### Question:
FluidRegistry { public static synchronized void initialize(Vertx vertx, FluidConfig config) { sinks.putAll(SourceAndSinkBuilder.createSinksFromConfiguration(vertx, config)); sources.putAll(SourceAndSinkBuilder.createSourcesFromConfiguration(vertx, config)); } private  FluidRegistry(); static synchronized void initialize(Vertx vertx, FluidConfig config); static void reset(); static synchronized void register(Source<T> source); static synchronized void register(Sink<T> sink); static synchronized void register(String name, Source<T> source); static synchronized void register(String name, Sink<T> sink); static synchronized void unregisterSource(String name); static synchronized void unregisterSink(String name); @SuppressWarnings("unchecked") static Source<T> source(String name); @SuppressWarnings("unchecked") static Sink<T> sink(String name); @SuppressWarnings({"unused", "unchecked"}) static Source<T> source(String name, Class<T> clazz);  }### Answer:
@Test public void testInitialize() { Fluid fluid = Fluid.create(); assertThat(FluidRegistry.source("unknown")).isNull(); assertThat(FluidRegistry.sink("unknown")).isNull(); fluid.vertx().close(); }