Check available processors in ParallelApplicationEventsIntegrationTests

This commit changes the condition in the if-block to check the number of
available processors instead of currently active threads with the hope
that doing so will prove more reliable on the CI server.

Author: sbrannen

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/event/ParallelApplicationEventsIntegrationTests.java

@@ -76,8 +76,9 @@ void executeTestsInParallel(Class<?> testClass) {
 		assertThat(payloads).hasSize(10);
 		assertThat(testNames).hasSize(10);
 
-		// Skip the following assertion entirely if the thread count is too low.
-		if (ManagementFactory.getThreadMXBean().getThreadCount() >= 4) {
+		// Skip the following assertion entirely if too few processors are available
+		// to the current JVM.
+		if (Runtime.getRuntime().availableProcessors() >= 4) {
 			// There are probably 10 different thread names on a developer's machine,
 			// but we really just want to assert that at least two different threads
 			// were used, since the CI server often has fewer threads available.