@Test
void provide_test() {

    MetadataStatementsProvider providerA = mock(MetadataStatementsProvider.class);
    Map<AAGUID, Set<MetadataStatement>> mapA = new HashMap<>();
    mapA.put(new AAGUID("df495bdc-223a-429d-9f0e-ebfa29155812"), new HashSet<>());
    when(providerA.provide()).thenReturn(mapA);
    MetadataStatementsProvider providerB = mock(MetadataStatementsProvider.class);
    Map<AAGUID, Set<MetadataStatement>> mapB = new HashMap<>();
    mapB.put(new AAGUID("d075c221-6a37-4c61-80c7-11254460d5bb"), new HashSet<>());
    when(providerB.provide()).thenReturn(mapB);
    AggregatingMetadataStatementsProvider target = new AggregatingMetadataStatementsProvider(Arrays.asList(providerA, providerB));
    assertThat(target.provide()).containsOnlyKeys(new AAGUID("df495bdc-223a-429d-9f0e-ebfa29155812"), new AAGUID("d075c221-6a37-4c61-80c7-11254460d5bb"));
}