Install Google Test and Google Mock on Ubuntu

CMakeLists.txt

cmake_minimum_required(VERSION 3.5)

project(example LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(GTest REQUIRED)
include_directories(${GTEST_INCLUDE_DIRS})

add_executable(example main.cpp)
target_link_libraries(example ${GTEST_LIBRARIES} ${GTEST_MAIN_LIBRARIES})

install_gtest_gmock.sh

cd ~
git clone https://github.com/google/googletest.git
cd googletest
mkdir build && cd build
cmake .. -DBUILD_SHARED_LIBS=ON -DINSTALL_GTEST=ON -DCMAKE_INSTALL_PREFIX:PATH=/usr
make -j8
sudo make install
sudo ldconfig

main.cpp

#include <gtest/gtest.h>

TEST(test_case, example_test)
{
    EXPECT_EQ(2, 2);
}

int main(int argc, char **argv)
{
    testing::InitGoogleTest(&argc, argv);
    return RUN_ALL_TESTS();
}

Never specify -DCMAKE_INSTALL_PREFIX:PATH=/usr, unless you want to break your system, as it will inevitably lead to conflicts with files managed by the system package manager (like apt). The default CMake install prefix, /usr/local, sidesteps this issue by installing files in a separate directory hierarchy - this is still less ideal than installing libgtest-dev and libgmock-dev with apt, but won't break your system. Generally speaking, never override defaults unless you really know what you're doing!