New test, which fails

Describes the issue though: AWS can't deserialize the event if it
can't tell what the input type is at runtime. Erasure is preventing
that.

Author: Matt Whelan

src/test/java/com/newrelic/opentracing/aws/ReflectionTest.java

@@ -0,0 +1,44 @@
+package com.newrelic.opentracing.aws;
+
+import com.amazonaws.services.lambda.runtime.Context;
+import com.amazonaws.services.lambda.runtime.RequestHandler;
+import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyRequestEvent;
+import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyResponseEvent;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.lang.reflect.Method;
+import java.util.Arrays;
+
+import static org.junit.Assert.assertEquals;
+
+public class ReflectionTest {
+    private static final int SYNTHETIC_MODIFIER = 0x1000;
+
+    private Object handler;
+
+    @Before
+    public void setup() {
+        handler = new TestHandler();
+    }
+
+    @Test
+    public void testInputReflection() {
+        // Ignoring synthetics, we expect handleRequest to take the declared type as its first arg.
+        // This is necessary for correct payload deserialization.
+        final Method handleRequest = Arrays.stream(handler.getClass().getMethods())
+                .filter(m -> ((m.getModifiers() & SYNTHETIC_MODIFIER) == 0)
+                    && m.getName().equals("handleRequest"))
+                .findFirst()
+                .orElseThrow(AssertionError::new);
+
+        assertEquals(APIGatewayProxyRequestEvent.class, handleRequest.getParameterTypes()[0]);
+    }
+
+    public static class TestHandler implements TracingRequestHandler<APIGatewayProxyRequestEvent, APIGatewayProxyResponseEvent> {
+        @Override
+        public APIGatewayProxyResponseEvent doHandleRequest(APIGatewayProxyRequestEvent apiGatewayProxyRequestEvent, Context context) {
+            return new APIGatewayProxyResponseEvent();
+        }
+    }
+}