Make printExitInfoTimingTable method private and test indirectly

With this change we can be sure that the 'logger' is defined.
Increases coverage on Node.js 12.

src/flow-control/log-timings.spec.ts

@@ -109,20 +109,14 @@ it('does not log timings summary if there was an error', () => {
 });
 
 it('logs the sorted timings summary when all processes close successfully', () => {
-    jest.spyOn(controller, 'printExitInfoTimingTable');
     controller.handle(commands);
 
     commands[0].close.next(command0ExitInfo);
     commands[1].close.next(command1ExitInfo);
 
+    expect(logger.logGlobalEvent).toHaveBeenCalledTimes(1);
+    expect(logger.logGlobalEvent).toHaveBeenCalledWith('Timings:');
     expect(logger.logTable).toHaveBeenCalledTimes(1);
-
-    // un-sorted ie by finish order
-    expect(controller.printExitInfoTimingTable).toHaveBeenCalledWith([
-        command0ExitInfo,
-        command1ExitInfo,
-    ]);
-
     // sorted by duration
     expect(logger.logTable).toHaveBeenCalledWith([
         LogTimings.mapCloseEventToTimingInfo(command1ExitInfo),

src/flow-control/log-timings.ts

@@ -51,15 +51,15 @@ export class LogTimings implements FlowController {
         this.timestampFormat = timestampFormat;
     }
 
-    printExitInfoTimingTable(exitInfos: CloseEvent[]) {
+    private printExitInfoTimingTable(exitInfos: CloseEvent[]) {
         const exitInfoTable = _(exitInfos)
             .sortBy(({ timings }) => timings.durationSeconds)
             .reverse()
             .map(LogTimings.mapCloseEventToTimingInfo)
             .value();
 
-        this.logger?.logGlobalEvent('Timings:');
-        this.logger?.logTable(exitInfoTable);
+        this.logger.logGlobalEvent('Timings:');
+        this.logger.logTable(exitInfoTable);
         return exitInfos;
     }
 
@@ -73,14 +73,14 @@ export class LogTimings implements FlowController {
             command.timer.subscribe(({ startDate, endDate }) => {
                 if (!endDate) {
                     const formattedStartDate = formatDate(startDate, this.timestampFormat);
-                    this.logger?.logCommandEvent(
+                    this.logger.logCommandEvent(
                         `${command.command} started at ${formattedStartDate}`,
                         command
                     );
                 } else {
                     const durationMs = endDate.getTime() - startDate.getTime();
                     const formattedEndDate = formatDate(endDate, this.timestampFormat);
-                    this.logger?.logCommandEvent(
+                    this.logger.logCommandEvent(
                         `${
                             command.command
                         } stopped at ${formattedEndDate} after ${durationMs.toLocaleString()}ms`,