[8.x] Add assertExists testing method

[RVxLab]

This PR adds the assertExists method for use in testing.

This method aims to make checking whether a model exists in the database easier, much like assertDeleted did for assertDatabaseMissing.

With this method, the following:

public function testProductIsNotDeleted(): void
{
    $product = Product::find(1);

    // ...

    $this->assertDatabaseHas('products', [
        'id' => $product->getKey(),
    ]);
}

Could be rewritten to:

public function testProductIsNotDeleted(): void
{
    $product = Product::find(1);

    // ...

    $this->assertExists($product);
}

[taylorotwell]

Can you just assert on the exists property in your own tests?

$this->assertTrue($product->exists);

[RVxLab]

In a unit test that's definitely a possibility. While testing an API endpoint or a job where the model gets reloaded elsewhere that wouldn't work.

For instance a command that would prune inactive users, unless they have a subscription or whatever other criteria were set.

[bjhijmans]

I love it. I have this exact method in my app's testcase. I added it after being annoyed many times that there wasn't an assertion like it, and I was considering making this pr.

The only suggestion I have would be to call it assertNotDeleted. I like the symmetry of that name because it makes it immediately clear that it is the opposite assertion to assertDeleted. For assertExists it looks like its mirror should be assertDoesntExist, which doesn't exist. Exists could also refer to the $model->exists boolean that @taylorotwell mentioned, which may be confusing.

I may be missing use cases though. I only use it to test if something is deleted.

[RVxLab]

I love it. I have this exact method in my app's testcase. I added it after being annoyed many times that there wasn't an assertion like it, and I was considering making this pr.

The only suggestion I have would be to call it assertNotDeleted. I like the symmetry of that name because it makes it immediately clear that it is the opposite assertion to assertDeleted. For assertExists it looks like its mirror should be assertDoesntExist, which doesn't exist. Exists could also refer to the $model->exists boolean that @taylorotwell mentioned, which may be confusing.

I may be missing use cases though. I only use it to test if something is deleted.

You’re making a very good point here and I fully agree with you.

Perhaps assertNotDeleted is a much better idea. If this is desired I’ll make the changes.

As for use cases, I found myself using this when testing endpoints with deleting multiple records which don’t necessarily return a 422 or 403 when you’re not allowed to delete a thing.

This could also prove useful with pruning as stated in a previous comment of mine.

[taylorotwell]

Renamed to assertModelExists. Added assertModelMissing.

[caugner]

Renamed to assertModelExists. Added assertModelMissing.

@taylorotwell Could it make sense to introduce a Model assertion wrapper so that we can call $this->assertModel($model)->exists() and $this->assertModel($model)->missing() respectively?

PS: This would allow adding ->trashed() and similar.