org.apache.beam.sdk.transforms.CombineTest$WindowingTests.testWindowedCombineGloballyAsSingletonView flaky on Dataflow Runner V2

[damccorm]

Per https://ci-beam.apache.org/job/beam_PostCommit_Java_VR_Dataflow_V2_Streaming/lastCompletedBuild/testReport/junit/org.apache.beam.sdk.transforms/CombineTest$WindowingTests/testWindowedCombineGloballyAsSingletonView/history/ this test flakes quite often.

java.lang.RuntimeException: generic::unknown: org.apache.beam.sdk.util.UserCodeException: java.lang.AssertionError:
OutputSideInput/ParMultiDo(Anonymous).output: 
Expected: iterable with items [<0>] in any order
 
   but: no item matches: <0> in []
	at org.apache.beam.sdk.util.UserCodeException.wrap(UserCodeException.java:39)
	at
org.apache.beam.sdk.testing.PAssert$DefaultConcludeFn$DoFnInvoker.invokeProcessElement(Unknown Source)
	at
org.apache.beam.fn.harness.FnApiDoFnRunner.processElementForParDo(FnApiDoFnRunner.java:758)
	at org.apache.beam.fn.harness.data.PCollectionConsumerRegistry$MetricTrackingFnDataReceiver.accept(PCollectionConsumerRegistry.java:257)
	at
org.apache.beam.fn.harness.data.PCollectionConsumerRegistry$MetricTrackingFnDataReceiver.accept(PCollectionConsumerRegistry.java:209)
	at
org.apache.beam.fn.harness.FnApiDoFnRunner.outputTo(FnApiDoFnRunner.java:1745)
	at org.apache.beam.fn.harness.FnApiDoFnRunner.access$2700(FnApiDoFnRunner.java:142)
	at
org.apache.beam.fn.harness.FnApiDoFnRunner$NonWindowObservingProcessBundleContext.outputWithTimestamp(FnApiDoFnRunner.java:2263)
	at
org.apache.beam.fn.harness.FnApiDoFnRunner$ProcessBundleContextBase.output(FnApiDoFnRunner.java:2432)
	at
org.apache.beam.sdk.testing.PAssert$GroupedValuesCheckerDoFn.processElement(PAssert.java:1541)
	at
org.apache.beam.sdk.testing.PAssert$GroupedValuesCheckerDoFn$DoFnInvoker.invokeProcessElement(Unknown
Source)
	at org.apache.beam.fn.harness.FnApiDoFnRunner.processElementForParDo(FnApiDoFnRunner.java:758)
	at
org.apache.beam.fn.harness.data.PCollectionConsumerRegistry$MetricTrackingFnDataReceiver.accept(PCollectionConsumerRegistry.java:257)
	at
org.apache.beam.fn.harness.data.PCollectionConsumerRegistry$MetricTrackingFnDataReceiver.accept(PCollectionConsumerRegistry.java:209)
	at
org.apache.beam.fn.harness.FnApiDoFnRunner.outputTo(FnApiDoFnRunner.java:1745)
	at org.apache.beam.fn.harness.FnApiDoFnRunner.access$2700(FnApiDoFnRunner.java:142)
	at
org.apache.beam.fn.harness.FnApiDoFnRunner$NonWindowObservingProcessBundleContext.outputWithTimestamp(FnApiDoFnRunner.java:2263)
	at
org.apache.beam.fn.harness.FnApiDoFnRunner$ProcessBundleContextBase.output(FnApiDoFnRunner.java:2432)
	at
org.apache.beam.sdk.transforms.DoFnOutputReceivers$WindowedContextOutputReceiver.output(DoFnOutputReceivers.java:78)
	at
org.apache.beam.sdk.transforms.MapElements$1.processElement(MapElements.java:142)
	at org.apache.beam.sdk.transforms.MapElements$1$DoFnInvoker.invokeProcessElement(Unknown
Source)
	at org.apache.beam.fn.harness.FnApiDoFnRunner.processElementForParDo(FnApiDoFnRunner.java:758)
	at
org.apache.beam.fn.harness.data.PCollectionConsumerRegistry$MetricTrackingFnDataReceiver.accept(PCollectionConsumerRegistry.java:257)
	at
org.apache.beam.fn.harness.data.PCollectionConsumerRegistry$MetricTrackingFnDataReceiver.accept(PCollectionConsumerRegistry.java:209)

Imported from Jira BEAM-13237. Original Jira may contain additional context.
Reported by: bhulette.

[kileys]

Can't repro and no in recent test failures