LCOV is generating coverage reports for only header files

I am using lcov and genhtml to generate code coverage reports. My unit test files only include the .h header files.

client_test.cpp

#include "gtest/gtest.h"
#include "../client.h"
...

I have noticed that the coverage report only contains coverage information for the files which were in the include section of my unit tests. Thus, the coverage report only contains the client.h files and not the client.cpp file.