@Test
  public void testDownloadBlobException() {
    BlobStorageException ex = mockStorageException(BlobErrorCode.INTERNAL_ERROR);
    when(mockBlockBlobAsyncClient.downloadWithResponse(any(), any(), any(), anyBoolean())).thenReturn(Mono.error(ex));
    expectCloudStorageException(() -> downloadBlob(blobId), BlobStorageException.class);
    verifyDownloadErrorMetrics();
  }
Test download when blob throws exception.
ambry-cloud/src/test/java/com/github/ambry/cloud/azure/AzureCloudDestinationTest.java