test: refactor test-init.js

1. Lot of repeating code has been refactored to a function
2. Errors in async calls are properly asserted
3. Fail the test if the callbacks are not fired

PR-URL: https://github.com/nodejs/node/pull/10384
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Julian Duque <julianduquej@gmail.com>

test/sequential/test-init.js

@@ -2,46 +2,40 @@
 const common = require('../common');
 const assert = require('assert');
 const child = require('child_process');
-const util = require('util');
+const path = require('path');
+
 if (process.env['TEST_INIT']) {
-  util.print('Loaded successfully!');
-} else {
-  // change CWD as we do this test so its not dependant on current CWD
-  // being in the test folder
-  process.chdir(__dirname);
+  return process.stdout.write('Loaded successfully!');
+}
+
+process.env.TEST_INIT = 1;
 
-  // slow but simple
-  var envCopy = JSON.parse(JSON.stringify(process.env));
-  envCopy.TEST_INIT = 1;
+function test(file, expected) {
+  const path = `"${process.execPath}" ${file}`;
+  child.exec(path, {env: process.env}, common.mustCall((err, out) => {
+    assert.ifError(err);
+    assert.strictEqual(out, expected, `'node ${file}' failed!`);
+  }));
+}
 
-  child.exec('"' + process.execPath + '" test-init', {env: envCopy},
-      function(err, stdout, stderr) {
-        assert.equal(stdout, 'Loaded successfully!',
-                     '`node test-init` failed!');
-      });
-  child.exec('"' + process.execPath + '" test-init.js', {env: envCopy},
-      function(err, stdout, stderr) {
-        assert.equal(stdout, 'Loaded successfully!',
-                     '`node test-init.js` failed!');
-      });
+{
+  // change CWD as we do this test so it's not dependent on current CWD
+  // being in the test folder
+  process.chdir(__dirname);
+  test('test-init', 'Loaded successfully!');
+  test('test-init.js', 'Loaded successfully!');
+}
 
+{
   // test-init-index is in fixtures dir as requested by ry, so go there
   process.chdir(common.fixturesDir);
+  test('test-init-index', 'Loaded successfully!');
+}
 
-  child.exec('"' + process.execPath + '" test-init-index', {env: envCopy},
-      function(err, stdout, stderr) {
-        assert.equal(stdout, 'Loaded successfully!',
-                     '`node test-init-index failed!');
-      });
-
+{
   // ensures that `node fs` does not mistakenly load the native 'fs' module
   // instead of the desired file and that the fs module loads as
   // expected in node
-  process.chdir(common.fixturesDir + '/test-init-native/');
-
-  child.exec('"' + process.execPath + '" fs', {env: envCopy},
-      function(err, stdout, stderr) {
-        assert.equal(stdout, 'fs loaded successfully',
-                     '`node fs` failed!');
-      });
+  process.chdir(path.join(common.fixturesDir, 'test-init-native'));
+  test('fs', 'fs loaded successfully');
 }