CMake linking GoogleTest and UnitTests
<p>Im trying to setup GoogleTest to add some test on a Legacy-Code base.</p>

<p>So i downloaded the latest verson of GoogleTest and extracted it side by side to the legacy code and added an simple test to verify, that the installation/configuration is correct.</p>

<p>Every time i try to make the Project with CMake i end up with the following error:</p>

<pre><code>Scanning dependencies of target RunUnitTests
[ 92%] Building CXX object Testing_Code/CMakeFiles/RunUnitTests.dir/test_main.cpp.o
Linking CXX executable RunUnitTests
CMakeFiles/RunUnitTests.dir/test_main.cpp.o: In function `main':
test_main.cpp:(.text+0x1b): undefined reference to `testing::InitGoogleTest(int*, char**)'
CMakeFiles/RunUnitTests.dir/test_main.cpp.o: In function `RUN_ALL_TESTS()':
test_main.cpp:(.text._Z13RUN_ALL_TESTSv[_Z13RUN_ALL_TESTSv]+0x7): undefined reference to `testing::UnitTest::GetInstance()'
test_main.cpp:(.text._Z13RUN_ALL_TESTSv[_Z13RUN_ALL_TESTSv]+0x10): undefined reference to `testing::UnitTest::Run()'
collect2: error: ld returned 1 exit status
Testing_Code/CMakeFiles/RunUnitTests.dir/build.make:85: recipe for target 'Testing_Code/RunUnitTests' failed
make[2]: *** [Testing_Code/RunUnitTests] Error 1
CMakeFiles/Makefile2:429: recipe for target 'Testing_Code/CMakeFiles/RunUnitTests.dir/all' failed
make[1]: *** [Testing_Code/CMakeFiles/RunUnitTests.dir/all] Error 2
Makefile:116: recipe for target 'all' failed
make: *** [all] Error 2
</code></pre>

<p>(full output visible <a href="https://gist.github.com/cedi/9203d899f66e367757c5" rel="nofollow">here</a>)</p>

<p>Iv'e been searching for a fix for a long time. I have googled and read so many links at the internet that i lost the overview.
Im really new to CMake and think i miss something small but major...</p>

<p>My folder-hierarchy looks like the following:</p>

<pre><code>+
|-+CMake
| |-run.sh
| |-BuildAll.sh
| |-CMakeLists.txt
|
|-+cpp-project
| |-CMakeLists.txt
| |-+work
| | |-CMakeLists.txt
| | 
| |-+include
|   |-CMakeLists.txt
|
|-+GoogleTest
| |-CMakeLists.txt
| |-+googlemock
| |-+googletest
| |-RADME.md
| |-travis.sh
|
|-+Testing_Code
  |-CMakeLists.txt
  |-+test
    |-CMakeLists.txt
    |-test.
</code></pre>

<p>To start the compiling i run <code>sh ~/code/CMake/run.sh</code> which looks like the following:</p>

<pre><code>cp BuildAll.sh ./../BuildAll.sh
cp CMakeLists.txt ./../CMakeLists.txt
cd ..
sh BuildAll.sh $1
</code></pre>

<p>And BuildAll does some cleaning-stuff and generate some folders, etc.:</p>

<pre><code>#!/bin/bash

alwaysCleanBuild=$1
control="control"
unittest_out="$control/test"
build="build"
include="$build/include"

if [ $alwaysCleanBuild = true ]; then
    if [ -d "$control" ]; then
        rm -r "$control"
    fi

    if [ -d "$build" ]; then
        rm -r "$build"
    fi
fi

mkdir $control
mkdir $build
mkdir $include

cd $build

cp -r ../GoogleTest/googletest/include/* ./include/
cp ../cpp-project/include/* ./include

cmake ..

if [ $? = 0 ]; then
    make

    if [ $? = 0 ]; then
            ./../control/RunUnitTests
    fi
fi
</code></pre>

<p>New Folders in short:</p>

<ul>
<li><code>control</code> is the output dir of the cpp-project libs/binarys/what ever you like to call the output ;)</li>
<li><code>build</code> is the CMake destination for generating the Makefile, etc.</li>
<li><code>build\include</code> is the public include-dir for the tests to access gtest and cpp-projects headders.</li>
</ul>

<p>The CMake/CMakeLists.txt is copyed from the <code>BuildAll.sh</code> Script to the root-directory. So there is a 'root'-<code>CMakeLists.txt</code>. This CMakeLists specifies the <code>include_directories</code> and the output-directory('s):</p>

<pre><code>cmake_minimum_required(VERSION 3.2)

project(Test)

set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/../control)
set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/../control)
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/../control)

include_directories(${CMAKE_BINARY_DIR}/include)

add_subdirectory(cpp-project)
add_subdirectory(GoogleTest)
add_subdirectory(Testing_Code)
</code></pre>

<p>GoogleTest's CMakeLists are all untouched and they are running like a charm.
The cpp-projects CMakeFile are running very fine too and they output everything to the <code>control</code> directory. (I'm really satisfied with CMake. It's much quicker and simpler than the plain old Makefiles (in my oppinion) for the 'easy-beginner-steps').</p>

<p>The CMakeLists from <code>/Testing_Code/</code> also looks verry simple, but i think in there you will find my mistake:</p>

<pre><code>cmake_minimum_required(VERSION 3.2)

project(Testing)

# Create main.cpp which uses gtest
file(WRITE test_main.cpp "#include &lt;gtest/gtest.h&gt;\n\n")
file(APPEND test_main.cpp "int main(int argc, char **argv)\n{\n")
file(APPEND test_main.cpp "    testing::InitGoogleTest(&amp;argc, argv);\n")
file(APPEND test_main.cpp "    return RUN_ALL_TESTS();\n")
file(APPEND test_main.cpp "}\n")

# build all tests
ADD_SUBDIRECTORY(test)
# ADD_SUBDIRECTORY(test_2)
# ADD_SUBDIRECTORY(test_3)

# build the test_main
ADD_EXECUTABLE(RunUnitTests test_main.cpp ${GTEST_INCLUDE})

# Link RunUnitTests with GoogleTest and cpp-project
TARGET_LINK_LIBRARIES(RunUnitTests ${GoogleTest} ${cpp-project})
</code></pre>

<p>I can't find the mistake in here and i really hope that someone could help me with this.</p>