test: refacor spawn[Sync]Pwd

* extract the gist into common.pwdCommand
* Merge test-child-process-buffering.js into test-child-process-stdio.js

PR-URL: https://github.com/nodejs/node/pull/22522
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

2 files changed, 15 insertions, 28 deletions

diff --git a/test/common/README.md b/test/common/README.md
index 36f3afb5c9..28d9bd04f0 100644
--- a/test/common/README.md
+++ b/test/common/README.md
@@ -317,6 +317,17 @@ A port number for tests to use if one is needed.
 
 Logs '1..0 # Skipped: ' + `msg`
 
+### pwdCommand
+* [<array>] First two argument for the `spawn`/`exec` functions.
+
+Platform normalized `pwd` command options. Usage example:
+```js
+const common = require('../common');
+const { spawn } = require('child_process');
+
+spawn(...common.pwdCommand, { stdio: ['pipe'] });
+```
+
 ### rootDir
 * [<string>]
 
@@ -350,18 +361,6 @@ was disabled at compile time.
 Skip the rest of the tests in the current file when the Node.js executable
 was compiled with a pointer size smaller than 64 bits.
 
-### spawnPwd(options)
-* `options` [<Object>]
-* return [<Object>]
-
-Platform normalizes the `pwd` command.
-
-### spawnSyncPwd(options)
-* `options` [<Object>]
-* return [<Object>]
-
-Synchronous version of `spawnPwd`.
-
 ## ArrayStream Module
 
 The `ArrayStream` module provides a simple `Stream` that pushes elements from
diff --git a/test/common/index.js b/test/common/index.js
index 18f102c5c3..6f37cb734a 100644
--- a/test/common/index.js
+++ b/test/common/index.js
@@ -26,7 +26,7 @@ const path = require('path');
 const fs = require('fs');
 const assert = require('assert');
 const os = require('os');
-const { exec, execSync, spawn, spawnSync } = require('child_process');
+const { exec, execSync, spawnSync } = require('child_process');
 const util = require('util');
 const { fixturesDir } = require('./fixtures');
 const tmpdir = require('./tmpdir');
@@ -268,22 +268,10 @@ exports.ddCommand = function(filename, kilobytes) {
 };
 
 
-exports.spawnPwd = function(options) {
-  if (exports.isWindows) {
-    return spawn('cmd.exe', ['/d', '/c', 'cd'], options);
-  } else {
-    return spawn('pwd', [], options);
-  }
-};
-
+exports.pwdCommand = exports.isWindows ?
+  ['cmd.exe', ['/d', '/c', 'cd']] :
+  ['pwd', []];
 
-exports.spawnSyncPwd = function(options) {
-  if (exports.isWindows) {
-    return spawnSync('cmd.exe', ['/d', '/c', 'cd'], options);
-  } else {
-    return spawnSync('pwd', [], options);
-  }
-};
 
 exports.platformTimeout = function(ms) {
   if (process.features.debug)