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test: make test-process-argv-0 robust #2541

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test: make test-process-argv-0 robust #2541

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test: make test-process-argv-0 robust
Trott Aug 25, 2015
9044490
test: use process exit event rather than child exit event
Trott Aug 25, 2015
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10 changes: 0 additions & 10 deletions test/parallel/test-process-argv-0.js
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Original file line number Diff line number Diff line change
@@ -1,28 +1,18 @@
'use strict';
var util = require('util');
var path = require('path');
var assert = require('assert');
var spawn = require('child_process').spawn;
var common = require('../common');

console.error('argv=%j', process.argv);
console.error('exec=%j', process.execPath);

if (process.argv[2] !== 'child') {
var child = spawn(process.execPath, [__filename, 'child'], {
cwd: path.dirname(process.execPath)
});

var childArgv0 = '';
var childErr = '';
child.stdout.on('data', function(chunk) {
childArgv0 += chunk;
});
child.stderr.on('data', function(chunk) {
childErr += chunk;
});
child.on('exit', function() {
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common.mustCall

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I don't see how common.mustCall() can be used to replace the assertion here. Can you explain a bit more what you mean?

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Actually, common.mustCall makes sure that the exit handler is called for sure. Because the value is asserted only inside it. If the handler is never called, the test will still pass.

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Ah, because exit may not fire on the child process if there's an error. Good catch.

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common.mustCall uses process.exit internally. It is not safer than what is done here

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I was actually just going to just change child.on('exit', ...) to process.on('exit', ...) rather than use common.mustCall() for two reasons:

  • I think it's clearer what is going on that way.
  • This test does not load common.js to begin with because it doesn't need it. Loading the entire thing just for one use of common.mustCall() seems like overkill when process.on('exit', ...) will work just fine.

You (@targos) may very well be correct that child.on('exit', ...) and process.on('exit', ...) have the exact same behavior. But, at least according to the docs, the exit event on a ChildProcess might not fire. I can't find any similar warning in the docs on the exit event for process. So I'm inclined to go with process. If the exit event might not fire, that might be an issue to file against the docs. The text describing beforeExit seems to imply that exit can be depended on to fire for process.

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My bad, I misread the line as process.on('exit', ...).

console.error('CHILD: %s', childErr.trim().split('\n').join('\nCHILD: '));
assert.equal(childArgv0, process.execPath);
});
}
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