test: capture stderr from child processes

If the test fails with errors from the child commands, there is no debug info. Suppliment the stderr data so that we know what to look for. Refs: #25988 PR-URL: #26007 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Author: gireeshpunathil

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

@@ -33,19 +33,17 @@ const MB = KB * KB;
  grep = spawn('grep', ['x'], { stdio: [cat.stdout, 'pipe', 'pipe'] });
  wc = spawn('wc', ['-c'], { stdio: [grep.stdout, 'pipe', 'pipe'] });
 
+ [cat, grep, wc].forEach((child, index) => {
+ child.stderr.on('data', (d) => {
+ // 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);
+ }));
+ });
+
  wc.stdout.on('data', common.mustCall(function(data) {
  assert.strictEqual(data.toString().trim(), MB.toString());
  }));
-
- cat.on('exit', common.mustCall(function(code) {
- assert.strictEqual(code, 0);
- }));
-
- grep.on('exit', common.mustCall(function(code) {
- assert.strictEqual(code, 0);
- }));
-
- wc.on('exit', common.mustCall(function(code) {
- assert.strictEqual(code, 0);
- }));
 }