Why is junit timeout annotation not working? Tests hang instead - junit

Question

I've noticed several junit tests hanging, where I would have expected them to fail via the junit timeout mechanism.
For example:
public static final long TIMEOUT = 20_000L;
#Test(timeout = TIMEOUT)
...
When the maven build occurs (surefire 2.19), I see tests occasionally hang (forever, until I abort the build...) that I would have thought junit would enforce the timeout for and fail the test, and move on.
I was able to get a threaddump of where it seems stuck. Any ideas?
"main" #1 prio=5 os_prio=0 tid=0x00007f1e18008800 nid=0x2e6 runnable [0x00007f1e201ab000]
java.lang.Thread.State: RUNNABLE
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
at java.net.SocketInputStream.read(SocketInputStream.java:170)
at java.net.SocketInputStream.read(SocketInputStream.java:141)
at org.postgresql.core.VisibleBufferedInputStream.readMore(VisibleBufferedInputStream.java:143)
at org.postgresql.core.VisibleBufferedInputStream.ensureBytes(VisibleBufferedInputStream.java:112)
at org.postgresql.core.VisibleBufferedInputStream.read(VisibleBufferedInputStream.java:70)
at org.postgresql.core.PGStream.ReceiveChar(PGStream.java:283)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1799)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:200)
- locked <0x00000000e6a9fc80> (a org.postgresql.core.v3.QueryExecutorImpl)
at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:424)
...
at org.flywaydb.core.Flyway.migrate(Flyway.java:917)
at obfuscated.before(obfuscated.java:109)
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:497)
at io.vertx.ext.unit.junit.VertxUnitRunner.invokeTestMethod(VertxUnitRunner.java:93)
at io.vertx.ext.unit.junit.VertxUnitRunner.lambda$invokeExplosively$0(VertxUnitRunner.java:114)
at io.vertx.ext.unit.junit.VertxUnitRunner$$Lambda$1/1447689627.handle(Unknown Source)
at io.vertx.ext.unit.impl.TestContextImpl$Step.run(TestContextImpl.java:128)
at io.vertx.ext.unit.impl.TestContextImpl$Step.access$200(TestContextImpl.java:30)
at io.vertx.ext.unit.impl.TestContextImpl.run(TestContextImpl.java:237)
at io.vertx.ext.unit.junit.VertxUnitRunner.invokeExplosively(VertxUnitRunner.java:130)
at io.vertx.ext.unit.junit.VertxUnitRunner.access$000(VertxUnitRunner.java:39)
at io.vertx.ext.unit.junit.VertxUnitRunner$2.evaluate(VertxUnitRunner.java:194)
at io.vertx.ext.unit.junit.VertxUnitRunner$3.evaluate(VertxUnitRunner.java:211)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
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 io.vertx.ext.unit.junit.VertxUnitRunner$2.evaluate(VertxUnitRunner.java:196)
at io.vertx.ext.unit.junit.VertxUnitRunner$3.evaluate(VertxUnitRunner.java:211)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:344)
at org.apache.maven.surefire.junit4.JUnit4Provider.executeWithRerun(JUnit4Provider.java:269)
at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:240)
at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:184)
at org.apache.maven.surefire.booter.ForkedBooter.invokeProviderInSameClassLoader(ForkedBooter.java:286)
at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:240)
at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:121)