@Test
public void testGetSignedDomainServiceException() {

    MockS3ChangeLogStore store = new MockS3ChangeLogStore();
    
    when(store.awsS3Client.getObject(any(GetObjectRequest.class))).thenThrow(new AmazonServiceException("failed server operation"));
    assertNull(store.getSignedDomain(store.awsS3Client, "iaas"));
}