Laravel Eloquent Model Unit testing

It's been a while and I had totally forgotten about this question. Since OP still sems interested in it, I'll try to answer the question in some way.

So I assume the actual task is: How to test the correct relationship between two Eloquent models?

I think it was Adam Wathan who first suggested abandoning terms like "Unit Tests" and "Functional Tests" and "I-have-no-idea-what-this-means Tests" and just separate tests into two concerns/concepts: Features and Units, where Features simply describe features of the app, like "A logged in user can book a flight ticket", and Units describe the lower level Units of it and the functionality they expose, like "A booking has a status".

I like this approach a lot, and with that in mind, I'd like to refactor your test:

class BookingStatusSchemaTest extends TestCase
{
    /** @test */
    public function a_booking_has_a_status()
    {
        // Create the world: there is a booking with an associated status
        $bookingStatus = BookingStatus::create(['status' => 'confirmed']);
        $booking = Booking::create(['booking_status_id' => $bookingStatus->id]);

        // Act: get the status of a booking
        $actualStatus = $booking->status;

        // Assert: Is the status I got the one I expected to get?
        $this->assertEquals($actualStatus->id, $bookingStatus->id);
    }


    /** @test */    
    public function the_status_of_a_booking_can_be_revoked()
    {
        // Create the world: there is a booking with an associated status
        $bookingStatus = BookingStatus::create(['status' => 'confirmed']);
        $booking = Booking::create(['booking_status_id' => $bookingStatus->id]);

        // Act: Revoke the status of a booking, e.g. set it to null
        $booking->revokeStatus();

        // Assert: The Status should be null now
        $this->assertNull($booking->status);
    }
}

This code is not tested!

Note how the function names read like a description of a Booking and its functionality. You don't really care about the implementation, you don't have to know where or how the Booking gets its BookingStatus - you just want to make sure that if there is Booking with a BookingStatus, you can get that BookingStatus. Or revoke it. Or maybe change it. Or do whatever. Your test shows how you'd like to interact with this Unit. So write the test and then try to make it pass.

The main flaw in your test is probably that you're kind of "afraid" of some magic to happen. Instead, think of your models as Plain Old PHP Objects - because that's what they are! And you wouldn't run a test like this on a POPO:

/**
 * Do NOT delete the status, just set the reference
 * to it to null.
 */
$booking->status = null;

/**
 * And check again. OK
 */
$this->assertNull($booking->status);

It's a really broad topic and every statement about it inevitably opinioted. There are some guidelines that help you get along, like "only test your own code", but it's really hard to put all the peaces together. Luckily, the aforementioned Adam Wathan has a really excellent video course named "Test Driven Laravel" where he test-drives a whole real-world Laravel application. It may be a bit costly, but it's worth every penny and helps you understand testing way more than some random dude on StackOverflow :)

To test you're setting the correct Eloquent relationship, you have to run assertions against the relationship class ($model->relation()). You can assert

• It's the correct relationship type by asserting $model->relation() is an instance of HasMany, BelongsTo, HasManyThrough... etc
• It's relating to the correct model by using $model->relation()->getRelated()
• It's using the correct foreign key by using $model->relation()->getForeignKey()
• The foreign key exists as a column in the table by using Schema::getColumListing($table) (Here, $table is either $model->relation()->getRelated()->getTable() if it's a HasMany relationship or $model->relation()->getParent()->getTable() if it's a BelongsTo relationship)

For example. Let's say you've got a Parent and a Child model where a Parent has many Child through the children() method using parent_id as foreign key. Parent maps the parents table and Child maps the children table.

$parent = new Parent;
# App\Parent
$parent->children()
# Illuminate\Database\Eloquent\Relations\HasMany
$parent->children()->getRelated()
# App\Child
$parent->children()->getForeignKey()
# 'parent_id'
$parent->children()->getRelated()->getTable()
# 'children'
Schema::getColumnListing($parent->children()->getRelated()->getTable())
# ['id', 'parent_id', 'col1', 'col2', ...]

EDIT Also, this does not touch the database since we're never saving anything. However, the database needs to be migrated or the models will not be associated with any tables.