title: Flutter - FlutterTest conflict with http.get and Mockito
body: <p>In flutter test, when using <code>mockito</code> package with testing for http service, adding</p>
  <pre><code>http.Client client
  </code></pre>
  <p>as parameters to the function is required.</p>
  <p>Instead of <code>http.get(***url***)</code>, now it is <code>client.get()</code>.</p>
  <p><code>client.get()</code> works fine with testing. However, this does not work and return error as in response.</p>