@Test
public void testGrantAccessOnly()   {

    metadata.commit(() -> {
        this.opsAccessProvider.grantAccess(FEED_ID1, USER1, USER2);
    }, MetadataAccess.SERVICE);
    
    metadata.commit(() -> {
        this.opsAccessProvider.grantAccessOnly(FEED_ID1, USER3);
    }, MetadataAccess.SERVICE);
    
    Set<Principal> set1 = metadata.read(() -> {
        return this.opsAccessProvider.getPrincipals(FEED_ID1);
    }, MetadataAccess.SERVICE);
    
    assertThat(set1)
        .hasSize(1)
        .containsOnly(USER3);
}