Looping on all the rules of a FormRequest, when we test a route

[fgaroby]

When we create a FormRequest, with some rules, it's usefull to check if we have a correct wrong answer (422 HTTP code with a error message, mostly) when a data is missing or wrong.
I'd like to have a way to give a FormRequest and a correct array of data to a test method (in the same way as the dataset ?), which tries all the FormRequest's rules one-by-one, removing or modifying with wrong values one data at a time from the array.

[lukeraymonddowning]

Sounds interesting. I'd usually do that with a dataset in conjunction with this package. Did you have a particular API in mind?

[fgaroby]

I was thinking about this feature (maybe by creating a package, but I didn't have time yet) since few weeks, so yes : I have a little idea about an API.

We suppose we want to test this FormRequest:

// App/Http/Requests/MyLoginFormRequest.php

class MyLoginFormRequest extends FormRequest
{
    public function rules()
    {
        return [
            'email' => ['required', 'email:rfc'],
            'password' => ['required', 'min:8'],
        ];
    }
}

We call a generic test this way:

// tests/Feature/MyLoginFormRequestTest.php
it('fails when a data is missing or wrong', function($data, $field, $value) {
    $response = $this->post('/login', $data);
    // Some specific stuff, like test if the error code is 422, and the error message is the good one ?
    //Or maybe an implicit test, by default ?
})
->withFormRequest(MyLoginFormRequest::class) // The FormRequest to test
->withFormData(['email' => '[email protected]', 'password' => 'PestIsTheBest2022*'); // an array of correct data to fill the form

This function loops (like when we use a dataset) over each field in the MyFormRequest@rules method, and tests each of its rules, one by one, by modifying the $data[$field] value to check if the FormRequest works correctly.

The result would be something like this:

✓ it fails when a data is missing or wrong with (email, required)
✓ it fails when a data is missing or wrong with (email, remail:fc)
✓ it fails when a data is missing or wrong with (password, required)
✓ it fails when a data is missing or wrong with (password, min:8)

We will need a class which knows how to modify a value in the $data array, for each rule.
For example, if we want to test the 'min:8' rule, we need this:

// In Pest core ?
abstract class PestFormRule
{
    protected array $data;

    protected string $field;

    /**
     * @param array $data All correct data to fill the form
     * @param string $field the field name we want to change its value
     */
    public function __construct(array $data, string $field)
    {
        $this->$data = $data;
        $this->$field = $field;
    }

    abstract public function change(...$params): string
}

class MinRule extends PestFormRule
{
    /**
     * @param int $length the minimum length we want to test
     */
    public function change(...$params)
    {
        $length = $params[0]; // $length equals 8, because the rule we want to test is 'min:8'

        return $this->data[$this->field] = Str::substr($this->data[$this->field], 0, $length - 1);
    }
}

class RequiredRule extends PestFormRule
{
    /**
     * Removes the `$field` key from `$data` array
     */
    public function change()
    {
        return unset($this->data[$this->field]);
    }
}

Of course, the API could have some optional methods, like these ones:
only to test only some rules:

it('fails when a data is missing or wrong', function($data, $field, $value) {
    //
})
->withFormRequest(MyLoginFormRequest::class)
->withFormData($data);
->only(['min', 'max']);

except to test all rules, except the specified ones:

it('fails when a data is missing or wrong', function($data, $field, $value) {
    //
})
->withFormRequest(MyLoginFormRequest::class)
->withFormData($data);
->except(['password', 'required']);

customRules to link a custom rule (a class extending Illuminate\Contracts\Validation\Rule) with its custom class extending PestFormRule:

it('fails when a data is missing or wrong', function($data, $field, $value) {
    //
})
->withFormRequest(MyLoginFormRequest::class)
->withFormData($data);
->customRules(['my-custom-rule' => MyCustomPestFormRule::class]);

If we have a custom rule unlinked to a PestFormRule class, we just send a warning "Rule $rule can't be tested" (like a method without any assert).

[fgaroby]

But there is still one problem: what happens if a developer accidentally removes one rule, from the MyLoginFormRequest@rules array? There will be just one less test, but no error.
So, do we have to "hard-code" (in another method than withFormRequest()?) the array of rules, to be sure there always will be all needed tests?