Test: add return value for mock in tests to suppress compile warning (#…

…4775)

* Test: add missing return value for mock in some tests to suppress compile warnings

* use proper data type for return values

source/module_base/module_mixing/test/mixing_test.cpp

@@ -9,6 +9,7 @@
 #define DOUBLETHRESHOLD 1e-8
 double ext_inner_product_mock(double* x1, double* x2)
 {
+    return 0.0;
 }
 class Mixing_Test : public testing::Test
 {

source/module_elecstate/test/elecstate_pw_test.cpp

@@ -104,10 +104,12 @@ void pseudopot_cell_vnl::radial_fft_q<double, base_device::DEVICE_CPU>(base_devi
 template <>
 std::complex<float>* pseudopot_cell_vnl::get_vkb_data<float>() const
 {
+    return nullptr;
 }
 template <>
 std::complex<double>* pseudopot_cell_vnl::get_vkb_data<double>() const
 {
+    return nullptr;
 }
 template <>
 void pseudopot_cell_vnl::getvnl<float, base_device::DEVICE_CPU>(base_device::DEVICE_CPU*,

source/module_io/test_serial/read_input_test.cpp

@@ -25,6 +25,7 @@ namespace GlobalFunc
 {
 bool SCAN_BEGIN(std::ifstream& ifs, const std::string& TargetName, const bool restart, const bool ifwarn)
 {
+    return false;
 }
 } // namespace GlobalFunc
 namespace Global_File