public static BadRequestException namespaceNotExists() {
    return new BadRequestException("namespace not exist.");
  }
@Test
  public void testNamespaceNotExists() {
    BadRequestException namespaceNotExists = BadRequestException.namespaceNotExists();
    assertEquals("namespace not exist.", namespaceNotExists.getMessage());

    BadRequestException namespaceNotExists2 = BadRequestException.namespaceNotExists(appId, clusterName, namespaceName);
    assertEquals("namespace not exist for appId:app-1001 clusterName:test namespaceName:application", namespaceNotExists2.getMessage());
  }