Avoid unnecessary list creation & processing in AbstractTestContextBootstrapper

Closes gh-35995

Author: sbrannen

spring-test/src/main/java/org/springframework/test/context/support/AbstractTestContextBootstrapper.java

@@ -152,7 +152,9 @@ public final List<TestExecutionListener> getTestExecutionListeners() {
 listeners.addAll(getDefaultTestExecutionListeners());
 }
 
-listeners.addAll(0, instantiateListeners(testExecutionListeners.listeners()));
+if (testExecutionListeners.listeners().length > 0) {
+listeners.addAll(0, instantiateListeners(testExecutionListeners.listeners()));
+}
 
 descriptor = (inheritListeners ? parentDescriptor : null);
 }
@@ -316,17 +318,25 @@ private MergedContextConfiguration buildMergedContextConfiguration(Class<?> test
 }
 if (contextLoader instanceof SmartContextLoader smartContextLoader) {
 smartContextLoader.processContextConfiguration(configAttributes);
-locations.addAll(0, Arrays.asList(configAttributes.getLocations()));
-classes.addAll(0, Arrays.asList(configAttributes.getClasses()));
+if (configAttributes.getLocations().length > 0) {
+locations.addAll(0, Arrays.asList(configAttributes.getLocations()));
+}
+if (configAttributes.getClasses().length > 0) {
+classes.addAll(0, Arrays.asList(configAttributes.getClasses()));
+}
 }
 else {
 @SuppressWarnings("deprecation")
 String[] processedLocations = contextLoader.processLocations(
 configAttributes.getDeclaringClass(), configAttributes.getLocations());
-locations.addAll(0, Arrays.asList(processedLocations));
+if (processedLocations.length > 0) {
+locations.addAll(0, Arrays.asList(processedLocations));
+}
 // Legacy ContextLoaders don't know how to process classes
 }
-initializers.addAll(0, Arrays.asList(configAttributes.getInitializers()));
+if (configAttributes.getInitializers().length > 0) {
+initializers.addAll(0, Arrays.asList(configAttributes.getInitializers()));
+}
 if (!configAttributes.isInheritLocations()) {
 break;
 }
@@ -401,7 +411,9 @@ private List<ContextCustomizerFactory> getContextCustomizerFactories(Class<?> te
 
 boolean inheritFactories = annotation.inheritFactories();
 AnnotationDescriptor<ContextCustomizerFactories> parentDescriptor = descriptor.next();
-factories.addAll(0, instantiateCustomizerFactories(annotation.factories()));
+if (annotation.factories().length > 0) {
+factories.addAll(0, instantiateCustomizerFactories(annotation.factories()));
+}
 
 // If there are no factories to inherit, we might need to merge the
 // locally declared factories with the defaults.