ArgumentCaptor<DtFetchOperation> captor =
ArgumentCaptor.forClass(DtFetchOperation.class);
verify(mockCluster).execute(captor.capture());
DtFetchOperation operation = captor.getValue();
RiakDtPB.DtFetchReq.Builder builder =
(RiakDtPB.DtFetchReq.Builder) Whitebox.getInternalState(operation, "reqBuilder");
assertEquals("type", builder.getType().toStringUtf8());
assertEquals("bucket", builder.getBucket().toStringUtf8());