chromium/components/reporting/util/test_support_callbacks.h

// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_REPORTING_UTIL_TEST_SUPPORT_CALLBACKS_H_
#define COMPONENTS_REPORTING_UTIL_TEST_SUPPORT_CALLBACKS_H_

#include <tuple>
#include <utility>

#include "base/atomic_ref_count.h"
#include "base/functional/bind.h"
#include "base/functional/callback_forward.h"
#include "base/functional/callback_helpers.h"
#include "base/logging.h"
#include "base/memory/weak_ptr.h"
#include "base/run_loop.h"
#include "base/synchronization/lock.h"
#include "base/task/bind_post_task.h"
#include "base/task/sequenced_task_runner.h"
#include "base/thread_annotations.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace reporting::test {

// Usage (in tests only):
//
//   TestMultiEvent<ResType1, Restype2, ...> e;
//
//   ... Do some async work passing e.cb() as a completion callback of
//   base::OnceCallback<void(ResType1, Restype2, ...)> type which also may
//   perform some other action specified by |done| callback provided by the
//   caller. Now wait for e.cb() to be called and return the collected results.
//
//   std::tie(res1, res2, ...) = e.result();
//
template <typename... ResType>
class TestMultiEvent { … };

// Usage (in tests only):
//
//   TestEvent<ResType> e;
//
//   ... Do some async work passing e.cb() as a completion callback of
//   base::OnceCallback<void(ResType res)> type which also may perform some
//   other action specified by |done| callback provided by the caller.
//   Now wait for e.cb() to be called and return the collected result.
//
//   ... = e.result();
//
template <typename ResType>
class TestEvent : public TestMultiEvent<ResType> { … };

// Usage (in tests only):
//
//  TestCallbackWaiter waiter;
//  ... do something
//  waiter.Wait();
//
//  or, with multithreadeded activity:
//
//  TestCallbackWaiter waiter;
//  waiter.Attach(N);  // N - is a number of asynchronous actions
//  ...
//  waiter.Wait();
//
//  And  in each of N actions: waiter.Signal(); when done

class TestCallbackWaiter : public TestEvent<bool> { … };

// RAII wrapper for TestCallbackWaiter.
//
// Usage:
// {
//   TestCallbackAutoWaiter waiter;  // Implicitly Attach(1);
//   ...
//   Launch async activity, which will eventually do waiter.Signal();
//   ...
// }   // Here the waiter will automatically wait.

class TestCallbackAutoWaiter : public TestCallbackWaiter { … };
}  // namespace reporting::test

#endif  // COMPONENTS_REPORTING_UTIL_TEST_SUPPORT_CALLBACKS_H_