Convert internal-url-class-loader javaagent integration tests

instrumentation/internal/internal-url-class-loader/javaagent-integration-tests/src/test/java/AddUrlTest.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.catchThrowable;
+
+import java.net.URL;
+import java.net.URLClassLoader;
+import org.apache.commons.io.IOUtils;
+import org.apache.commons.lang3.SystemUtils;
+import org.junit.jupiter.api.Test;
+
+class AddUrlTest {
+
+  @Test
+  void testShouldInstrumentClassAfterItIsLoadedViaAddUrl() throws Exception {
+    TestUrlClassLoader loader = new TestUrlClassLoader();
+
+    // this is just to verify the assumption that TestURLClassLoader is not finding SystemUtils via
+    // the test class path (in which case the verification below would not be very meaningful)
+    Throwable thrown =
+        catchThrowable(
+            () -> {
+              loader.loadClass(SystemUtils.class.getName());
+            });
+
+    assertThat(thrown).isInstanceOf(ClassNotFoundException.class);
+
+    // loading a class in the URLClassLoader in order to trigger
+    // a negative cache hit on org.apache.commons.lang3.SystemUtils
+    loader.addURL(IOUtils.class.getProtectionDomain().getCodeSource().getLocation());
+    loader.loadClass(IOUtils.class.getName());
+
+    loader.addURL(SystemUtils.class.getProtectionDomain().getCodeSource().getLocation());
+    Class<?> clazz = loader.loadClass(SystemUtils.class.getName());
+
+    assertThat(clazz.getClassLoader()).isEqualTo(loader);
+    assertThat(clazz.getMethod("getHostName").invoke(null)).isEqualTo("not-the-host-name");
+  }
+
+  static class TestUrlClassLoader extends URLClassLoader {
+
+    TestUrlClassLoader() {
+      super(new URL[0], null);
+    }
+
+    // silence CodeNarc. URLClassLoader#addURL is protected, this method is public
+    @SuppressWarnings("UnnecessaryOverridingMethod")
+    @Override
+    public void addURL(URL url) {
+      super.addURL(url);
+    }
+  }
+}