Two Gotchas in Laravel Unit Testing

There’s a struggle to balance the easy-to-use Laravel helpers and functions with very verbose, complicated methods in unit tests. As I’ve been relying on Laravel’s way of doing testing more, I’ve ran into a couple of gotchas that I should share.

Eloquent is function isn’t exact

Eloquent models offer a function called is() which allows you to compare one model to another. The method works by comparing the key, the table and the connection. If they’re identical, the first model is the second model.

Its important to understand the definition of is in this case. It does not mean identical or the same class.

For example,

<?php
$model1 = MyModel::find(12);
$model1->setType('bad');

$model2 = MyModel::find(12);
$model2->setType('good');

$model1->is($model2) === true;

In this case, model 1 is model 2, although the values in them are different. So, they’re the same source model, but they are not the same.

Also, take this example:

<?php
class OneModel extends MyEloquentModel
{
  protected $table = 'our_table';
}

class TwoModel extends MyEloquentModel
{
  protected $table = 'our_table';
}

/** @var OneModel $m1 **/
$m1 = app('service.one')->giveMe(12);

/** @var TwoModel $m2 **/
$m2 = app('service.two')->giveMe(12);

$m1->is($m2) === true;

In this case, using inheritance, there might actually be different classes. However, since the key, the table and the connection are the same, it’ll appear that m1 is m2.

Starting at 1 in Factory Unit Tests Gives False Positives

I often use the factory() method to generate different models for my tests. Since I use a fresh database for my tests, oftentimes the models I get begin with an auto incrementing ID of 1.

However, when you do testing, you have to really test your end result for accuracy. When you cut corners (like I sometimes do), you can get false positives, especially when you’re checking with IDs from fresh databases. Let me explain.

Our method will create a model, then attach two children to it. Here is the unit test:

<?php
public function testCreateWithChildrenValueSetAndChildAdded(): void
{
  $unrelatedElement = factory(Unrelated::class)->create();
  
  $child1 = factory(Child::class)->create();
  $child2 = factory(Child::class)->create();
  
  $parent = MyParent::createWithChildren('george', [$child1, $child2]);
  $this->assertEquals('george', $parent->name);
  $this-assertEquals(2, $parent->children->count());
  $this->assertEquals($child1->id, $parent->children->get(0)->id);
  $this->assertEquals($child2->id, $parent->children->get(1)->id);
}

Do you see the false positive here? $unrelatedElement and $child1 have the same ID (because we start at 1). There’s nothing in this test that guarantees that the first element attached is $child1 and not somehow $unrelatedElement - we need to test more detail.

If you really don’t want to test more detail, I suggest you passing in ID’s directly to the factory method. Then, at least, there’s a much better chance it’s not overlapping a different model.

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