added migration generation

src/test/java/jef/model/ModelBuilderSimpleTest.java

@@ -0,0 +1,43 @@
+package jef.model;
+
+import jef.DbSet;
+import jef.model.annotations.Clazz;
+import jef.model.annotations.Id;
+import jef.model.annotations.Index;
+import jef.model.annotations.Key;
+import jef.model.annotations.Unique;
+import jef.serializable.SerializableObject;
+import lombok.Getter;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class ModelBuilderSimpleTest {
+    @Test
+    public void testClone() {
+        var mb = ModelBuilder.from(Ctx.class);
+
+        assertEquals(1, mb.getEntities().size());
+        assertEquals("objects1", mb.getEntity(TestClass.class).getName());
+        assertTrue(mb.getEntity(TestClass.class).getFields().stream().allMatch(e -> e.getEntity() == mb.getEntity(TestClass.class)));
+    }
+
+    public static class Ctx extends DbContext {
+        @Clazz(clazz = TestClass.class)
+        private DbSet<TestClass> objects1;
+    }
+
+    @Getter
+    public static class TestClass extends SerializableObject {
+        @Id
+        public int i = 1;
+        public Object o = new Object();
+        public double d;
+        public float f;
+        public long l;
+    }
+
+}