investigate flaky test FluxBlackboxProcessorVerification > required_spec312_cancelMustMakeThePublisherToEventuallyStopSignaling

[OlegDokuka]

see https://github.com/reactor/reactor-core/actions/runs/5110619465/jobs/9186723372?pr=3460

Gradle suite > Gradle test > reactor.core.publisher.tck.FluxBlackboxProcessorVerification > required_spec312_cancelMustMakeThePublisherToEventuallyStopSignaling FAILED
    java.lang.AssertionError: Publisher signalled [16] elements, which is more than the signalled demand: 15 expected [true] but found [false]
        at org.testng.Assert.fail(Assert.java:110)
        at org.testng.Assert.failNotEquals(Assert.java:1413)
        at org.testng.Assert.assertTrue(Assert.java:56)
        at org.reactivestreams.tck.PublisherVerification$25.run(PublisherVerification.java:978)
        at org.reactivestreams.tck.PublisherVerification.activePublisherTest(PublisherVerification.java:1135)
        at org.reactivestreams.tck.PublisherVerification.required_spec312_cancelMustMakeThePublisherToEventuallyStopSignaling(PublisherVerification.java:936)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.testng.internal.invokers.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:136)
        at org.testng.internal.invokers.TestInvoker.invokeMethod(TestInvoker.java:658)
        at org.testng.internal.invokers.TestInvoker.invokeTestMethod(TestInvoker.java:219)
        at org.testng.internal.invokers.MethodRunner.runInSequence(MethodRunner.java:50)
        at org.testng.internal.invokers.TestInvoker$MethodInvocationAgent.invoke(TestInvoker.java:923)
        at org.testng.internal.invokers.TestInvoker.invokeTestMethods(TestInvoker.java:192)
        at org.testng.internal.invokers.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:146)
        at org.testng.internal.invokers.TestMethodWorker.run(TestMethodWorker.java:128)
        at java.util.ArrayList.forEach(ArrayList.java:1259)
        at org.testng.TestRunner.privateRun(TestRunner.java:808)
        at org.testng.TestRunner.run(TestRunner.java:603)
        at org.testng.SuiteRunner.runTest(SuiteRunner.java:429)
        at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:423)
        at org.testng.SuiteRunner.privateRun(SuiteRunner.java:383)
        at org.testng.SuiteRunner.run(SuiteRunner.java:326)
        at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
        at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:95)
        at org.testng.TestNG.runSuitesSequentially(TestNG.java:1249)
        at org.testng.TestNG.runSuitesLocally(TestNG.java:1169)
        at org.testng.TestNG.runSuites(TestNG.java:1092)
        at org.testng.TestNG.run(TestNG.java:1060)
        at org.gradle.api.internal.tasks.testing.testng.TestNGTestClassProcessor.runTests(TestNGTestClassProcessor.java:146)
        at org.gradle.api.internal.tasks.testing.testng.TestNGTestClassProcessor.stop(TestNGTestClassProcessor.java:91)
        at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.stop(SuiteTestClassProcessor.java:62)
        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:498)
        at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
        at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
        at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33)
        at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:94)
        at com.sun.proxy.$Proxy2.stop(Unknown Source)
        at org.gradle.api.internal.tasks.testing.worker.TestWorker$3.run(TestWorker.java:193)
        at org.gradle.api.internal.tasks.testing.worker.TestWorker.executeAndMaintainThreadName(TestWorker.java:129)
        at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:100)
        at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:60)
        at org.gradle.process.internal.worker.child.ActionExecutionWorker.execute(ActionExecutionWorker.java:56)
        at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:113)
        at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:65)
        at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69)
        at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74)