test: refactor common.ddCommand()

* Remove different paths for Windows and POSIX.
* Remove fixtures file. Simply run the command immediately/directly.
* Since it is never called with more than one value for kilobytes,
  eliminate that argument.
* Update/simplify tests that use this function. (They no longer need to
  use child_process to run the command.)
* Update documentation.

Backport-PR-URL: #23630
PR-URL: #23411
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: George Adams <george.adams@uk.ibm.com>

test/common/README.md

@@ -52,10 +52,9 @@ symlinks
 ([SeCreateSymbolicLinkPrivilege](https://msdn.microsoft.com/en-us/library/windows/desktop/bb530716(v=vs.85).aspx)).
 On non-Windows platforms, this always returns `true`.
 
-### ddCommand(filename, kilobytes)
-* return [<Object>]
+### ddCommand(filename)
 
-Platform normalizes the `dd` command
+Creates a 10 MB file of all null characters.
 
 ### disableCrashOnUnhandledRejection()
 

test/common/index.js

@@ -29,7 +29,6 @@ const os = require('os');
 const { exec, execSync, spawnSync } = require('child_process');
 const util = require('util');
 const Timer = process.binding('timer_wrap').Timer;
-const { fixturesDir } = require('./fixtures');
 const tmpdir = require('./tmpdir');
 const {
   bits,
@@ -174,13 +173,10 @@ function childShouldThrowAndAbort() {
   });
 }
 
-function ddCommand(filename, kilobytes) {
-  if (isWindows) {
-    const p = path.resolve(fixturesDir, 'create-file.js');
-    return `"${process.argv[0]}" "${p}" "${filename}" ${kilobytes * 1024}`;
-  } else {
-    return `dd if=/dev/zero of="${filename}" bs=1024 count=${kilobytes}`;
-  }
+function ddCommand(filename) {
+  const fd = fs.openSync(filename, 'w');
+  fs.ftruncateSync(fd, 10 * 1024 * 1024);
+  fs.closeSync(fd);
 }
 
 

test/parallel/test-fs-error-messages.js

@@ -31,7 +31,7 @@ tmpdir.refresh();
 const nonexistentFile = fixtures.path('non-existent');
 const nonexistentDir = fixtures.path('non-existent', 'foo', 'bar');
 const existingFile = fixtures.path('exit.js');
-const existingFile2 = fixtures.path('create-file.js');
+const existingFile2 = fixtures.path('a.js');
 const existingDir = tmpdir.path;
 const existingDir2 = fixtures.path('keys');
 const { COPYFILE_EXCL } = fs.constants;

test/parallel/test-http-chunk-problem.js

@@ -63,34 +63,31 @@ function executeRequest(cb) {
 
 tmpdir.refresh();
 
-const ddcmd = common.ddCommand(filename, 10240);
+common.ddCommand(filename);
 
-cp.exec(ddcmd, function(err, stdout, stderr) {
-  assert.ifError(err);
-  server = http.createServer(function(req, res) {
-    res.writeHead(200);
+server = http.createServer(function(req, res) {
+  res.writeHead(200);
 
-    // Create the subprocess
-    const cat = cp.spawn('cat', [filename]);
+  // Create the subprocess
+  const cat = cp.spawn('cat', [filename]);
 
-    // Stream the data through to the response as binary chunks
-    cat.stdout.on('data', (data) => {
-      res.write(data);
-    });
-
-    cat.stdout.on('end', () => res.end());
+  // Stream the data through to the response as binary chunks
+  cat.stdout.on('data', (data) => {
+    res.write(data);
+  });
 
-    // End the response on exit (and log errors)
-    cat.on('exit', (code) => {
-      if (code !== 0) {
-        console.error(`subprocess exited with code ${code}`);
-        process.exit(1);
-      }
-    });
+  cat.stdout.on('end', () => res.end());
 
+  // End the response on exit (and log errors)
+  cat.on('exit', (code) => {
+    if (code !== 0) {
+      console.error(`subprocess exited with code ${code}`);
+      process.exit(1);
+    }
   });
 
-  server.listen(0, () => {
-    executeRequest(() => server.close());
-  });
+});
+
+server.listen(0, () => {
+  executeRequest(() => server.close());
 });

test/parallel/test-pipe-file-to-http.js

@@ -25,7 +25,6 @@ const assert = require('assert');
 const fs = require('fs');
 const http = require('http');
 const path = require('path');
-const cp = require('child_process');
 
 const tmpdir = require('../common/tmpdir');
 tmpdir.refresh();
@@ -57,12 +56,8 @@ const server = http.createServer(function(req, res) {
 server.listen(0);
 
 server.on('listening', function() {
-  const cmd = common.ddCommand(filename, 10240);
-
-  cp.exec(cmd, function(err) {
-    assert.ifError(err);
-    makeRequest();
-  });
+  common.ddCommand(filename);
+  makeRequest();
 });
 
 function makeRequest() {

test/sequential/test-module-loading.js

@@ -251,7 +251,6 @@ try {
 
   assert.deepStrictEqual(children, {
     'common/index.js': {
-      'common/fixtures.js': {},
       'common/tmpdir.js': {}
     },
     'fixtures/not-main-module.js': {},