First try on a fake analog volume control interface for use in audioproc_f.

webrtc/modules/audio_processing/test/analog_volume_mapper_unittest.cc

+/*
+ *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/modules/audio_processing/test/identity_analog_volume_mapper.h"
+#include "webrtc/test/gtest.h"
+

[aleloi, 2017/04/21 09:39:14]

The idea is to submit all subclasses of the VolumeMapper to this test. Perhaps
it would be better to make the test call a function that takes an
*AnalogVolumeMapper instead.

[AleBzk, 2017/04/21 10:35:49]

Acknowledged.

+TEST(AnalogVolumeMapper, GainCurveShouldBeMonotone) {
+  webrtc::IdentityAnalogLevelMapper level_mapper;
+  float last_level = level_mapper.get_scaling_factor();
+  RTC_DCHECK_LE(0.f, last_level);
+
+  for (int i = 0; i < 65535; ++i) {
+    level_mapper.set_analog_level(i);
+    const float current_level = level_mapper.get_scaling_factor();
+    RTC_DCHECK_LE(last_level, current_level);
+
+    last_level = current_level;
+  }
+}