UnknownServiceException when running 2 test methods at the same time

I have a unit test extending from AbstractTransactionalTestNGSpringContextTests which uses an inner class to define the Spring context to use. The unit test has several test methods. When I run them one by one from IntelliJ, everything is ok. However, if I run the whole class, only the first test is ok and the others fail with:

org.springframework.transaction.CannotCreateTransactionException: Could not open JPA EntityManager for transaction; nested exception is org.hibernate.service.UnknownServiceException: Unknown service requested [org.hibernate.service.jdbc.connections.spi.ConnectionProvider]
    at org.springframework.orm.jpa.JpaTransactionManager.doBegin(JpaTransactionManager.java:431)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:373)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:439)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:262)
    at org.springframework.transaction.aspectj.AbstractTransactionAspect.ajc$around$org_springframework_transaction_aspectj_AbstractTransactionAspect$1$2a73e96c(AbstractTransactionAspect.aj:64)
    at com.traficon.tmsng.server.common.detector.matrix.DetectorRelationsServiceImplIntegrationTest.reset(DetectorRelationsServiceImplIntegrationTest.java:78)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:84)
    at org.testng.internal.Invoker.invokeConfigurationMethod(Invoker.java:564)
    at org.testng.internal.Invoker.invokeConfigurations(Invoker.java:213)
    at org.testng.internal.Invoker.invokeMethod(Invoker.java:653)
    at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:901)
    at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1231)
    at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:127)
    at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:111)
    at org.testng.TestRunner.privateRun(TestRunner.java:767)
    at org.testng.TestRunner.run(TestRunner.java:617)
    at org.testng.SuiteRunner.runTest(SuiteRunner.java:348)
    at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:343)
    at org.testng.SuiteRunner.privateRun(SuiteRunner.java:305)
    at org.testng.SuiteRunner.run(SuiteRunner.java:254)
    at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
    at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
    at org.testng.TestNG.runSuitesSequentially(TestNG.java:1224)
    at org.testng.TestNG.runSuitesLocally(TestNG.java:1149)
    at org.testng.TestNG.run(TestNG.java:1057)
    at org.testng.remote.RemoteTestNG.run(RemoteTestNG.java:111)
    at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:204)
    at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:175)
    at org.testng.RemoteTestNGStarter.main(RemoteTestNGStarter.java:125)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)
Caused by: org.hibernate.service.UnknownServiceException: Unknown service requested [org.hibernate.service.jdbc.connections.spi.ConnectionProvider]
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:151)
    at org.hibernate.internal.AbstractSessionImpl.getJdbcConnectionAccess(AbstractSessionImpl.java:262)
    at org.hibernate.engine.jdbc.internal.JdbcCoordinatorImpl.<init>(JdbcCoordinatorImpl.java:106)
    at org.hibernate.engine.transaction.internal.TransactionCoordinatorImpl.<init>(TransactionCoordinatorImpl.java:90)
    at org.hibernate.internal.SessionImpl.<init>(SessionImpl.java:254)
    at org.hibernate.internal.SessionFactoryImpl$SessionBuilderImpl.openSession(SessionFactoryImpl.java:1618)
    at org.hibernate.ejb.EntityManagerImpl.getRawSession(EntityManagerImpl.java:121)
    at org.hibernate.ejb.EntityManagerImpl.getSession(EntityManagerImpl.java:97)
    at org.hibernate.ejb.AbstractEntityManagerImpl.setDefaultProperties(AbstractEntityManagerImpl.java:273)
    at org.hibernate.ejb.AbstractEntityManagerImpl.postInit(AbstractEntityManagerImpl.java:181)
    at org.hibernate.ejb.EntityManagerImpl.<init>(EntityManagerImpl.java:89)
    at org.hibernate.ejb.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:193)
    at org.hibernate.ejb.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:188)
    at org.springframework.orm.jpa.JpaTransactionManager.createEntityManagerForTransaction(JpaTransactionManager.java:449)
    at org.springframework.orm.jpa.JpaTransactionManager.doBegin(JpaTransactionManager.java:369)
    ... 37 more

Any idea why this is?

I am using Spring 4.1.3.

I tried annotating my test class with:

@DirtiesContext(classMode = DirtiesContext.ClassMode.AFTER_EACH_TEST_METHOD)

But that does not seem to change anything.