Add algorithm for Residual Echo Detector.

webrtc/modules/audio_processing/echo_detector/normalized_covariance_estimator_unittest.cc

Index: webrtc/modules/audio_processing/echo_detector/normalized_covariance_estimator_unittest.cc
diff --git a/webrtc/modules/audio_processing/echo_detector/normalized_covariance_estimator_unittest.cc b/webrtc/modules/audio_processing/echo_detector/normalized_covariance_estimator_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..04b3a92fb5ed99f67b703bcc45c6976aeac75432
--- /dev/null
+++ b/webrtc/modules/audio_processing/echo_detector/normalized_covariance_estimator_unittest.cc
@@ -0,0 +1,40 @@
+
+/*
+ *  Copyright (c) 2016 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/echo_detector/normalized_covariance_estimator.h"
+#include "webrtc/test/gtest.h"
+
+namespace webrtc {
+
+TEST(NormalizedCovarianceEstimatorTests, IdenticalSignalTest) {
+  NormalizedCovarianceEstimator test_estimator;
+  for (size_t i = 0; i < 10000; i++) {
+    test_estimator.Update(1.f, 0.f, 1.f, 1.f, 0.f, 1.f);
+    test_estimator.Update(-1.f, 0.f, 1.f, -1.f, 0.f, 1.f);
+  }
+  // A normalized covariance value close to 1 is expected.
+  EXPECT_NEAR(1.f, test_estimator.normalized_cross_correlation(), 0.01f);
+  test_estimator.Clear();
+  EXPECT_EQ(0.f, test_estimator.normalized_cross_correlation());
+}
+
+TEST(NormalizedCovarianceEstimatorTests, OppositeSignalTest) {
+  NormalizedCovarianceEstimator test_estimator;
+  // Insert the same value many times.
+  for (size_t i = 0; i < 10000; i++) {
+    test_estimator.Update(1.f, 0.f, 1.f, -1.f, 0.f, 1.f);
+    test_estimator.Update(-1.f, 0.f, 1.f, 1.f, 0.f, 1.f);
+  }
+  // A normalized covariance value close to -1 is expected.
+  EXPECT_NEAR(-1.f, test_estimator.normalized_cross_correlation(), 0.01f);
+}
+
+}  // namespace webrtc