add test for only custom yaml

Author: SylvainJuge

jmx-scraper/src/integrationTest/java/io/opentelemetry/contrib/jmxscraper/target_systems/CustomIntegrationTest.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.jmxscraper.target_systems;
+
+import io.opentelemetry.contrib.jmxscraper.JmxScraperContainer;
+import io.opentelemetry.contrib.jmxscraper.TestAppContainer;
+import java.nio.file.Path;
+import org.testcontainers.containers.GenericContainer;
+import org.testcontainers.containers.wait.strategy.Wait;
+
+public class CustomIntegrationTest extends TargetSystemIntegrationTest {
+
+  @Override
+  protected GenericContainer<?> createTargetContainer(int jmxPort) {
+    // reusing test application for custom yaml
+    //noinspection resource
+    return new TestAppContainer()
+        .withJmxPort(jmxPort)
+        .withExposedPorts(jmxPort)
+        .waitingFor(Wait.forListeningPorts(jmxPort));
+  }
+
+  @Override
+  protected JmxScraperContainer customizeScraperContainer(
+      JmxScraperContainer scraper, GenericContainer<?> target, Path tempDir) {
+    // only testing custom yaml
+    return scraper.withCustomYaml("custom-metrics.yaml");
+  }
+
+  @Override
+  protected MetricsVerifier createMetricsVerifier() {
+    return MetricsVerifier.create()
+        // custom metric in custom-metrics.yaml
+        .add(
+            "custom.jvm.uptime",
+            metric ->
+                metric
+                    .hasDescription("JVM uptime in milliseconds")
+                    .hasUnit("ms")
+                    .isCounter()
+                    .hasDataPointsWithoutAttributes());
+  }
+}