diff --git a/trunk/src/utest/srs_utest_kernel.cpp b/trunk/src/utest/srs_utest_kernel.cpp
index 51fd94972..9ac6641a1 100644
--- a/trunk/src/utest/srs_utest_kernel.cpp
+++ b/trunk/src/utest/srs_utest_kernel.cpp
@@ -197,6 +197,29 @@ srs_error_t MockBufferReader::read(void* buf, size_t size, ssize_t* nread)
     return srs_success;
 }
 
+MockSrsCodec::MockSrsCodec()
+{
+}
+
+MockSrsCodec::~MockSrsCodec()
+{
+}
+
+int MockSrsCodec::nb_bytes()
+{
+    return 0;
+}
+
+srs_error_t MockSrsCodec::encode(SrsBuffer* /*buf*/)
+{
+    return srs_success;
+}
+
+srs_error_t MockSrsCodec::decode(SrsBuffer* /*buf*/)
+{
+    return srs_success;
+}
+
 #ifdef ENABLE_UTEST_KERNEL
 
 VOID TEST(KernelBufferTest, DefaultObject)
@@ -1350,6 +1373,26 @@ VOID TEST(KernelStreamTest, StreamWriteBytes)
     EXPECT_EQ(0x19, s.read_1bytes());
 }
 
+VOID TEST(KernelBufferTest, CoverAll)
+{
+    if (true) {
+        MockSrsCodec codec;
+        EXPECT_TRUE(0 == codec.nb_bytes());
+        EXPECT_TRUE(srs_success == codec.encode(NULL));
+        EXPECT_TRUE(srs_success == codec.decode(NULL));
+    }
+    
+    if (true) {
+        SrsBuffer buf((char*)"hello", 5);
+        EXPECT_EQ(5, buf.size());
+        EXPECT_EQ(5, buf.left());
+        
+        buf.read_1bytes();
+        EXPECT_EQ(5, buf.size());
+        EXPECT_EQ(4, buf.left());
+    }
+}
+
 /**
 * test the kernel utility, time
 */
diff --git a/trunk/src/utest/srs_utest_kernel.hpp b/trunk/src/utest/srs_utest_kernel.hpp
index ad8bb197c..d931fb88d 100644
--- a/trunk/src/utest/srs_utest_kernel.hpp
+++ b/trunk/src/utest/srs_utest_kernel.hpp
@@ -31,6 +31,7 @@ CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 #include <string>
 #include <srs_kernel_file.hpp>
+#include <srs_kernel_buffer.hpp>
 #include <srs_protocol_stream.hpp>
 
 class MockBufferReader: public ISrsReader
@@ -93,5 +94,16 @@ public:
     void mock_reset_offset();
 };
 
+class MockSrsCodec : public ISrsCodec
+{
+public:
+    MockSrsCodec();
+    virtual ~MockSrsCodec();
+public:
+    virtual int nb_bytes();
+    virtual srs_error_t encode(SrsBuffer* buf);
+    virtual srs_error_t decode(SrsBuffer* buf);
+};
+
 #endif