@Override
          public void testAndAssert(RouterErrorCode expectedError) throws Exception {
            future = router.deleteBlob(blobIdString, null);
            router.close();
            assertFailureAndCheckErrorCode(future, expectedError);
          }
Test the case how a {@link DeleteManager} acts when a router is closed, and when there are inflight
operations. Setting servers to not respond any requests, so {@link DeleteOperation} can be "in flight".
ambry-router/src/test/java/com/github/ambry/router/DeleteManagerTest.java