// private slot
void RHydroSimtor::Delegate::testButton_clicked()
{
   static const char* mname ("RHydroSimtor::Delegate::testButton_clicked");
   // DIAG() << mname;

   // *********************************************
   // *** (1) Open "R" Script File for Writing  ***
   // *********************************************

   const QString plugDir = UtilsNS::pluginDir();
   const QFileInfo scriptFileInfo (plugDir, "RHydroSimtor.R");
   const QString scriptPath = scriptFileInfo.absoluteFilePath();

   QFile scriptFile (scriptPath);
   const bool openOk = scriptFile.open (QIODevice::WriteOnly);
   if (!openOk)
   {
      DIAG() << mname << " ERROR Opening '" 
               << qPrintable (scriptPath) << "'";

      QApplication::beep();
      return;
   }

   // DIAG() << mname << " Opened '" << qPrintable (scriptPath) << "'";

   // *****************************************
   // *** (2) Prepare Script Response File  ***
   // *****************************************

   const QFileInfo scriptRespFileInfo (plugDir, "RHydroSimtor.out");
   const QString scriptOutPath = scriptRespFileInfo.absoluteFilePath();
   QFile scriptOutFile (scriptOutPath);
   if (scriptOutFile.exists())
   {
      const bool removeOk = scriptOutFile.remove();
      if (!removeOk)
      {
         DIAG() << mname << " ERROR Removing '"
                << qPrintable (scriptOutPath) << "'";

         QApplication::beep();
         return;
      }
   }

   // **********************************
   // *** (3) Write "R" Script File  ***
   // **********************************

   // Get Test Parameter
   const QString userInput = _testLineEdit->text();

   // Script Header Comment String
   QString headerCmtStr = "RHydroSimtor.R script. Generated: ";
   headerCmtStr += QDateTime::currentDateTime().toString();

   static const QString scriptFmt (
     "# %1\n"
     "Sys.sleep (1.5)\n"
     "resultFile <- file (\"%2\")\n"
     "resultStr <- if (\"%3\" == \"21\") \"CORRECT\" else \"INCORRECT\"\n" 
     "write (resultStr, resultFile)\n"
     "close (resultFile)\n");

   const QString scriptStr = scriptFmt .arg (headerCmtStr)
                                       .arg (scriptOutPath)
                                       .arg (userInput);

   scriptFile.write (qPrintable (scriptStr));
   scriptFile.close();

   // ****************************************
   // *** (4) Execute the "R" Script File  ***
   // ****************************************

   static const QString cmdStrFmt ("Rscript --slave %1");
   const QString cmdStr = cmdStrFmt .arg (scriptPath);

   QProcess cmdProc (this);
   cmdProc.start (cmdStr);

   bool didFinish (false);
   int waitCount (0);
   while (!didFinish && (waitCount < 30))
   {
      didFinish = cmdProc.waitForFinished (100); // milliseconds
      ++waitCount;
   }

   const QProcess::ExitStatus exStat = cmdProc.exitStatus();
   QString resultMsg ("");

   if (didFinish)
   {
      // *******************************
      // *** (5) Read Script Result  ***
      // *******************************

      const bool openOk = scriptOutFile.open (QIODevice::ReadOnly);
      if (!openOk)
      {
         resultMsg = "ERROR Result Missing '" + scriptOutPath + "'";
      }
      else
      {
         const QByteArray resultChars = scriptOutFile.readAll();
         resultMsg = QString (resultChars);
      }
   }

   else // (not didFinish)
   {
      resultMsg = "Did not finish, ExitStatus: [";
      resultMsg += QString::number ((int) exStat) + "] ";
      resultMsg += ((exStat == QProcess::NormalExit) ? "NORMAL" : "CRASH");

      cmdProc.kill();
   }

   const QString waitSecs = QString::number (waitCount / 10.0) + " secs";

   DIAG() << mname
          << "; INPUT '"  << qPrintable (userInput) << "'"
          << "; TIME: "   << qPrintable (waitSecs)
          << "; RESULT: " << qPrintable (resultMsg.trimmed());
}