diff --git a/common_audio/BUILD.gn b/common_audio/BUILD.gn
index 50bd0f4022..4ff7986e82 100644
--- a/common_audio/BUILD.gn
+++ b/common_audio/BUILD.gn
@@ -15,16 +15,10 @@ rtc_static_library("common_audio") {
   sources = [
     "audio_converter.cc",
     "audio_converter.h",
-    "audio_ring_buffer.cc",
-    "audio_ring_buffer.h",
     "audio_util.cc",
-    "blocker.cc",
-    "blocker.h",
     "channel_buffer.cc",
     "channel_buffer.h",
     "include/audio_util.h",
-    "lapped_transform.cc",
-    "lapped_transform.h",
     "real_fourier.cc",
     "real_fourier.h",
     "real_fourier_ooura.cc",
@@ -349,12 +343,9 @@ if (rtc_include_tests) {
 
     sources = [
       "audio_converter_unittest.cc",
-      "audio_ring_buffer_unittest.cc",
       "audio_util_unittest.cc",
-      "blocker_unittest.cc",
       "channel_buffer_unittest.cc",
       "fir_filter_unittest.cc",
-      "lapped_transform_unittest.cc",
       "real_fourier_unittest.cc",
       "resampler/push_resampler_unittest.cc",
       "resampler/push_sinc_resampler_unittest.cc",
diff --git a/common_audio/ring_buffer.h b/common_audio/ring_buffer.h
index 0bbe879980..bcc40e107f 100644
--- a/common_audio/ring_buffer.h
+++ b/common_audio/ring_buffer.h
@@ -14,6 +14,8 @@
 #ifndef COMMON_AUDIO_RING_BUFFER_H_
 #define COMMON_AUDIO_RING_BUFFER_H_
 
+// TODO(alessiob): Used by AEC, AECm and AudioRingBuffer. Remove when possible.
+
 #ifdef __cplusplus
 extern "C" {
 #endif
diff --git a/modules/audio_coding/BUILD.gn b/modules/audio_coding/BUILD.gn
index de2aeb7a3c..0321c31529 100644
--- a/modules/audio_coding/BUILD.gn
+++ b/modules/audio_coding/BUILD.gn
@@ -2093,6 +2093,8 @@ if (rtc_include_tests) {
       "../../test:rtp_test_utils",
       "../../test:test_common",
       "../../test:test_support",
+      "codecs/opus/test",
+      "codecs/opus/test:test_unittest",
       "//testing/gtest",
       "//third_party/abseil-cpp/absl/memory",
     ]
diff --git a/modules/audio_coding/codecs/opus/opus_bandwidth_unittest.cc b/modules/audio_coding/codecs/opus/opus_bandwidth_unittest.cc
index 7f09c2aa1a..7e6b6268f4 100644
--- a/modules/audio_coding/codecs/opus/opus_bandwidth_unittest.cc
+++ b/modules/audio_coding/codecs/opus/opus_bandwidth_unittest.cc
@@ -11,8 +11,8 @@
 #include "api/audio_codecs/opus/audio_decoder_opus.h"
 #include "api/audio_codecs/opus/audio_encoder_opus.h"
 #include "common_audio/include/audio_util.h"
-#include "common_audio/lapped_transform.h"
 #include "common_audio/window_generator.h"
+#include "modules/audio_coding/codecs/opus/test/lapped_transform.h"
 #include "modules/audio_coding/neteq/tools/audio_loop.h"
 #include "test/field_trial.h"
 #include "test/gtest.h"
diff --git a/modules/audio_coding/codecs/opus/test/BUILD.gn b/modules/audio_coding/codecs/opus/test/BUILD.gn
new file mode 100644
index 0000000000..058dbfa03d
--- /dev/null
+++ b/modules/audio_coding/codecs/opus/test/BUILD.gn
@@ -0,0 +1,55 @@
+# Copyright (c) 2018 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.
+
+import("../../../../../webrtc.gni")
+
+visibility = [
+  ":*",
+  "../../../:*",
+]
+
+if (rtc_include_tests) {
+  rtc_static_library("test") {
+    testonly = true
+
+    sources = [
+      "audio_ring_buffer.cc",
+      "audio_ring_buffer.h",
+      "blocker.cc",
+      "blocker.h",
+      "lapped_transform.cc",
+      "lapped_transform.h",
+    ]
+
+    deps = [
+      "../../../../../common_audio:common_audio",
+      "../../../../../common_audio:common_audio_c",
+      "../../../../../rtc_base:checks",
+      "../../../../../rtc_base/memory:aligned_array",
+    ]
+  }
+
+  rtc_source_set("test_unittest") {
+    testonly = true
+
+    sources = [
+      "audio_ring_buffer_unittest.cc",
+      "blocker_unittest.cc",
+      "lapped_transform_unittest.cc",
+    ]
+
+    deps = [
+      ":test",
+      "../../../../../common_audio:common_audio",
+      "../../../../../common_audio:common_audio_c",
+      "../../../../../rtc_base:rtc_base_approved",
+      "../../../../../test:test_support",
+      "//testing/gtest",
+    ]
+  }
+}
diff --git a/common_audio/audio_ring_buffer.cc b/modules/audio_coding/codecs/opus/test/audio_ring_buffer.cc
similarity index 97%
rename from common_audio/audio_ring_buffer.cc
rename to modules/audio_coding/codecs/opus/test/audio_ring_buffer.cc
index b3bdc252f6..2a71b43d2c 100644
--- a/common_audio/audio_ring_buffer.cc
+++ b/modules/audio_coding/codecs/opus/test/audio_ring_buffer.cc
@@ -8,7 +8,7 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include "common_audio/audio_ring_buffer.h"
+#include "modules/audio_coding/codecs/opus/test/audio_ring_buffer.h"
 
 #include "common_audio/ring_buffer.h"
 #include "rtc_base/checks.h"
diff --git a/common_audio/audio_ring_buffer.h b/modules/audio_coding/codecs/opus/test/audio_ring_buffer.h
similarity index 90%
rename from common_audio/audio_ring_buffer.h
rename to modules/audio_coding/codecs/opus/test/audio_ring_buffer.h
index 67d24f00d5..a89dfd8ca7 100644
--- a/common_audio/audio_ring_buffer.h
+++ b/modules/audio_coding/codecs/opus/test/audio_ring_buffer.h
@@ -7,8 +7,8 @@
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
-#ifndef COMMON_AUDIO_AUDIO_RING_BUFFER_H_
-#define COMMON_AUDIO_AUDIO_RING_BUFFER_H_
+#ifndef MODULES_AUDIO_CODING_CODECS_OPUS_TEST_AUDIO_RING_BUFFER_H_
+#define MODULES_AUDIO_CODING_CODECS_OPUS_TEST_AUDIO_RING_BUFFER_H_
 
 #include <stddef.h>
 
@@ -54,4 +54,4 @@ class AudioRingBuffer final {
 
 }  // namespace webrtc
 
-#endif  // COMMON_AUDIO_AUDIO_RING_BUFFER_H_
+#endif  // MODULES_AUDIO_CODING_CODECS_OPUS_TEST_AUDIO_RING_BUFFER_H_
diff --git a/common_audio/audio_ring_buffer_unittest.cc b/modules/audio_coding/codecs/opus/test/audio_ring_buffer_unittest.cc
similarity index 98%
rename from common_audio/audio_ring_buffer_unittest.cc
rename to modules/audio_coding/codecs/opus/test/audio_ring_buffer_unittest.cc
index d411195aa7..e26df3a83c 100644
--- a/common_audio/audio_ring_buffer_unittest.cc
+++ b/modules/audio_coding/codecs/opus/test/audio_ring_buffer_unittest.cc
@@ -10,7 +10,7 @@
 
 #include <memory>
 
-#include "common_audio/audio_ring_buffer.h"
+#include "modules/audio_coding/codecs/opus/test/audio_ring_buffer.h"
 
 #include "common_audio/channel_buffer.h"
 #include "test/gtest.h"
diff --git a/common_audio/blocker.cc b/modules/audio_coding/codecs/opus/test/blocker.cc
similarity index 99%
rename from common_audio/blocker.cc
rename to modules/audio_coding/codecs/opus/test/blocker.cc
index 3dc8ed8040..7f102b54af 100644
--- a/common_audio/blocker.cc
+++ b/modules/audio_coding/codecs/opus/test/blocker.cc
@@ -8,7 +8,7 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include "common_audio/blocker.h"
+#include "modules/audio_coding/codecs/opus/test/blocker.h"
 
 #include <string.h>
 
diff --git a/common_audio/blocker.h b/modules/audio_coding/codecs/opus/test/blocker.h
similarity index 95%
rename from common_audio/blocker.h
rename to modules/audio_coding/codecs/opus/test/blocker.h
index 9bce896dfe..26177bcadd 100644
--- a/common_audio/blocker.h
+++ b/modules/audio_coding/codecs/opus/test/blocker.h
@@ -8,13 +8,13 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#ifndef COMMON_AUDIO_BLOCKER_H_
-#define COMMON_AUDIO_BLOCKER_H_
+#ifndef MODULES_AUDIO_CODING_CODECS_OPUS_TEST_BLOCKER_H_
+#define MODULES_AUDIO_CODING_CODECS_OPUS_TEST_BLOCKER_H_
 
 #include <memory>
 
-#include "common_audio/audio_ring_buffer.h"
 #include "common_audio/channel_buffer.h"
+#include "modules/audio_coding/codecs/opus/test/audio_ring_buffer.h"
 
 namespace webrtc {
 
@@ -124,4 +124,4 @@ class Blocker {
 
 }  // namespace webrtc
 
-#endif  // COMMON_AUDIO_BLOCKER_H_
+#endif  // MODULES_AUDIO_CODING_CODECS_OPUS_TEST_BLOCKER_H_
diff --git a/common_audio/blocker_unittest.cc b/modules/audio_coding/codecs/opus/test/blocker_unittest.cc
similarity index 99%
rename from common_audio/blocker_unittest.cc
rename to modules/audio_coding/codecs/opus/test/blocker_unittest.cc
index 85a24f6847..bfdb2e64b3 100644
--- a/common_audio/blocker_unittest.cc
+++ b/modules/audio_coding/codecs/opus/test/blocker_unittest.cc
@@ -10,7 +10,7 @@
 
 #include <memory>
 
-#include "common_audio/blocker.h"
+#include "modules/audio_coding/codecs/opus/test/blocker.h"
 
 #include "rtc_base/arraysize.h"
 #include "test/gtest.h"
diff --git a/common_audio/lapped_transform.cc b/modules/audio_coding/codecs/opus/test/lapped_transform.cc
similarity index 98%
rename from common_audio/lapped_transform.cc
rename to modules/audio_coding/codecs/opus/test/lapped_transform.cc
index 72c2ad79f6..b1a6526bba 100644
--- a/common_audio/lapped_transform.cc
+++ b/modules/audio_coding/codecs/opus/test/lapped_transform.cc
@@ -8,7 +8,7 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include "common_audio/lapped_transform.h"
+#include "modules/audio_coding/codecs/opus/test/lapped_transform.h"
 
 #include <algorithm>
 #include <cstdlib>
diff --git a/common_audio/lapped_transform.h b/modules/audio_coding/codecs/opus/test/lapped_transform.h
similarity index 93%
rename from common_audio/lapped_transform.h
rename to modules/audio_coding/codecs/opus/test/lapped_transform.h
index 1ab2a9fee7..e42d9e3500 100644
--- a/common_audio/lapped_transform.h
+++ b/modules/audio_coding/codecs/opus/test/lapped_transform.h
@@ -8,14 +8,14 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#ifndef COMMON_AUDIO_LAPPED_TRANSFORM_H_
-#define COMMON_AUDIO_LAPPED_TRANSFORM_H_
+#ifndef MODULES_AUDIO_CODING_CODECS_OPUS_TEST_LAPPED_TRANSFORM_H_
+#define MODULES_AUDIO_CODING_CODECS_OPUS_TEST_LAPPED_TRANSFORM_H_
 
 #include <complex>
 #include <memory>
 
-#include "common_audio/blocker.h"
 #include "common_audio/real_fourier.h"
+#include "modules/audio_coding/codecs/opus/test/blocker.h"
 #include "rtc_base/memory/aligned_array.h"
 
 namespace webrtc {
@@ -119,6 +119,7 @@ class LappedTransform {
   Callback* const block_processor_;
   Blocker blocker_;
 
+  // TODO(alessiob): Replace RealFourier with a different FFT library.
   std::unique_ptr<RealFourier> fft_;
   const size_t cplx_length_;
   AlignedArray<float> real_buf_;
@@ -128,4 +129,4 @@ class LappedTransform {
 
 }  // namespace webrtc
 
-#endif  // COMMON_AUDIO_LAPPED_TRANSFORM_H_
+#endif  // MODULES_AUDIO_CODING_CODECS_OPUS_TEST_LAPPED_TRANSFORM_H_
diff --git a/common_audio/lapped_transform_unittest.cc b/modules/audio_coding/codecs/opus/test/lapped_transform_unittest.cc
similarity index 98%
rename from common_audio/lapped_transform_unittest.cc
rename to modules/audio_coding/codecs/opus/test/lapped_transform_unittest.cc
index 687df8986a..1003ed52e5 100644
--- a/common_audio/lapped_transform_unittest.cc
+++ b/modules/audio_coding/codecs/opus/test/lapped_transform_unittest.cc
@@ -8,7 +8,7 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include "common_audio/lapped_transform.h"
+#include "modules/audio_coding/codecs/opus/test/lapped_transform.h"
 
 #include <algorithm>
 #include <cmath>