Document that tests *must* be executed in a forked VM with Maven
as otherwise the `javaagent` is not set and no execution data
will be recorded.
diff --git a/org.jacoco.doc/docroot/doc/maven.html b/org.jacoco.doc/docroot/doc/maven.html
index 99673e3..8e786c5 100644
--- a/org.jacoco.doc/docroot/doc/maven.html
+++ b/org.jacoco.doc/docroot/doc/maven.html
@@ -31,6 +31,16 @@
be compiled with debug information.
</p>
+<p class="hint">
+ When using the <tt>maven-surefire-plugin</tt> or <tt>maven-failsafe-plugin</tt>
+ you <b>must not</b> use a
+ <a href="http://maven.apache.org/surefire/maven-surefire-plugin/test-mojo.html#forkCount">
+ <tt>forkCount</tt></a> of <tt>0</tt> or set the
+ <a href="http://maven.apache.org/surefire/maven-surefire-plugin/test-mojo.html#forkMode">
+ <tt>forkMode</tt></a> to <tt>never</tt> as this would prevent the execution of
+ the tests with the <tt>javaagent</tt> set and no coverage would be recorded.
+</p>
+
<h2>Example</h2>
<ul>