/**
 * @license
 * Copyright 2023 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import { Unsubscribe } from '../api/reference_impl';
import { ExistenceFilterMismatchInfo } from './testing_hooks_spi';
/**
 * Testing hooks for use by Firestore's integration test suite to reach into the
 * SDK internals to validate logic and behavior that is not visible from the
 * public API surface.
 *
 * @internal
 */
export declare class TestingHooks {
    private constructor();
    /**
     * Registers a callback to be notified when an existence filter mismatch
     * occurs in the Watch listen stream.
     *
     * The relative order in which callbacks are notified is unspecified; do not
     * rely on any particular ordering. If a given callback is registered multiple
     * times then it will be notified multiple times, once per registration.
     *
     * @param callback - the callback to invoke upon existence filter mismatch.
     *
     * @returns a function that, when called, unregisters the given callback; only
     * the first invocation of the returned function does anything; all subsequent
     * invocations do nothing.
     */
    static onExistenceFilterMismatch(callback: ExistenceFilterMismatchCallback): Unsubscribe;
}
/**
 * The signature of callbacks registered with
 * `TestingUtils.onExistenceFilterMismatch()`.
 *
 * The return value, if any, is ignored.
 *
 * @internal
 */
export type ExistenceFilterMismatchCallback = (info: ExistenceFilterMismatchInfo) => unknown;