Spring Integration file adapter tests failing on macOS - spring-integration

Question

I have a spring integration project with multiple tests that runs perfectly fine on Windows and Linux machines. Now, I've just bought a MacBook and tried running the tests on it. All of my file adapter tests (15) are failing.
The below example test verifies that when a file is placed in the inboundOutDirectory directory, that it's properly processed.
Test class example:
#RunWith(SpringRunner.class)
#ContextConfiguration(
initializers = ConfigFileApplicationContextInitializer.class,
classes = {StructuralEnricherIntegrationFlow.class, StructuralEnricherIntegrationFlowTests.Config.class})
#SpringIntegrationTest
#DirtiesContext
public class StructuralEnricherIntegrationFlowTests {
#Autowired
private MockIntegrationContext mockIntegrationContext;
#Autowired
private File inboundOutDirectory;
#Autowired
private File inboundProcessedDirectory;
#Autowired
private File inboundFailedDirectory;
#Autowired
private PollableChannel testChannel;
#After
public void tearDown() throws IOException {
FileUtils.cleanDirectory(inboundOutDirectory);
FileUtils.cleanDirectory(inboundProcessedDirectory);
FileUtils.cleanDirectory(inboundFailedDirectory);
}
#Test
public void testStructuralEnricherFlowEmptyResponse() throws Exception {
// given
String docId = "xxx";
// when
MessageHandler mockMessageHandler = mockMessageHandler().handleNextAndReply(m -> "{}");
this.mockIntegrationContext.substituteMessageHandlerFor("structuralEnricherEndpoint", mockMessageHandler);
String fileName = TestingUtils.createFileAggregated(docId, 1, ".json", inboundOutDirectory,
"{}");
// then
Message<String> receive = (Message<String>) testChannel.receive(3000);
JSONAssert.assertEquals(String.format("{xxx"),
receive.getPayload(), JSONCompareMode.LENIENT);
assertTrue(FileUtils.getFile(new File(this.inboundProcessedDirectory, fileName)).exists());
}
#Configuration
#EnableIntegration
public static class Config {
#Autowired
private File inboundOutDirectory;
#Bean
public PollableChannel testChannel() {
return new QueueChannel();
}
#Bean
public IntegrationFlow processedDirectory(#Value("${pattern}") String pattern) {
return IntegrationFlows
.from(Files.inboundAdapter(inboundOutDirectory)
.regexFilter(pattern)
.useWatchService(true)
.watchEvents(FileReadingMessageSource.WatchEventType.CREATE),
e -> e.poller(Pollers.fixedDelay(100)))
.transform(Files.toStringTransformer())
.channel("testChannel")
.get();
}
}
}
It seems that the testChannel never receives a message as I'm getting a NullPointerException at receive.getPayload(). I've tried increasing the timeout but it didn't help.
System info:
spring-boot-starter-parent 2.3.4.RELEASE
MacBook Pro 13 (2020) with macOS Big Sur 11.1
openjdk version "1.8.0_275"
The same test works for example on ubuntu with java version 1.8.0_275.
I'm not sure what's the problem so hopefully, you can help me out.
UPDATE
So it seems that the problem lies in the useWatchService(true) in the Files.inboundAdapter. This is how the processing of the document is currently triggered:
return IntegrationFlows
.from(Files.inboundAdapter(inboundOutDirectory)
.regexFilter(intermediatePattern)
.useWatchService(true)
.watchEvents(FileReadingMessageSource.WatchEventType.CREATE,
FileReadingMessageSource.WatchEventType.DELETE),
e -> e.poller(Pollers.fixedDelay(1000)
.taskExecutor(Executors.newFixedThreadPool(2))
.maxMessagesPerPoll(5)))
I have debugged this flow a bit more and it appears that when .useWatchService(true), then the adapter will pick up the file with a delay (it takes about 10 seconds). Not sure why it works differently on macOS. When I change it to .useWatchService(false), it works instantly.
Here is the util method that creates the files:
public static String createFileAggregated(String id, Integer documentId, String extension, File tmpDir, String content) throws Exception {
String filename = String.format("%s%04d%s", id, documentId, extension);
FileUtils.write(new File(tmpDir, filename), (Optional.ofNullable(content).orElse(filename)), "UTF-8", false);
return filename;
}