title: What causes maven-javadoc-plugin goal test-javadoc to fail on errors but test-javadoc-no-fork just to have warnings
body: <p>I have a Maven project with maven-javadoc-plugin and JDK8. When I run <code>mvn javadoc:test-javadoc</code> then the plugin reports documentation-errors and stops, but when I run <code>mvn javadoc:test-javadoc-no-fork</code> the plugin runs successful and there's just some warnings.</p>
  
  <p>The question is <strong>NOT</strong> how to fix or the documentation-errors. The plugin spotted real documentation-issues, that need to be fixed, so the reported errors of <code>mvn javadoc:test-javadoc</code> are the correct result.</p>
  
  <p>The question is: <strong>Why does <code>mvn javadoc:test-javadoc-no-fork</code> not fail but handle the issues just as warning?</strong></p>
  
  <hr>
  
  <p>Background:</p>
  
  <ul>
  <li>the project is a multi-module-project</li>
  <li>Maven version: 3.3.9</li>
  <li>maven-javadoc-plugin: 2.9.4 (the same behaviour occurs for 3.0.0-M1)</li>
  <li>Java8</li>
  </ul>
  
  <hr>
  
  <p>The sported problem in <code>TracingServiceSpringTest</code> has really a missing documentation for the thrown <code>DatatypeConfigurationException</code></p>
  
  <pre><code>/** scenario: some text... **/
  @Test
  public void testImport() throws DatatypeConfigurationException {...
  </code></pre>
  
  <hr>
  
  <p>Output when running <code>mvn javadoc:test-javadoc</code></p>
  
  <pre><code>[INFO]
  [INFO] &lt;&lt;&lt; maven-javadoc-plugin:2.10.4:test-javadoc (default-cli) &lt; generate-test-sources @ agrovet-server &lt;&lt;&lt;
  [INFO]
  [INFO] --- maven-javadoc-plugin:2.10.4:test-javadoc (default-cli) @ agrovet-server ---
  [INFO]
  ...
  3 errors
  9 warnings
  [INFO] ------------------------------------------------------------------------
  [INFO] Reactor Summary:
  [INFO]
  [INFO] PROJECT ............................................ SUCCESS [  1.131 s]
  [INFO] PROJECT :: Client .................................. SUCCESS [ 43.908 s]
  [INFO] PROJECT :: Server .................................. FAILURE [ 44.774 s]
  [INFO] ------------------------------------------------------------------------
  [INFO] BUILD FAILURE
  [INFO] ------------------------------------------------------------------------
  [INFO] Total time: 01:36 min
  [INFO] Finished at: 2017-09-23T21:33:33+02:00
  [INFO] Final Memory: 96M/1573M
  [INFO] ------------------------------------------------------------------------
  [ERROR] Failed to execute goal org.apache.maven.plugins:maven-javadoc-plugin:2.10.4:test-javadoc (default-cli) on project PROJECT-server: An error has occurred in Test JavaDocs report generation:
  [ERROR] Exit code: 1 - F:\workspaces\PROJECT\PROJECT-server\src\test\java\com\example\PROJECT\infrastructure\TracingServiceSpringTest.java:389: warning:
  no @throws for javax.xml.datatype.DatatypeConfigurationException
  [ERROR] public void testImport() throws DatatypeConfigurationException {
  [ERROR] ^
  ...
  [ERROR]
  [ERROR] Command line was: "C:\Program Files\Java\jdk1.8.0_121\jre\..\bin\javadoc.exe" @options @packages
  [ERROR]
  [ERROR] Refer to the generated Javadoc files in 'F:\workspaces\PROJECT\PROJECT-server\target\site\testapidocs' dir.
  [ERROR] -&gt; [Help 1]
  [ERROR]
  
  ...
  </code></pre>
  
  <hr>
  
  <p>Output when running <code>mvn javadoc:test-javadoc-no-fork</code></p>
  
  <pre><code>8 warnings
  [WARNING] Javadoc Warnings
  [WARNING] F:\workspaces\PROJECT\PROJECT-server\src\test\java\com\example\PROJECT\infrastructure\TracingServiceSpringTest:389: warning: no @throws for javax.xml.datatype.DatatypeConfigurationException
  [WARNING] public void testImport() throws DatatypeConfigurationException {
  [WARNING] ^
  ...
  [INFO] ------------------------------------------------------------------------
  [INFO] Reactor Summary:
  [INFO] 
  [INFO] PROJECT ............................................ SUCCESS [  0.454 s]
  [INFO] PROJECT :: Client .................................. SUCCESS [  0.011 s]
  [INFO] PROJECT :: Server .................................. SUCCESS [  6.763 [INFO] ------------------------------------------------------------------------
  [INFO] BUILD SUCCESS
  [INFO] ------------------------------------------------------------------------
  ...
  </code></pre>
  
  <hr>
  
  <p>Relevant POM Parts, parent <code>pom.xml</code> (the complete pom is just too huge, but this is the only part that mentions the <code>maven-javadoc-plugin</code> :</p>
  
  <pre><code>&lt;dependencyManagement&gt;
      &lt;dependencies&gt;
          ...
          &lt;plugin&gt;
              &lt;groupId&gt;org.apache.maven.plugins&lt;/groupId&gt;
              &lt;artifactId&gt;maven-javadoc-plugin&lt;/artifactId&gt;
              &lt;version&gt;2.10.4&lt;/version&gt;
          &lt;/plugin&gt;
      &lt;/dependencies&gt;
  &lt;/dependencyManagement&gt;
  ...
  &lt;reporting&gt;
      &lt;plugins&gt;
          ...
          &lt;plugin&gt;
              &lt;groupId&gt;org.apache.maven.plugins&lt;/groupId&gt;
              &lt;artifactId&gt;maven-javadoc-plugin&lt;/artifactId&gt;
              &lt;reportSets&gt;
                  &lt;reportSet&gt;
                      &lt;reports&gt;
                          &lt;!-- 
                          javadoc-no-fork in order to prevent JavaDoc process from runing generate-source again
                          but this also requries that JavaDoc generation runs after compile: "mvn install site"
                          but not on a black project "mvn clean site"
                          --&gt;
                          &lt;report&gt;javadoc-no-fork&lt;/report&gt;
                          &lt;report&gt;test-javadoc-no-fork&lt;/report&gt;
                      &lt;/reports&gt;
                  &lt;/reportSet&gt;
              &lt;/reportSets&gt;
          &lt;/plugin&gt;
      &lt;/plugins&gt;
  &lt;/reporting&gt;
  </code></pre>