am2.waitForState(RMAppAttemptState.FAILED);
rm1.waitForState(app1.getApplicationId(), RMAppState.ACCEPTED);
// restart am
MockAM am3 = MockRM.launchAM(app1, rm1, nm1);
registerResponse = am3.registerAppAttempt();
rm1.waitForState(app1.getApplicationId(), RMAppState.RUNNING);
// check am3 get the NM token from both am1 and am2;
List<NMToken> transferredTokens = registerResponse.getNMTokensFromPreviousAttempts();
Assert.assertEquals(2, transferredTokens.size());