mitigation for process hangs

pitest/src/main/java/org/pitest/mutationtest/execute/MutationTestMinion.java

@@ -100,7 +100,7 @@ public void run() {
           new TimeOutDecoratedTestSource(paramsFromParent.timeoutStrategy,
               tests, this.reporter));
 
-      this.reporter.done(ExitCode.OK);
+      repeatedlySendDoneSignal();
     } catch (final Throwable ex) {
       ex.printStackTrace(System.out);
       LOG.log(Level.WARNING, "Error during mutation test", ex);
@@ -109,6 +109,17 @@ public void run() {
 
   }
 
+  private void repeatedlySendDoneSignal() throws InterruptedException {
+    // there have been reports of the done signal getting lost, causing the main process
+    // to hang. The root cause of this issue has not been found, this attempts to mitigate it
+    // by resending the signal. We don't want to spend too long doing this, as it is better for
+    // the minion to end naturally, than be killed by the main process.
+    for (int i = 0; i != 10; i++) {
+      this.reporter.done(ExitCode.OK);
+      Thread.sleep(100);
+    }
+  }
+
   private void configureVerbosity(MinionArguments paramsFromParent) {
     Log.setVerbose(paramsFromParent.verbosity());
     if (!paramsFromParent.verbosity().showMinionOutput()) {

pitest/src/test/java/org/pitest/mutationtest/execute/MutationTestMinionTest.java

@@ -1,6 +1,7 @@
 package org.pitest.mutationtest.execute;
 
 import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.atLeastOnce;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 import static org.pitest.mutationtest.LocationMother.aMutationId;
@@ -85,7 +86,7 @@ public void setup() {
   @Test
   public void shouldReportNoErrorWhenNoMutationsSupplied() {
     this.testee.run();
-    verify(this.reporter).done(ExitCode.OK);
+    verify(this.reporter, atLeastOnce()).done(ExitCode.OK);
   }
 
   @Test