diff --git a/CHANGELOG.md b/CHANGELOG.md
index b1062d5..c54d203 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,7 +16,8 @@ The issue #16 changes its public member function. But it is referred internally
 - [Issue #11](https://github.com/suikan4github/rpp_driver/issues/11) Fails to compile in MSVC. 
 - [Issue #17](https://github.com/suikan4github/rpp_driver/issues/17) The mock of the GpioBasic has the wrong definition. 
 - [Issue #18](https://github.com/suikan4github/rpp_driver/issues/18) The constructor of the MockI2sSlaveDuplex.hpp is missing.
-### Security
+- [Issue #19](https://github.com/suikan4github/rpp_driver/issues/19) The Mock of the rpp_driver::Adau1361 is missing.
+ ### Security
 ### Known Issue
 
 ## [v1.0.0] 2024-10-03
diff --git a/src/codec/adau1361.hpp b/src/codec/adau1361.hpp
index 74ec5f9..d21657d 100644
--- a/src/codec/adau1361.hpp
+++ b/src/codec/adau1361.hpp
@@ -159,6 +159,24 @@ class Adau1361 {
   bool line_output_mute_;
   bool hp_output_mute_;  // headphone
 };
+
+#if __has_include(<gmock/gmock.h>)
+// GCOVR_EXCL_START
+class MockAdau1361 : public Adau1361 {
+ public:
+  MockAdau1361(Adau1361Lower& adau1361_lower)
+      : Adau1361(48'000, 12'000'000, adau1361_lower) {
+  }  // with dummy fs and dummy mclock
+
+  MOCK_METHOD0(Start, void(void));
+  MOCK_METHOD3(SetGain,
+               void(CodecChannel channel, float left_gain, float right_gain));
+  MOCK_METHOD2(Mute, void(CodecChannel channel, bool mute));
+  MOCK_METHOD1(Mute, void(CodecChannel channel));
+};
+// GCOVR_EXCL_STOP
+#endif  // __has_include(<gmock/gmock.h>)
+
 }  // namespace rpp_driver
 
 #endif /* PICO_DRIVER_SRC_CODEC_ADAU1361_HPP_ */
\ No newline at end of file
diff --git a/src/i2s/i2sslaveduplex.hpp b/src/i2s/i2sslaveduplex.hpp
index a8d419c..eb84a21 100644
--- a/src/i2s/i2sslaveduplex.hpp
+++ b/src/i2s/i2sslaveduplex.hpp
@@ -154,15 +154,15 @@ class I2sSlaveDuplex {
 class MockI2sSlaveDuplex : public I2sSlaveDuplex {
  public:
   MockI2sSlaveDuplex(SdkWrapper &sdk)
-      : I2sSlaveDuplex(sdk, 0, 0) {}  //  // 0 is dummy. We don't care.
+      : I2sSlaveDuplex(sdk, 0, 0) {}  // 0 is dummy. We don't care.
   MOCK_METHOD0(GetStateMachine, uint32_t(void));
   MOCK_METHOD0(Start, void(void));
   MOCK_METHOD0(Stop, void(void));
   MOCK_METHOD1(PutFifoBlocking, void(int32_t value));
   MOCK_METHOD0(GetFifoBlocking, int32_t());
 };
-#endif  // __has_include(<gmock/gmock.h>)
 // GCOVR_EXCL_STOP
+#endif  // __has_include(<gmock/gmock.h>)
 }  // namespace rpp_driver
 
 #endif  // PICO_DRIVER_SRC_I2S_DUPLEXSLAVEI2S_HPP_
\ No newline at end of file
diff --git a/test/test_mockadau1361.cpp b/test/test_mockadau1361.cpp
new file mode 100644
index 0000000..bb9e480
--- /dev/null
+++ b/test/test_mockadau1361.cpp
@@ -0,0 +1,34 @@
+/*
+ * Test the MockAdau1361 class.
+ * Only constructor is tested.
+ */
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+#include "adau1361.hpp"
+#include "sdkwrapper.hpp"
+
+using ::testing::_;
+class MockAdau1361Test : public ::testing::Test {
+ protected:
+  virtual void SetUp() {
+    codec_lower_ = new ::rpp_driver::MockAdau1361Lower(i2c_);
+    codec_ = new ::rpp_driver::MockAdau1361(*codec_lower_);
+  }
+
+  virtual void TearDown() {
+    delete codec_;
+    delete codec_lower_;
+  }
+
+  ::rpp_driver::MockI2cMasterInterface i2c_;
+  ::rpp_driver::MockAdau1361Lower *codec_lower_;
+  ::rpp_driver::Adau1361 *codec_;
+};  // MockAdau1361Test
+
+/*
+ * In this test case, we test teh MockAdau1361 is surely able to
+ * compile. So, none of the other methods are tested.
+ */
+TEST_F(MockAdau1361Test, Constructor) {}
\ No newline at end of file