[5.6] Dynamically compose template methods (setUp/tearDown) from TestCase traits

[inxilpro]

This is a copy of #21095 for the master branch.

The current TestCase:: setUpTraits method has a hard-coded list of method calls. This uses class_uses_recursive similarly to the way Model::bootTraits behaves, calling setUp<TraitName> and tearDown<TraitName> if they're set.

This means that if you had a test case & trait like:

<?php

trait FooBar
{
    protected $foo;

    public function setUpFooBar()
    {
        $this->foo = 'bar';
    }
}

class MyTest extends TestCase
{
    use FooBar;

    public function testFooBar()
    {
        $this->assertEquals('bar', $this->foo);
    }
}

The $foo property would automatically set to "bar" before each test case.

[taylorotwell]

No plans to add this.