Link error when trying to test a cpp11 function - c++11

Question

So I have a very simple class that contains two function and a member, this is from header file:
public:
void addMethod(std::string methodName);
std::vector<std::string> getResponse();
std::vector<std::string> methodList;
and this is definitions from source file:
std::vector<std::string> MethodsList::getResponse() {
return methodList;
}
void MethodsList::addMethod(std::string methodName)
{
methodList.push_back(methodName);
}
And i have a very basic test file just to test this :
TEST (MyTestSuit, addMethod) {
MethodsList ListOfMethods;
std::string methodName = "GetMethods";
ListOfMethods.addMethod(methodName);
ASSERT_EQ(rpcMethods.getResponse()[0], methodName);
}
But when i try to compile this i get link error as :
methods_test.cpp:(.text+0x86): undefined reference to
`MethodsList::addMethod(std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> >)'
collect2: error: ld returned 1 exit status
So at first sight it looks like the library i am using (googletest) is not compiled with c++11 support but actually i am not using precompiled library, thus i don't think it is the issue.
Here you can check some part of my CMakeList :
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14")
set(CMAKE_CXX_STANDARD 14)
set(CMAKE_CXX_EXTENSIONS OFF)
include_directories(src include)
file(GLOB SOURCE_FILES "src/*.cpp" "src/*.h")
file(GLOB PUBLIC_HEADERS "include/*.h")
add_library(${TARGET} SHARED ${SOURCE_FILES} ${PUBLIC_HEADERS})
set(TEST_FILES "${SOURCE_FILES}" "${PUBLIC_HEADERS}")
include(AddGMock)
include(AddGTestTest)
add_gmock()
add_gtest_test(API_tests ${TEST_FILES} ${TARGET})
configure_file(template-library.pc.in template-library.pc #ONLY)
...some install commands...
So how can i solve this error ? Any idea ?