Posted on Nov 15, 2017

How to test traits by unit testing

As PHP traits can not be instance by its self, it seems impossible to unit test. However, by making ordinary classes that use a trait, you can write test code for traits.

<?php trait Greetable { public function hello(int $repeat): string { return str_repeat('Hello!', $repeat); } } class GreetableBeings { use Greetable; } class GreetableTest { public function testHello() { $g = new GreetableBeings(); assert($g->hello(1) === 'Hello!'); assert($g->hello(2) === 'Hello!Hello!'); assert($g->hello(3) === 'Hello!Hello!Hello!'); } } (new GreetableTest)->testHello();

Since anonymous class can be used from PHP 7, we no longer have to bother to create a class for testing.

<?php trait Greetable { public function hello(int $repeat): string { return str_repeat('Hello!', $repeat); } } class GreetableTest { public function testHello() { $g = new class { use Greetable; }; // anonymous class assert($g->hello(1) === 'Hello!'); assert($g->hello(2) === 'Hello!Hello!'); assert($g->hello(3) === 'Hello!Hello!Hello!'); } } (new GreetableTest)->testHello();