@Test
  public void filterMatchesEmpty() {
    List<String> candidates = ImmutableList.of("foo", "bar");
    assertThat(filterMatches(candidates, null, null), is(candidates));
    assertThat(filterMatches(null, null, null), is(Collections.emptyList()));
  }
Test that a null pattern returns all candidates for iflterMatches.
Also verify that null candidates result in an empty result list.
standalone-metastore/metastore-tools/tools-common/src/test/java/org/apache/hadoop/hive/metastore/tools/UtilTest.java