Add test

javaagent-tooling/testing-java18/build.gradle.kts

@@ -0,0 +1,13 @@
+plugins {
+  id("otel.javaagent-instrumentation")
+}
+
+dependencies {
+  // To be able to have it as part of agent,
+  // this dependency needs to be added as "testInstrumentation", not as "testImplementation"
+  testInstrumentation(project(":instrumentation:resources:library"))
+}
+
+otelJava {
+  minJavaVersionSupported.set(JavaVersion.VERSION_18)
+}

javaagent-tooling/testing-java18/src/test/java/io/opentelemetry/javaagent/tooling/inetaddress/InetAddressResolverTest.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.javaagent.tooling.inetaddress;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.net.InetAddress;
+import org.junit.jupiter.api.Test;
+
+public class InetAddressResolverTest {
+
+  @Test
+  void agentStartShouldNotTriggerLoadingCustomInetAddressResolvers() throws Exception {
+    // Agent start should not trigger loading (and instantiating) custom InetAddress resolvers
+    assertThat(TestAddressResolver.isInstantiated()).isFalse();
+
+    // Trigger loading (and instantiating) custom InetAddress resolvers manually
+    InetAddress.getAllByName("test");
+
+    // Verify that custom InetAddress resolver loaded and instantiated
+    assertThat(TestAddressResolver.isInstantiated()).isTrue();
+  }
+}

javaagent-tooling/testing-java18/src/test/java/io/opentelemetry/javaagent/tooling/inetaddress/TestAddressResolver.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.javaagent.tooling.inetaddress;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.net.spi.InetAddressResolver;
+import java.util.stream.Stream;
+
+public class TestAddressResolver implements InetAddressResolver {
+
+  private static volatile boolean instantiated = false;
+
+  @SuppressWarnings("StaticAssignmentInConstructor")
+  public TestAddressResolver() {
+    TestAddressResolver.instantiated = true;
+  }
+
+  public static boolean isInstantiated() {
+    return instantiated;
+  }
+
+  @Override
+  public Stream<InetAddress> lookupByName(String host, LookupPolicy lookupPolicy)
+      throws UnknownHostException {
+    if (host.equals("test")) {
+      return Stream.of(InetAddress.getByAddress(new byte[] {127, 0, 0, 1}));
+    }
+    throw new UnknownHostException();
+  }
+
+  @Override
+  public String lookupByAddress(byte[] addr) {
+    throw new UnsupportedOperationException();
+  }
+}

javaagent-tooling/testing-java18/src/test/java/io/opentelemetry/javaagent/tooling/inetaddress/TestAddressResolverProvider.java

@@ -0,0 +1,22 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.javaagent.tooling.inetaddress;
+
+import java.net.spi.InetAddressResolver;
+import java.net.spi.InetAddressResolverProvider;
+
+public class TestAddressResolverProvider extends InetAddressResolverProvider {
+
+  @Override
+  public InetAddressResolver get(Configuration configuration) {
+    return new TestAddressResolver();
+  }
+
+  @Override
+  public String name() {
+    return "Test Internet Address Resolver Provider";
+  }
+}

javaagent-tooling/testing-java18/src/test/resources/META-INF/services/java.net.spi.InetAddressResolverProvider

@@ -0,0 +1 @@
+io.opentelemetry.javaagent.tooling.inetaddress.TestAddressResolverProvider

settings.gradle.kts

@@ -121,6 +121,7 @@ include(":javaagent-bootstrap")
 include(":javaagent-extension-api")
 include(":javaagent-tooling")
 include(":javaagent-tooling:javaagent-tooling-java9")
+include(":javaagent-tooling:testing-java18")
 include(":javaagent-internal-logging-application")
 include(":javaagent-internal-logging-simple")
 include(":javaagent")