Hello,
since a few days a build clean / install shows problems with this test in my environment.
Example for H2 as database:
Tests run: 1, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 0.086 sec <<< FAILURE! - in org.camunda.bpm.engine.test.concurrency.DbDeadlockTest
testTransactionIsolation(org.camunda.bpm.engine.test.concurrency.DbDeadlockTest) Time elapsed: 0.085 sec <<< FAILURE!
junit.framework.AssertionFailedError: Unexpected interruption
   at junit.framework.Assert.fail(Assert.java:57)
   at junit.framework.TestCase.fail(TestCase.java:227)
   at org.camunda.bpm.engine.test.concurrency.ConcurrencyTestCase$ThreadControl.join(ConcurrencyTestCase.java:129)
   at org.camunda.bpm.engine.test.concurrency.ConcurrencyTestCase$ThreadControl.waitUntilDone(ConcurrencyTestCase.java:121)
   at org.camunda.bpm.engine.test.concurrency.DbDeadlockTest.tearDown(DbDeadlockTest.java:112)
   at junit.framework.TestCase.runBare(TestCase.java:146)
   at org.camunda.bpm.engine.impl.test.AbstractProcessEngineTestCase.runBare(AbstractProcessEngineTestCase.java:110)
   at junit.framework.TestResult$1.protect(TestResult.java:122)
   at junit.framework.TestResult.runProtected(TestResult.java:142)
   at junit.framework.TestResult.run(TestResult.java:125)
   at junit.framework.TestCase.run(TestCase.java:129)
   at junit.framework.TestSuite.runTest(TestSuite.java:255)
   at junit.framework.TestSuite.run(TestSuite.java:250)
   at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:84)
   at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:264)
   at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:153)
   at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:124)
   at org.apache.maven.surefire.booter.ForkedBooter.invokeProviderInSameClassLoader(ForkedBooter.java:200)
   at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:153)
   at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:103)
Same for oracle-12:
Tests run: 1, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 0.301 sec <<< FAILURE! - in org.camunda.bpm.engine.test.concurrency.DbDeadlockTest
testTransactionIsolation(org.camunda.bpm.engine.test.concurrency.DbDeadlockTest) Time elapsed: 0.301 sec <<< FAILURE!
junit.framework.AssertionFailedError: Unexpected interruption
   at junit.framework.Assert.fail(Assert.java:57)
   at junit.framework.TestCase.fail(TestCase.java:227)
   at org.camunda.bpm.engine.test.concurrency.ConcurrencyTestCase$ThreadControl.join(ConcurrencyTestCase.java:129)
   at org.camunda.bpm.engine.test.concurrency.ConcurrencyTestCase$ThreadControl.waitUntilDone(ConcurrencyTestCase.java:121)
   at org.camunda.bpm.engine.test.concurrency.DbDeadlockTest.tearDown(DbDeadlockTest.java:112)
   at junit.framework.TestCase.runBare(TestCase.java:146)
   at org.camunda.bpm.engine.impl.test.AbstractProcessEngineTestCase.runBare(AbstractProcessEngineTestCase.java:110)
   at junit.framework.TestResult$1.protect(TestResult.java:122)
   at junit.framework.TestResult.runProtected(TestResult.java:142)
   at junit.framework.TestResult.run(TestResult.java:125)
   at junit.framework.TestCase.run(TestCase.java:129)
   at junit.framework.TestSuite.runTest(TestSuite.java:255)
   at junit.framework.TestSuite.run(TestSuite.java:250)
   at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:84)
   at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:264)
   at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:153)
   at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:124)
   at org.apache.maven.surefire.booter.ForkedBooter.invokeProviderInSameClassLoader(ForkedBooter.java:200)
   at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:153)
   at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:103)
Using my patched version with IBM informix as database this test just hangs, one session waiting for the other one because of locks.
No deadlock. Waiting endless possibly because lock timeout is configured as infinite.
You do not see this problem during your test runs? The class it self not really changed, anything in the underlying classes?
Command for H2: mvn install -Pdistro-serverless -Pdistro-wildfly9
Oracle: mvn install -Pdistro-serverless -Pdistro-wildfly9 -Pdatabase,oracle-12 -Ddatabase.username="..." -Ddatabase.password="..." -Ddatabase.driver="oracle.jdbc.OracleDriver" -Ddatabase.url="jdbc:oracle:thin:@sb2000:1521:DEV"
Regards, Frank