architjainjain commented on code in PR #6501: URL: https://github.com/apache/hive/pull/6501#discussion_r3718141799
########## ql/src/test/org/apache/hadoop/hive/ql/exec/tez/monitoring/yarnqueue/TestNoOpQueueMetricsCollector.java: ########## @@ -0,0 +1,147 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.hadoop.hive.ql.exec.tez.monitoring.yarnqueue; + +import org.junit.Test; + +import static org.junit.Assert.assertEquals; +import static org.junit.Assert.assertFalse; +import static org.junit.Assert.assertNotNull; +import static org.junit.Assert.assertNull; +import static org.junit.Assert.assertSame; +import static org.junit.Assert.fail; + +/** + * Test cases for NoOpQueueMetricsCollector (Null Object pattern implementation). + */ +public class TestNoOpQueueMetricsCollector { + + @Test + public void testInstanceIsSingleton() { + NoOpQueueMetricsCollector instance1 = NoOpQueueMetricsCollector.INSTANCE; + NoOpQueueMetricsCollector instance2 = NoOpQueueMetricsCollector.INSTANCE; + + assertNotNull("Instance should not be null", instance1); + assertSame("INSTANCE should return same reference", instance1, instance2); + } + + @Test + public void testIsEnabledReturnsFalse() { + NoOpQueueMetricsCollector collector = NoOpQueueMetricsCollector.INSTANCE; + + assertFalse("isEnabled should return false", collector.isEnabled()); + } + + @Test + public void testGetLatestSnapshotReturnsNull() { + NoOpQueueMetricsCollector collector = NoOpQueueMetricsCollector.INSTANCE; + + assertNull("getLatestSnapshot should return null", collector.getLatestSnapshot()); + } + + @Test + public void testGetQueueNameReturnsEmptyString() { + NoOpQueueMetricsCollector collector = NoOpQueueMetricsCollector.INSTANCE; + + String queueName = collector.getQueueName(); + assertNotNull("Queue name should not be null", queueName); + assertEquals("Queue name should be empty string", "", queueName); + } + + @Test + public void testShutdownIsNoOp() { + NoOpQueueMetricsCollector collector = NoOpQueueMetricsCollector.INSTANCE; + + // Should not throw exception + collector.shutdown(); + // Collector still usable after shutdown - confirms it is truly a no-op + assertFalse("Collector should remain disabled after shutdown", collector.isEnabled()); + assertNull("Snapshot should remain null after shutdown", collector.getLatestSnapshot()); + } + + @Test + public void testShutdownIsIdempotent() { + NoOpQueueMetricsCollector collector = NoOpQueueMetricsCollector.INSTANCE; + + // Multiple calls should all be safe no-ops + collector.shutdown(); + collector.shutdown(); + collector.shutdown(); + + // Verify instance still works after shutdown calls + assertFalse("isEnabled should still return false", collector.isEnabled()); + assertNull("getLatestSnapshot should still return null", collector.getLatestSnapshot()); + } + + + @Test + public void testNullObjectPatternAllowsSafePolymorphism() { + // NoOp collector can be used wherever QueueMetricsCollector is expected + // without null checks + NoOpQueueMetricsCollector collector = NoOpQueueMetricsCollector.INSTANCE; + + // Simulate typical usage pattern + if (collector.isEnabled()) { + // This branch should never execute + fail("NoOp collector should never report as enabled"); + } + + // Safe to call getLatestSnapshot without null check on collector + // (though snapshot itself will be null) + assertNull("Snapshot should be null", collector.getLatestSnapshot()); + + // Safe to get queue name without null check + assertNotNull("Queue name should not be null", collector.getQueueName()); + + // Safe to call shutdown without null check + collector.shutdown(); // No exception + } + + @Test + public void testCanBeUsedInPlaceOfNullCollector() { + // Common pattern: use NoOp instead of null to avoid null checks + NoOpQueueMetricsCollector collector = NoOpQueueMetricsCollector.INSTANCE; + + // This would NPE if collector was null + String queueName = collector.getQueueName(); + assertNotNull("Should not throw NPE", queueName); + + boolean enabled = collector.isEnabled(); + assertFalse("Should safely return false", enabled); + } + + @Test + public void testToStringDoesNotThrow() { + NoOpQueueMetricsCollector collector = NoOpQueueMetricsCollector.INSTANCE; + + String str = collector.toString(); + assertNotNull("toString should not return null", str); + } + + @Test + public void testHashCodeIsConsistent() { Review Comment: done -- This is an automated message from the Apache Git Service. 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