java单元测试@Transactional无法提交JPA事务；标记为仅回滚的事务

Question

我正在为我的Spring应用程序编写JUnit测试。对于其中一种情况，我得到了一个例外

Could not commit JPA transaction; nested exception is javax.persistence.RollbackException: Transaction marked as rollbackOnly.

我读了其他一些问题和答案，但它们没有帮助。我遇到问题的情况很简单。我想检查实体字段的唯一约束是否被强制执行。我创建了两个具有相同字段的实体，并期望出现约束冲突异常。调用方法被标记为@Transactional，因为如果发生异常，我希望整个过程回滚

代码如下：

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = DeadlinesApplication.class)
@Rollback(value = false)
public class UserHelperTest {
    @Autowired
    private UserHelper userHelper;

    @Test(expected = DataIntegrityViolationException.class)
    @Transactional
    public void uniqueUsername() throws NullParameterException {
        User user = userHelper.createUser("uniq1", "password", null, null);
        User user2 = userHelper.createUser("uniq2", "password", null, null);
        User user3 = userHelper.createUser("uniq2", "password", null, null);
    }

UserHelper类被称为：

@Service
public class UserHelper {
    @Autowired
    private UserDAO userDAO;


    public User createUser(...) throws NullParameterException {
        User newUser = new User(username, ...);

        userDAO.save(newUser);

        return newUser;
    }

UserDAO的save()方法随后在UserRepository上调用save()：

@Repository
public interface UserRepository extends CrudRepository<User, Long> {
    public User findByUsername(String username);
}

唯一有@Transactional的地方是测试方法。它必须存在，因为在一个单独的测试方法中，我懒得加载多对多关系，而这需要在一个事务中发生

你能看到这个代码有什么问题吗

编辑：stacktrace错误

org.springframework.transaction.TransactionSystemException: Could not commit JPA transaction; nested exception is javax.persistence.RollbackException: Transaction marked as rollbackOnly

    at org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:526)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:761)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:730)
    at org.springframework.test.context.transaction.TransactionContext.endTransaction(TransactionContext.java:128)
    at org.springframework.test.context.transaction.TransactionalTestExecutionListener.afterTestMethod(TransactionalTestExecutionListener.java:224)
    at org.springframework.test.context.TestContextManager.afterTestMethod(TestContextManager.java:313)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:94)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:254)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:89)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:193)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:119)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
Caused by: javax.persistence.RollbackException: Transaction marked as rollbackOnly
    at org.hibernate.jpa.internal.TransactionImpl.commit(TransactionImpl.java:74)
    at org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:517)
    ... 29 more

2016-03-26 20:53:52.913  INFO 2448 --- [       Thread-3] s.c.a.AnnotationConfigApplicationContext : Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@20deea7f: startup date [Sat Mar 26 20:53:44 CET 2016]; root of context hierarchy
2016-03-26 20:53:52.924  INFO 2448 --- [       Thread-3] j.LocalContainerEntityManagerFactoryBean : Closing JPA EntityManagerFactory for persistence unit 'default'