Add failing testcases for wrong order in batch save and possible fix for one of them

ebean-test/src/test/java/io/ebeaninternal/server/transaction/TransactionTest.java

@@ -0,0 +1,70 @@
+package io.ebeaninternal.server.transaction;
+
+import io.ebean.*;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.tests.model.basic.relates.*;
+
+public class TransactionTest extends BaseTestCase {
+  private Relation1 r1 = new Relation1("R1");
+  private Relation2 r2 = new Relation2("R2");
+  private Relation3 r3 = new Relation3("R3");
+
+  private Transaction txn;
+
+  @BeforeEach
+  void beginTransaction() {
+    txn = DB.beginTransaction();
+    txn.setBatchMode(true);
+  }
+
+  @AfterEach
+  void commitTransaction() {
+    txn.commit();
+    txn.close();
+  }
+
+  @Test
+  public void testMultiSave1() {
+    r2.setWithCascade(r3);
+    r1.setWithCascade(r2);
+    DB.save(r1);
+  }
+
+  @Test
+  public void testMultiSave2() {
+    r2.setWithCascade(r3);
+    r1.setWithCascade(r2);
+    DB.save(r3);
+    DB.save(r1);
+  }
+
+  @Test
+  public void testMultiSave3() {
+    r2.setWithCascade(r3);
+    r1.setWithCascade(r2);
+    DB.save(r3);
+    DB.save(r2);
+    DB.save(r1);
+  }
+
+  @Test
+  public void testMultiSave4() {
+    r2.setNoCascade(r3);
+    r1.setWithCascade(r2);
+    DB.save(r3);
+    // Workaround: txn.flush();
+    DB.save(r1);
+  }
+
+  @Test
+  public void testMultiSave5() {
+    r2.setNoCascade(r3);
+    r1.setNoCascade(r2);
+    DB.save(r3);
+    DB.save(r2);
+    DB.save(r1);
+  }
+}