Reduced promises depth test

[woodongwong]

When I execute phpunit, it prompts me Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 20480 bytes), which I know I can fix by modifying php.ini. I think I can reduce the promises depth, i.e. I can not modify the memory_limit (default 128M) and also ensure the correct test, thanks. (very sorry, English is not my native language)

[SimonFrings]

@woodongwong thanks for looking into this 👍
You're right with the memory_limit being 128M by default, so i don't see any reason to reject your changes.

For now you can raise your memory_limit by executing the test suite like this:

$ php -d memory_limit=256M vendor/bin/phpunit

@clue@WyriHaximus what do you think about this?

[clue]

@woodongwong Small change, but noticeable improvement with PHP's default configuration, thank you for looking into this!