tests.js

Promise.all(logSources.map(logSource => {
  logSource.popAsync().then(log => {
    minheap.insert({
      ts: log.date.getTime(),
      source: i,
      data: log
    })
  });
}).then(
  while (minheap.heapList.length) {
    let heapNode = minheap.popMin();
    let currTimestamp = heapNode['ts'];
    printer.print(heapNode.data);
    let nextMinTimestamp = minheap.getPeakTimestamp();
    while (currTimestamp <= nextMinTimestamp) {
      logSources[heapNode['source']].popAsync().then(log => {
        if (log) {
          let logtime = log.date.getTime();
          if (logtime <= nextMinTimestamp) {
            printer.print(log);
            currTimestamp = logtime;
          } else {
            minheap.insert({
              ts: logtime,
              source: heapNode["source"],
              data: log
            });

            break;
          }
        }
      });
    }
  }
));