Occasional hangs

[dkfellows]

Sometimes, tests hang during the blacklist testing. I think it's in a test that validates whether we're doing the right thing above the part where it hits the real BMP. It only happens sometimes, and isn't easy to reproduce.

Log+StackTrace: (from a failing build)

2023-09-11 14:26:36,134 INFO o.s.t.c.s.AbstractTestContextBootstrapper [main] Using TestExecutionListeners: [org.springframework.test.context.web.ServletTestExecutionListener@26f518d4, org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener@6f0e2e0f, org.springframework.test.context.event.ApplicationEventsTestExecutionListener@22f81f65, org.springframework.boot.test.mock.mockito.MockitoTestExecutionListener@92cb796, org.springframework.test.context.support.DependencyInjectionTestExecutionListener@7112ddf, org.springframework.test.context.support.DirtiesContextTestExecutionListener@19711564, org.springframework.test.context.transaction.TransactionalTestExecutionListener@7b903218, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener@17ecaafb, org.springframework.test.context.event.EventPublishingTestExecutionListener@199d120c, org.springframework.boot.test.mock.mockito.ResetMocksTestExecutionListener@856ee6e]
2023-09-11 14:26:36,251 INFO u.a.m.s.a.b.MockTransceiver [main] constructed dummy transceiver for foo_machine (/1.1.1.1 : [board=0])
2023-09-11 14:26:36,294 INFO u.a.m.s.a.b.MockTransceiver [ThreadPoolTaskScheduler-1] readBoardSerialNumber([c:0,f:0],board=0)
2023-09-11 14:26:36,296 INFO u.a.m.s.a.b.MockTransceiver [ThreadPoolTaskScheduler-1] readSerialFlash([c:0,f:0],board=0,0x00000100,256)
2023-09-11 14:26:37,849 INFO u.a.m.s.a.b.MockTransceiver [ThreadPoolTaskScheduler-1] readBoardSerialNumber([c:0,f:0],board=0)
2023-09-11 14:26:37,849 INFO u.a.m.s.a.b.MockTransceiver [ThreadPoolTaskScheduler-1] readBMPMemory([c:0,f:0],board=0,0x00001000,4096)
2023-09-11 14:26:37,851 INFO u.a.m.s.a.b.MockTransceiver [ThreadPoolTaskScheduler-1] readSerialFlash([c:0,f:0],board=0,0x00000000,256)
2023-09-11 14:26:37,851 INFO u.a.m.s.a.b.MockTransceiver [ThreadPoolTaskScheduler-1] writeFlash([c:0,f:0],board=0,0x00001000,4096)
2023-09-11 14:26:37,853 INFO u.a.m.s.a.b.MockTransceiver [ThreadPoolTaskScheduler-1] writeSerialFlash([c:0,f:0],board=0,0x00000000:512)
2023-09-11 14:26:39,411 INFO u.a.m.s.a.b.MockTransceiver [ThreadPoolTaskScheduler-1] readBoardSerialNumber([c:0,f:0],board=0)
Error:  Tests run: 3, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 18.29 s <<< FAILURE! -- in uk.ac.manchester.spinnaker.alloc.bmp.BlacklistCommsTest
Error:  uk.ac.manchester.spinnaker.alloc.bmp.BlacklistCommsTest.getSerialNumber -- Time elapsed: 15.07 s <<< ERROR!
java.util.concurrent.TimeoutException: getSerialNumber() timed out after 15 seconds
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	Suppressed: java.lang.InterruptedException
		at java.base/java.lang.Object.wait(Native Method)
		at uk.ac.manchester.spinnaker.alloc.allocator.Epochs$Epoch.getChanged(Epochs.java:253)
		at uk.ac.manchester.spinnaker.alloc.allocator.Epochs$Epoch.waitForChange(Epochs.java:237)
		at uk.ac.manchester.spinnaker.alloc.admin.MachineStateControl$Op.getResult(MachineStateControl.java:887)
		at uk.ac.manchester.spinnaker.alloc.admin.MachineStateControl$Op.completed(MachineStateControl.java:907)
		at uk.ac.manchester.spinnaker.alloc.admin.MachineStateControl.getSerialNumber(MachineStateControl.java:764)
		at uk.ac.manchester.spinnaker.alloc.bmp.BlacklistCommsTest.getSerialNumber(BlacklistCommsTest.java:131)
		at java.base/java.lang.reflect.Method.invoke(Method.java:564)
		... 2 more

I see nothing obviously wrong in that log excerpt (before the timeout).

Workaround: Rerun the test.