title: Gtest file not found by g++
body: <p>I run a code which needs <code>gtest</code>, but terminal shows:</p>
  
  <blockquote>
    <p>'gtest/gtest.h' file not found</p>
  </blockquote>
  
  <p>Here is the command:</p>
  
  <pre><code>$ g++ -w -I ../gtest/include/gtest -I../snap-core -I../glib-core -c run-all-tests.cpp
  </code></pre>
  
  <p>I think I add the path of <code>gtest</code>, but system did not find it.</p>