title: What is the difference between gtest and gmock?
body: <p>I'm trying to understand the purpose of <code>google-mock</code>, <a href="https://github.com/google/googletest/blob/master/googlemock/README.md" rel="noreferrer">Google's C++ mocking framework</a>.</p>
  
  <p>I have already worked with <code>gtest</code> earlier, but still I can't understand what <code>gmock</code> is. Why do we need it?</p>
  
  <p><code>gtest</code> is used for unit testing. What do we need <code>gmock</code> for then, if <code>gmock</code> is required for <code>unit testing</code>?</p>