Convert internal-reflection tests from groovy to java

instrumentation/internal/internal-reflection/javaagent-integration-tests/src/test/java/ReflectionTest.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import io.opentelemetry.javaagent.bootstrap.VirtualFieldAccessorMarker;
+import io.opentelemetry.javaagent.bootstrap.VirtualFieldInstalledMarker;
+import java.io.ObjectStreamClass;
+import java.io.Serializable;
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import org.junit.jupiter.api.Test;
+
+public class ReflectionTest {
+
+  @Test
+  void testOurFieldsAndMethodsAreNotVisibleWithReflection() {
+    TestClass test = new TestClass();
+
+    assertThat(test.testMethod()).isEqualTo("instrumented");
+    assertThat(test.testMethod2()).isEqualTo("instrumented");
+
+    for (Field field : TestClass.class.getDeclaredFields()) {
+      assertThat(field.getName()).doesNotStartWith("__opentelemetry");
+    }
+
+    for (Method method : TestClass.class.getDeclaredMethods()) {
+      assertThat(method.getName()).doesNotStartWith("__opentelemetry");
+    }
+
+    // although marker interfaces are removed from getInterfaces() result class is still assignable
+    // to them
+    assertThat(VirtualFieldInstalledMarker.class.isAssignableFrom(TestClass.class)).isTrue();
+    assertThat(VirtualFieldAccessorMarker.class.isAssignableFrom(TestClass.class)).isTrue();
+    assertThat(TestClass.class.getInterfaces().length).isEqualTo(2);
+    assertThat(TestClass.class.getInterfaces()).isInstanceOfAny(Runnable.class, Serializable.class);
+  }
+
+  @Test
+  void testGeneratedSerialVersionUid() {
+    // expected value is computed with serialver utility that comes with jdk
+    assertThat(ObjectStreamClass.lookup(TestClass.class).getSerialVersionUID())
+        .isEqualTo(-1508684692096503670L);
+    assertThat(TestClass.class.getDeclaredFields().length).isEqualTo(0);
+  }
+}