When nested-structural validation fails, it's challenging to identify
which rule failed from the main exception message. A great example is
the `Issue796Test.php` file. The exception message says:
host must be a string
But you're left unsure whether it's the `host` key from the `mysql` key
or the `postgresql` key.
This commit changes that behaviour by introducing the concept of "Path."
The `path` represents the path that a rule has taken, and we can use it
in structural rules to identify the path of an array or object.
Here's what it looks like before and after:
```diff
-host must be a string
+`.mysql.host` must be a string
```
Because paths are a specific concept, I added a dot (`.`) at the
beginning of all paths when displaying them. I was inspired by the `jq`
syntax. I also added backticks around paths to distinguish them from any
other value.
I didn't manage to fix a test, and I skipped it instead of fixing it
because I want to make changes in how we display error messages as
arrays, and it will be easier to fix it then.
Although I love PHPT files, and I've done my fair share of making it
easier to write them in this library, they're very slow, and running
them has become a hindrance.
I've been fidgeting with the idea of using Pest for a while, and I think
it's the right tool for the job. I had to create a couple of functions
to make it easier to run those tests, and now they're working really
alright.
I migrated all the PHPT files into Pest files -- I automated most of the
work with a little script using "nikic/php-parser"; this commit should
contain all the previous PHPT tests as Pest tests.
The previous integration tests would take sixteen seconds, and the Pest
tests take less than a second.
