cmake successful

make produces following:
[ 99%] Built target plasmanetworkmanagement_vpncui
/usr/bin/ld: CMakeFiles/mobileproviderstest.dir/mobileproviderstest.cpp.o: in function `MobileProvidersTest::testProviders()':
mobileproviderstest.cpp:(.text+0x23d0): undefined reference to `MobileProviders::MobileProviders()'
/usr/bin/ld: mobileproviderstest.cpp:(.text+0x23fc): undefined reference to `MobileProviders::getProvidersList(QString, NetworkManager::ConnectionSettings::ConnectionType)'
/usr/bin/ld: mobileproviderstest.cpp:(.text+0x24a1): undefined reference to `MobileProviders::getApns(QString const&)'
/usr/bin/ld: mobileproviderstest.cpp:(.text+0x2514): undefined reference to `MobileProviders::getApnInfo(QString const&)'
/usr/bin/ld: mobileproviderstest.cpp:(.text+0x25e6): undefined reference to `MobileProviders::~MobileProviders()'
/usr/bin/ld: CMakeFiles/mobileproviderstest.dir/mobileproviderstest.cpp.o: in function `MobileProvidersTest::testProviderFromMccMnc()':
mobileproviderstest.cpp:(.text+0x2680): undefined reference to `MobileProviders::MobileProviders()'
/usr/bin/ld: mobileproviderstest.cpp:(.text+0x2697): undefined reference to `MobileProviders::getProvidersFromMCCMNC(QString const&)'
/usr/bin/ld: mobileproviderstest.cpp:(.text+0x26ef): undefined reference to `MobileProviders::~MobileProviders()'
collect2: error: ld returned 1 exit status
make[2]: *** [tests/CMakeFiles/mobileproviderstest.dir/build.make:118: bin/mobileproviderstest] Error 1
make[1]: *** [CMakeFiles/Makefile2:2125: tests/CMakeFiles/mobileproviderstest.dir/all] Error 2
make: *** [Makefile:160: all] Error 2

SOFTWARE/OS VERSIONS
Operating System: Kubuntu 21.04
KDE Plasma Version: 5.22.5
KDE Frameworks Version: 5.86.0
Qt Version: 5.15.2
Kernel Version: 5.11.0-36-generic (64-bit)
Graphics Platform: X11