[10.x] Call renderForAssertions in assertHasSubject

[ttrig]

Description

When testing the "subject" of a mailable with assertHasSubject that has multiple locale and has not been "prepared" returns the default/wrong subject.

Steps To Reproduce

class ExampleMail extends Mailable
{
    public function envelope(): Envelope
    {
        return new Envelope(subject: __('mail.example.subject'));
    }
}

// won't work
(new ExampleMail())
    ->locale('sv')
    ->assertHasSubject('swedish subject');

// will work
(new ExampleMail())
    ->locale('sv')
    ->assertSeeInHtml('...') // calls `renderForAssertions`
    ->assertHasSubject('swedish subject');

[mabdullahsari]

This change broke some of the tests in our test suite. Heads up to anyone who may encounter the same problem.

[driesvints]

@mabdullahsari what broke? Can you please provide some code?

[mabdullahsari]

@mabdullahsari what broke? Can you please provide some code?

You could argue it's "our fault" as some of our mail tests relied on the fact that the mail body was not rendered if you only asserted the header, which allowed us to skip some preparatory work in tests that only assert the header instead of the entire mail itself. So this change caused some of our user-land code to start breaking even though technically they're still valid tests with the previous behavior.

I don't think you have to revert anything per se, just wanted to drop my 0.02 if someone else also saw breakages due to this change.

Basically, this used to work:

#[Test]
public function envelope(): void
{
    $user = UserFactory::new()->make();

    $mail = new VerifyNewEmailMail($user);

    $mail->assertHasSubject('Confirm new email address');
    $mail->assertTo($user->pendingEmail->email);
}

Now, we have to do this (Mail body renders a temporarily signed URL which requires a token on the pendingEmail relation, and since it was not prepared for this test it caused URL generation exceptions):

#[Test]
public function envelope(): void
{
    $user = UserFactory::new()->make();
    $user->pendingEmail->setAttribute('token', 'abc123');

    $mail = new VerifyNewEmailMail($user);

    $mail->assertHasSubject('Confirm new email address');
    $mail->assertTo($user->pendingEmail->email);
}