@Test
public void testMergeThree() {

    DatasetMetadataMerger datasetMetadataMerger = new DatasetMetadataMerger();
    DatasetMetadata metadata1 = createDatasetMetadata( URL_1 );
    DatasetMetadata metadata2 = createDatasetMetadata( URL_2, URL_3 );
    DatasetMetadata metadata3 = createDatasetMetadata( URL_4 );
    DatasetMetadata mergedMetadata = datasetMetadataMerger.merge( asList( metadata1, metadata2, metadata3 ) );
    List<MetadataUrl> metadataUrls = mergedMetadata.getMetadataUrls();
    assertThat( metadataUrls.size(), is( 4 ) );
}