test: increase debugging information on failure

Increase the information displayed when
test-child-process-pipe-dataflow.js fails.
PR-URL: #27790
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

Author: Trott

test/parallel/test-child-process-pipe-dataflow.js

@@ -38,16 +38,19 @@ const MB = KB * KB;
 grep.stdout._handle.readStart=common.mustNotCall();
 
 [cat,grep,wc].forEach((child,index)=>{
-child.stderr.on('data',(d)=>{
+consterrorHandler=(thing,type)=>{
 // Don't want to assert here, as we might miss error code info.
-console.error(`got unexpected data from child #${index}:\n${d}`);
-});
-child.on('exit',common.mustCall(function(code){
-assert.strictEqual(code,0);
+console.error(`unexpected ${type} from child #${index}:\n${thing}`);
+};
+
+child.stderr.on('data',(d)=>{errorHandler(d,'data');});
+child.on('error',(err)=>{errorHandler(err,'error');});
+child.on('exit',common.mustCall((code)=>{
+assert.strictEqual(code,0,`child ${index} exited with code ${code}`);
 }));
 });
 
-wc.stdout.on('data',common.mustCall(function(data){
+wc.stdout.on('data',common.mustCall((data)=>{
 assert.strictEqual(data.toString().trim(),MB.toString());
 }));
 }