One More Primary Key Example

Let’s wrap up this series of tips, and show one final example when setting an explicit primary key value can improve the quality of your tests.

This is part 3 of 3, so if you missed the previous posts, I’d recommend reading part 1 and part 2 first. You’re not one of those people that watches movies or reads books out of order, are you?

Sorting and filtering logic

When presenting a list of records, it’s very common to apply either a default or user-selected sort. Is this worth testing? I say yes.

If we’re not careful, we might assert things are sorted by date, but if we create the records in a default order, it’s possible it could pass for a reason other than what we’re expecting.

I use a mix of techniques, including specifying the primary key, to increase my confidence that I’m actually testing the logic I intend to test. Take a look at this test setup:

<?php
factory(Season::class)->create([
    'id' => 44,
    'name' => 'chicken',
    'start_date' => '2019-01-01',
    'end_date' => '2019-03-31',
]);
factory(Season::class)->create([
    'id' => 45,
    'name' => 'steak',
    'start_date' => '2018-01-01',
    'end_date' => '2018-03-31',
]);
factory(Season::class)->create([
    'id' => 46,
    'name' => 'buffalo',
    'start_date' => '2018-04-01',
    'end_date' => '2018-12-31',
]);

I want to make sure my seasons are sorted in reverse chronological order, based on start date. The above setup was carefully chosen to increase confidence. I specifically create the items with names and dates sorted differently than the primary key.

<?php
$orderedResult = [
    [
        'id' => 44,
        'name' => 'chicken',
    ],
    [
        'id' => 46,
        'name' => 'buffalo',
    ],
    [
        'id' => 45,
        'name' => 'steak',
    ],
];

My response doesn’t include the dates. I only get id and name. But because of how I set up my test, I can make an assertion based purely on those values and be confident it was my logic ordering the results, not some unintended side-effect putting them in the desired order for some other reason.

This example doesn’t test any filtering, but the same principles apply.

comments powered by Disqus