title: Maven runs unit tests twice with clover plugin
body: <p>I have this plugin code in my pom.xml. If I remove this plugin then Maven won't run unit tests twice. I just wanted to know which part of this plugin makes the unit tests run twice. </p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;plugin&gt;
      &lt;groupId&gt;com.atlassian.maven.plugins&lt;/groupId&gt;
      &lt;artifactId&gt;maven-clover2-plugin&lt;/artifactId&gt;
      &lt;version&gt;3.0.4&lt;/version&gt;
      &lt;configuration&gt;
          &lt;licenseLocation&gt;/location/to/clover.license&lt;/licenseLocation&gt;
          &lt;generateXml&gt;true&lt;/generateXml&gt;
          &lt;generateHtml&gt;true&lt;/generateHtml&gt;
      &lt;/configuration&gt;
      &lt;executions&gt;
          &lt;execution&gt;
              &lt;phase&gt;generate-sources&lt;/phase&gt;
              &lt;goals&gt;
                  &lt;goal&gt;instrument&lt;/goal&gt;
              &lt;/goals&gt;
          &lt;/execution&gt;
          &lt;execution&gt;
              &lt;id&gt;main&lt;/id&gt;
              &lt;phase&gt;verify&lt;/phase&gt;
              &lt;goals&gt;
                  &lt;goal&gt;instrument&lt;/goal&gt;
                  &lt;goal&gt;aggregate&lt;/goal&gt;
                  &lt;goal&gt;clover&lt;/goal&gt;
              &lt;/goals&gt;
          &lt;/execution&gt;
          &lt;execution&gt;
              &lt;id&gt;site&lt;/id&gt;
              &lt;phase&gt;pre-site&lt;/phase&gt;
              &lt;goals&gt;
                  &lt;goal&gt;instrument&lt;/goal&gt;
                  &lt;goal&gt;aggregate&lt;/goal&gt;
              &lt;/goals&gt;
          &lt;/execution&gt;
      &lt;/executions&gt;
  &lt;/plugin&gt;
  </code></pre>