title: How do I append Google Test's XML output to an existing XML file?
body: <p>So Google Test allows you to write output to an XML for logging purposes and possibly for consumption by a Continuous Integration service. I want to take advantage of this facility. Apart from the regular key/value pairs the default XML output provides, the <code>RecordProperty("key", value)</code> function allows a person to append addition user-defined info to the XML output. For example, one property would be (<code>execution_time=0.56ms</code>).</p>
  
  <p>What I want to do is to get a <strong>time-series</strong> of these keys/values, that I can later plot using a plugin in a CI to visualize the execution time taken by various tests after various changes. Essentially, I want Google Test to to append to the same XML file after running each test (each test is determined by its unique timestamp / commit ID / custom parameter). Does Google Test allow you to do this?</p>
  
  <p>If Google Test does <strong>not</strong> allow to append to an existing XML file, I am thinking of using RapidXML and replicate the same structure of a Google Test report (conforming to the JUnit format). However, can a JUnit-conformant XML document consist of more than 1 <code>&lt;testsuites&gt;</code>? Since each <code>&lt;testsuites&gt;</code> is a complete test run, can I have multiple <code>&lt;testsuites&gt;</code> in the same XML document and still conform to JUnit (so that Jenkins consumes it easily?)</p>