@Test
public void invoke() throws Exception {

    SQSMessageProcessorRequest sqsMessageProcessorRequest = new SQSMessageProcessorRequest();
    sqsMessageProcessorRequest.setMessages(MESSAGES);
    //fake json string
    ByteBuffer byteBuffer = ByteBuffer.wrap("{\"key1\":value1,\"key2\":value2}".getBytes());
    InvokeResult invokeResult = mock(InvokeResult.class);
    when(invokeResult.getPayload()).thenReturn(byteBuffer);
    when(lambda.invoke(any(InvokeRequest.class))).thenReturn(invokeResult);
    messageProcessorProxy.invoke(sqsMessageProcessorRequest);
}