test_runner: wait for stderr and stdout to complete

PR-URL: #43666 Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Antoine du Hamel <[email protected]>

Author: MoLow

lib/internal/main/test_runner.js

@@ -7,13 +7,16 @@ const{
  ArrayPrototypeSlice,
  ArrayPrototypeSort,
  Promise,
+ PromiseAll,
+ SafeArrayIterator,
  SafeSet,
 }=primordials;
 const{
  prepareMainThreadExecution,
 }=require('internal/bootstrap/pre_execution');
 const{ spawn }=require('child_process');
 const{ readdirSync, statSync }=require('fs');
+const{ finished }=require('internal/streams/end-of-stream');
 constconsole=require('internal/console/global');
 const{
 codes: {
@@ -126,9 +129,10 @@ function runTestFile(path){
 stderr+=chunk;
 });
 
-child.once('exit',(code,signal)=>{
+child.once('exit',async(code,signal)=>{
 if(code!==0||signal!==null){
 if(!err){
+awaitPromiseAll(newSafeArrayIterator([finished(child.stderr),finished(child.stdout)]));
 err=newERR_TEST_FAILURE('test failed',kSubtestsFailed);
 err.exitCode=code;
 err.signal=signal;