fix: record left status in jenkins.queue.count metric and add queue metrics test

src/main/java/io/jenkins/plugins/opentelemetry/queue/MonitoringQueueListener.java

@@ -7,7 +7,6 @@
 
 import static io.jenkins.plugins.opentelemetry.semconv.ExtendedJenkinsAttributes.STATUS;
 import static io.jenkins.plugins.opentelemetry.semconv.JenkinsMetrics.*;
-import static io.jenkins.plugins.opentelemetry.semconv.JenkinsMetrics.JENKINS_QUEUE_COUNT;
 
 import hudson.Extension;
 import hudson.model.Queue;
@@ -124,6 +123,7 @@ public void postConstruct() {
                         queueItems.record(buildable.get(), Attributes.of(STATUS, "buildable"));
                         queueBuildableItems.record(buildable.get());
                         queueItems.record(stuck.get(), Attributes.of(STATUS, "stuck"));
+                        queueItems.record(left.get(), Attributes.of(STATUS, "left"));
                         if (unknown.get() > 0) {
                             queueItems.record(unknown.get(), Attributes.of(STATUS, "unknown"));
                         }

src/test/java/io/jenkins/plugins/opentelemetry/MonitoringQueueListenerTest.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright The Original Author or Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package io.jenkins.plugins.opentelemetry;
+
+import static org.hamcrest.CoreMatchers.notNullValue;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.greaterThanOrEqualTo;
+
+import io.jenkins.plugins.opentelemetry.semconv.JenkinsMetrics;
+import io.opentelemetry.sdk.metrics.data.MetricData;
+import io.opentelemetry.sdk.testing.exporter.InMemoryMetricExporterProvider;
+import io.opentelemetry.sdk.testing.exporter.InMemoryMetricExporterUtils;
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
+import org.jenkinsci.plugins.workflow.cps.CpsFlowDefinition;
+import org.jenkinsci.plugins.workflow.job.WorkflowJob;
+import org.junit.jupiter.api.Test;
+import org.jvnet.hudson.test.junit.jupiter.WithJenkins;
+
+@WithJenkins
+public class MonitoringQueueListenerTest extends BaseIntegrationTest {
+
+    @Test
+    public void testQueueMetricsAreRegisteredAndExported() throws Exception {
+        // Use a Pipeline job — the primary supported job type for this plugin
+        WorkflowJob project = jenkinsRule.createProject(WorkflowJob.class, "queue-metrics-test");
+        project.setDefinition(new CpsFlowDefinition("node() { echo 'queue-metrics-test' }", true));
+        jenkinsRule.buildAndAssertSuccess(project);
+        jenkinsRule.waitUntilNoActivity();
+
+        // Force flush using the same pattern as BaseIntegrationTest line 246
+        jenkinsControllerOpenTelemetry
+                .getOpenTelemetrySdk()
+                .getSdkMeterProvider()
+                .forceFlush()
+                .join(10, TimeUnit.SECONDS);
+
+        // Get exported metrics using the same pattern as JenkinsOpenTelemetryPluginConfigurationIntegrationTest
+        Map<String, MetricData> exportedMetrics = InMemoryMetricExporterUtils.getLastExportedMetricByMetricName(
+                InMemoryMetricExporterProvider.LAST_CREATED_INSTANCE.getFinishedMetricItems());
+
+        // Assert jenkins.queue.count gauge is registered
+        assertThat(
+                "jenkins.queue.count metric must be registered and exported",
+                exportedMetrics.get(JenkinsMetrics.JENKINS_QUEUE_COUNT),
+                notNullValue());
+
+        // Assert jenkins.queue.waiting gauge is registered
+        assertThat(
+                "jenkins.queue.waiting metric must be registered and exported",
+                exportedMetrics.get(JenkinsMetrics.JENKINS_QUEUE_WAITING),
+                notNullValue());
+
+        // Assert jenkins.queue.blocked gauge is registered
+        assertThat(
+                "jenkins.queue.blocked metric must be registered and exported",
+                exportedMetrics.get(JenkinsMetrics.JENKINS_QUEUE_BLOCKED),
+                notNullValue());
+
+        // Assert jenkins.queue.buildable gauge is registered
+        assertThat(
+                "jenkins.queue.buildable metric must be registered and exported",
+                exportedMetrics.get(JenkinsMetrics.JENKINS_QUEUE_BUILDABLE),
+                notNullValue());
+
+        // Assert jenkins.queue.left counter is registered and incremented
+        MetricData queueLeft = exportedMetrics.get(JenkinsMetrics.JENKINS_QUEUE_LEFT);
+        assertThat("jenkins.queue.left counter must be registered and exported", queueLeft, notNullValue());
+        long leftCount = queueLeft.getLongSumData().getPoints().stream()
+                .mapToLong(p -> p.getValue())
+                .sum();
+        assertThat("At least one item must have left the queue", leftCount, greaterThanOrEqualTo(1L));
+
+        // Assert jenkins.queue.time_spent_millis counter is registered
+        assertThat(
+                "jenkins.queue.time_spent_millis counter must be registered and exported",
+                exportedMetrics.get(JenkinsMetrics.JENKINS_QUEUE_TIME_SPENT_MILLIS),
+                notNullValue());
+    }
+}