Intermittently breaking test case - SimpleStepFactoryBeanTests.testSimpleConcurrentJob

[isanghaessi]

I found a test case that breaks intermittently during working on #4755.

spring-batch/spring-batch-core/src/test/java/org/springframework/batch/core/step/item/SimpleStepFactoryBeanTests.java

Lines 149 to 165 in 3bcc525

	@Test
	void testSimpleConcurrentJob() throws Exception {
	SimpleStepFactoryBean<String, String> factory = getStepFactory("foo", "bar");
	factory.setTaskExecutor(new SimpleAsyncTaskExecutor());
	AbstractStep step = (AbstractStep) factory.getObject();
	step.setName("step1");
	JobExecution jobExecution = repository.createJobExecution(job.getName(), new JobParameters());
	StepExecution stepExecution = jobExecution.createStepExecution(step.getName());
	repository.add(stepExecution);
	step.execute(stepExecution);
	assertEquals(BatchStatus.COMPLETED, stepExecution.getStatus());
	assertEquals(2, written.size());
	assertTrue(written.contains("foo"));
	}

This test case wants to test concurrent job.
But, used Collections are not thread safe.

spring-batch/spring-batch-core/src/test/java/org/springframework/batch/core/step/item/SimpleStepFactoryBeanTests.java

Lines 68 to 76 in 3bcc525

	private final List<Exception> listened = new ArrayList<>();
	private JobRepository repository;
	private final List<String> written = new ArrayList<>();
	private final ItemWriter<String> writer = data -> written.addAll(data.getItems());
	private ItemReader<String> reader = new ListItemReader<>(Arrays.asList("a", "b", "c"));

These collections should be thread safe.

[isanghaessi]

Here's my fix PR #4950. PTAL! 👋