@Test
  public void testRemoveNamespaceProperties() {
    Namespace namespace = Namespace.of("dbname_remove");

    catalog.createNamespace(namespace, meta);

    catalog.removeProperties(namespace, ImmutableSet.of("comment", "owner"));

    Database database = null;
    try {
      database = HIVE_METASTORE_EXTENSION.metastoreClient().getDatabase(namespace.level(0));
    } catch (TException e) {
      Assert.fail();
    }
    assertThat(database.getParameters()).doesNotContainKey("owner");
    assertThat(database.getParameters()).containsEntry("group", "iceberg");

    assertThatThrownBy(
        () ->
            catalog.removeProperties(
                Namespace.of("db2", "db2", "ns2"), ImmutableSet.of("comment", "owner")))
        .isInstanceOf(NoSuchNamespaceException.class)
        .hasMessage("Namespace does not exist: db2.db2.ns2");
  }
Run all the tests from abstract of {@link CatalogTests} with few specific tests related to HIVE.
iceberg/iceberg-catalog/src/test/java/org/apache/iceberg/hive/TestHiveCatalog.java