title: Flink Unit Test over ProcessWindowFunction<IN, OUT, KEY, W>
body: <p>How can I create a unit test for a Stateful Process Function. I have something like this:</p>
  <pre><code> private static SingleOutputStreamOperator&lt;Tuple&gt; methodName(KeyedStream&lt;Event, String&gt; stream) {
          return stream.window(TumblingEventTimeWindows.of(Time.minutes(10)))
                  .process(new ProcessFunction());
      }
  </code></pre>
  <p>and</p>
  <pre><code>ProcessFunction extends ProcessWindowFunction&lt;IN, OUT, KEY, W&gt;
  </code></pre>
  <p>All the Harness tests that I've found in Flink page are extending from KeyedProcessFunction and this is not my case.
  Thanks.
  Kind regards!</p>