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Node.js start updater and close main program

I am checking if my application has an update by pinging a certain URL, pinging this URL returns whether I need an update or not.
Now, I have a powershell file which actually handles the update, so I'm trying to launch this powershell file from inside of my application.
I have this working, I can spawn my updater file and it will run through and everything is good. However, my application stays open the whole time, which means that once the updater is finished I will have 2 instances of it running.
The obvious solution to this in my mind is to close the application if an update is found (after spawning the updater).
Here is my code:
child = spawn("powershell.exe",['-ExecutionPolicy', 'ByPass', '-File', require("path").resolve(__dirname, '../../../../updater.ps1')]);
child.unref();
self.close();
However, when I try to make the application close, it seems like the updater is never launched. Or rather, I believe it is launched but gets closed when the main application gets closed.
I have the line child.unref() which I thought was supposed to make the spawned window not attached to the main application, but the updater won't stay open.
I have also tried adding {detached: true} as the 3rd parameter of my spawn() command, but it didn't make a difference in the way it was running.
How can I spawn the updater completely separate from my application?

To start the update separated from your application I think you should use a script instead of a inline parameter. This will ensure that OS creates a separated process from your node app. For example:
var fs = require('fs');
var spawn = require('child_process').spawn;
var out = fs.openSync('./out.log', 'a');
var err = fs.openSync('./out.log', 'a');
var child = spawn('./myscript.sh', [], {
detached: true,
stdio: [ 'ignore', out, err ]
});
child.unref();
setTimeout(function(){
process.exit();
}, 1000);
The myscript.sh looks like this:
sleep 5; ls >> out2.log
The code above will force node exit (after 2 seconds) but just before it started a bash script (which will wait 5 seconds to run ls command). Running this code results in 2 output files (out.log and out2.log). The first one (out.log) is the output of node app calling a child process while the second (out2.log) is the result of script redirected from separated script.
A better approach and more elegant is using on function. But this means that your main process will actually wait for child process to complete the execution. For example:
var fs = require('fs');
var spawn = require('child_process').spawn;
var out = fs.openSync('./out.log', 'a');
var err = fs.openSync('./out.log', 'a');
var child = spawn('ls', [], {
detached: true,
stdio: [ 'ignore', out, err ]
});
child.on('exit', (code) => {
console.log(`Child exited with code ${code}`);
});
child.unref();
In the second example, the ls result will be saved in out.log file. Since the main process will wait for child to complete.
So all depends on what you are willing to achieve. The first solution is not beautiful but will start something really apart from your node app.

Does jest guarantee it will run tests in a single file sequentially?

My understanding of jest from observation is that it provides concurrent execution of tests by spawning helper processes and distributes test files to the workers to execute as they finish their current test files.
That suggests to me that jest won't attempt to execute tests in an individual test file concurrently. So I would expect that the following test would always pass (without needing to pass --runInBand):
describe('counting test', () => {
let variable = 0;
it('should start as 1', () => {
variable += 1;
expect(variable).toEqual(1);
});
it('should change to 2', () => {
variable += 1;
expect(variable).toEqual(2);
});
});
I.e. the second test is always run after the first test has finished. Is that safe, and is there an official document somewhere that specifies this behaviour? I couldn't find one.

Since this didn't have an official answer, I added one to the jest documentation after some further research / experimentation (and it was signed off by one of their moderators).
So, yes, jest runs each test in a file sequentially, waiting for each to finish before moving onto the next. This is now described in Setup and Teardown.
Further note that describe blocks are all executed before any of the test blocks.
For reference, the code that implements this is mostly in jest-circus/src/run.ts and eventHandler.ts.

Is there a way to synchronously execute multiple JavaScript files in node?

So in Node I can execute a JavaScript file using a command like:
$ node src/someFile.js
But is there a way to execute all of the JavaScript files in a given directory synchronously (one file executes, then after it has finished the next one executes, etc)? Basically, is there a single command that would have the effect of something like
$ node src/firstFile.js
$ node src/secondFile.js
$ node src/thirdFile.js
...
I've tried commands like
$ node src/*.js
but with no success.
If there exists no such command, what's the best way to go about doing something like this?

I am not sure if this is going to work for you because this is a feature of the shell not of the node runtime but..
for f in src/*.js; do node "$f"; done
Or in Powershell:
Get-ChildItem .\*.js | Foreach-Object {
node $_
}

You could use spawn to run a node process from node like
(function() {
var cp = require('child_process');
var childProcess = cp.spawn('node', [`src/firstFile.js`]);
At this point you have to add some listeners:
// now listens events
// Listen for an exit event:
child.on('exit', function(exitCode) {
console.log("Child exited with code: " + exitCode);
return resolve(exitCode);
});
// Listen for stdout data
child.stdout.on('data', function(data) {
console.log(data.toString());
});
// child error
child.stderr.on('data',
function(data) {
console.log('err data: ' + data);
// on error, kill this child
child.kill();
}
);
}).call(this);
Of course you need to serialize execution here, but it's easy since you have the child.on('exit') that tells you that the process ended, so you can start the next one.
Look to Controlling Multiple Processes in Node for my example working solution that run multi processes in node and wait execution to end / join.

Using a POSIX shell:
$ for js in src/*.js; do node "$js"; done

If the calling each one from the shell thing isn't a hard requirement, I would kick them all off with a single node process from the shell. This node script would:
traverse the directory of modules
require the first one, which executes it, and pass a callback which the module will call on completion
When the complete callback is called, execute the next script in your directory.

Does Cucumber with Protractor need the callback?

I'm trying to understand how The WebDriver Control Flow works exactly.
According to the linked documentation (https://github.com/angular/protractor/blob/master/docs/control-flow.md) no callback method / call is needed in jasmine:
Protractor adapts Jasmine so that each spec automatically waits until the control flow is empty before exiting.
However, I have to use cucumber. I'm using the library protractor-cucumber-framework as described here: https://github.com/angular/protractor/blob/master/docs/frameworks.md#using-cucumber
It works well, but for some reason it works better when I skip the callback variable then when I try using it. For instance, this code fails:
this.Given(/^the login page is active$/, function (callback) {
browser.get('/').then(callback);
});
With the error ...
TypeError: text.split is not a function
[launcher] Process exited with error code 1
On the other hand, this codes works as I want it to work and cucumber / protractor seems to be waiting until the page is loaded, before executing further functions:
me.Given(/^the login page is active$/, function () {
browser.get('/');
});
But I couldn't find any documentation confirming that I really can omit the callback function.
Currently the page I tried to test doesn't use Angular and therefore I have the following code in my config file:
onPrepare: function() {
browser.ignoreSynchronization = true;
}

Protractor uses WebDriverJS underneath. And WebDriverJS uses a promise manager where it queues its commands. Here is some excerpts from their wiki page here
Internally, the promise manager maintains a call stack. Upon each turn
of the manager's execution loop, it will pull a task to execute from
the queue of the top-most frame. Any commands scheduled within the
callback of a previous command will be scheduled in a new frame,
ensuring they run before any tasks previously scheduled. The end
result is that if your test is written-in line, with all callbacks
defined by function literals, commands should execute in the order
they are read vertically on the screen. For example, consider the
following WebDriverJS test case:
driver.get(MY_APP_URL);
driver.getTitle().then(function(title) {
if (title === 'Login page') {
driver.findElement(webdriver.By.id('user')).sendKeys('bugs');
driver.findElement(webdriver.By.id('pw')).sendKeys('bunny');
driver.findElement(webdriver.By.id('login')).click();
}
});
driver.findElement(webdriver.By.id('userPreferences')).click();
This test case could be rewritten using !WebDriver's Java API as follows:
driver.get(MY_APP_URL);
if ("Login Page".equals(driver.getTitle())) {
driver.findElement(By.id("user")).sendKeys("bugs");
driver.findElement(By.id("pw")).sendKeys("bunny");
driver.findElement(By.id("login")).click();
}
driver.findElement(By.id("userPreferences")).click();
Now going back to your question, since you are omitting callback from your steps, cucumber is treating your test code as synchronous. See documentation here. And because the way protractor/WebdriverJS handles promise manager the way described above, everything works as expected for you.
As far as the error you are getting when using callback, I'm not sure. I do it exactly the same way you are doing. See here. I'm using cucumber ^0.9.2. It could be that your cucumber version has issues.
On a side note, I found that you could return promises instead of using callbacks to let cucumber know that you are done executing. So something like this works as well (assuming you are using ^0.9.2). I tested it,
me.Given(/^the login page is active$/, function () {
return browser.get('/');
});

How to print out a text once grunt task completes?

Once a Grunt task completes, I want to print out some information. See the Grunt snippet below.
Is there a way to achieve this? I noticed that grunt.task.run() does not support callbacks. This causes my message to be printed out prior to coverage report output.
grunt.registerTask('coverage', 'Runs all unit tests available via Mocha and generates code coverage report', function() {
grunt.task.run('env:unitTest', 'mochaTest');
grunt.log.writeln('Code coverage report was generated into "build/coverage.html"');
});
I also want to avoid "hacks" such as creating a grunt task only for printing the information out and adding it to the grunt.task.run() chain of tasks.

Create a task that will run when everything is all done and then add it to your task chain:
grunt.registerTask('alldone', function() {
grunt.log.writeln('Code coverage report was generated into "build/coverage.html"');
});
grunt.registerTask('default', ['env:unitTest', 'mochaTest', 'alldone']);

There is a much better way to do it, without creating an extra task, and modifying anything else.
Grunt is a node process, so you can:
use the process stdout to write what you need
subscribe to the process exit event to do it when a task is finishing its execution
This is a simple example which prints out the time when the tasks has finished their execution:
module.exports = function (grunt) {
// Creates a write function bound to process.stdout:
var write = process.stdout.write.bind(process.stdout);
// Subscribes to the process exit event...
process.on("exit", function () {
// ... to write the information in the process stdout
write('\nFinished at ' + new Date().toLocaleTimeString()+ '\n');
});
// From here, your usual gruntfile configuration, without changes
grunt.initConfig({
When you run any task, you'll see a message at the bottom like:
Finished at 18:26:45