static;
+
+    // The leak is gone: no DbBase in the base chain, no DbContext-typed member (reflection).
+    [Theory]
+    [InlineData(typeof(Client))]
+    [InlineData(typeof(Order))]
+    public void Domain_objects_are_plain__no_DbBase_no_DbContext_member(Type type)
+    {
+        // Not DbBase, and not a derived type either (walk the base chain):
+        for (var t = type; t is not null && t != typeof(object); t = t.BaseType)
+            Assert.NotSame(typeof(DbBase), t);
+
+        // No DbContext-typed member, public or private:
+        foreach (var p in type.GetProperties(AllMembers))
+            Assert.True(p.PropertyType != typeof(DbContext),
+                $"{type.Name}.{p.Name} leaks a DbContext-typed property");
+        foreach (var f in type.GetFields(AllMembers))
+            Assert.True(f.FieldType != typeof(DbContext),
+                $"{type.Name}.{f.Name} leaks a DbContext-typed field");
+    }
+}