I would've been surprised if scanFiles makes a difference. According to the docs:

If your project uses some code that isn’t part of your Composer dependencies...

But that's not the case. Livewire is installed through Composer.

I anyways tried it, but it didn't get picked up.

parameters:
    scanFiles:
        - vendor/livewire/livewire/src/Features/SupportTesting/SupportTesting.php

... and look at https://github.com/calebdw/larastan-livewire

This "only" supports, according to its README, computed properties.

I'll check out the stub file approach, but if you have other ideas, I'm all ears! Thanks!

I generally don't have Larastan/PHPstan analyze my tests. They are tests and will fail during test time if something is wrong

Thanks for your perspective! However, since this is a learning project, I want to know how this works. So I tried to define stubs, which means I needed to create stubs for all referenced types in any given stub. For this case I came up with this (example):

<?php

namespace Illuminate\Testing;

use Livewire\Component;

/**
 * Explicitly defined methods for macros.
 */
class TestResponse
{
    /**
     * Assert that a Livewire component is seen in the response.
     *
     * @param string|Component $component
     * @return $this
     */
    public function assertSeeLivewire(string|Component $component): self
    {
        return $this;
    }

    /**
     * Assert that a Livewire component is not seen in the response.
     *
     * @param string|Component $component
     * @return $this
     */
    public function assertDontSeeLivewire(string|Component $component): self
    {
        return $this;
    }
}

And I then have also created stubs for Component, ComponentRegistry, TestView and Assert, all the non-basic types referenced in the macros.

It doesn't make a difference.

I wonder two things:

1. According to the docs: "Stub files aren’t a replacement for discovering symbols so if you’re trying to fix errors like “Function not found” or “Class not found”, check out the discovering symbols guide instead." It doesn't say explicitly "method not found", but I assume that's included?
2. If methods can be added to Classes using stubs. Is this example stub I gave correct?

Wohoo! That was it. Somehow I didn't see that. And I guess it's no wonder, since there are no affordances to specify any env variables when using phpstan with PHPStorm. But this works.

@calebdw @szepeviktor Thanks to you both!

I use Neovim (btw 😎), so not sure on PHPStorm specifics, but if you can customize the PHPStan command then might can update it to APP_ENV=testing phpstan analyze

For anybody else using PHPStorm a way that works is to provide a custom script that sets the env var. Something like this is enough:

#!/usr/bin/env php
<?php

putenv('APP_ENV=testing');

// Get the command-line arguments passed to this script
$args = array_slice($argv, 1);

// Construct the PHPStan command
$phpstanCommand = 'vendor/bin/phpstan '.implode(' ', array_map('escapeshellarg', $args));

// Execute the command
passthru($phpstanCommand, $exitCode);

// Exit with the same code as PHPStan
exit($exitCode);

Make this thing executable:

chmod +x scripts/phpstan-with-testing.php

Click there...

And then provide the script at the path. It should validate. If it does, you're good to go!