A way to require trait is used in a specific class - php

Question

http://hacklang.org/tutorial/ - see last exercise (24).
...
trait T {
require extends C;
...
How would you achive this in PHP?
I'd like to use that in PHP Unit tests, like below:
class EventsTest extends TrafficWebTestCase
{
use EntityRepositoryMock;
use ValidatorMock;
use EventsDataProviderTrait;
An example of trait:
trait ValidatorMock
{
...
protected function getValidatorMock($validateObject, $return = [])
{
if (!method_exists($this, 'getMockForAbstractClass')) {
throw new InvalidTraitUseException();
}
$this->validatorMock = $this->getMockForAbstractClass(
'Symfony\Component\Validator\Validator\ValidatorInterface'
);
$this->validatorMock->expects($this->once())
->method('validate')
->with($this->equalTo($validateObject))
->willReturn($return);
return $this->validatorMock;
}
Those trait create some specific mocks or do other stuff that's only related to a unit test. In those traits I use methods from the \PHPUnit_Framework_TestCase, so I'd like to check if trait is used in a valid context.

Answer 1

I think you want something like that:
trait T
{
public function __construct()
{
if (!($this instanceof C)) {
die('Not an instance of C');
}
echo "Everything fine here<br />";
$this->someMethod();
}
}
class C
{
public function someMethod()
{
echo "required method<br />";
}
}
class A extends C
{
use T;
public function doSomething()
{
}
}
class B
{
use T;
public function doSomething()
{
}
}
$a = new A();
$b = new B();
Using instanceof you can check if object extends some class.
For the following code result will be:
Everything fine here
required method
Not an instance of C
More complex code (without checking in constructor):
trait T
{
public function myFunction()
{
$this->checkHierarchy();
echo "normal actions<br />";
}
public function secondFunction()
{
$this->checkHierarchy('D');
echo "normal actions<br />";
}
private function checkHierarchy($className = 'C')
{
if (!($this instanceof $className)) {
throw new \Exception('Not an instance of ' . $className . "<br />");
}
echo "Everything fine here<br />";
}
}
class C
{
public function someMethod()
{
echo "required method<br />";
}
}
class A extends C
{
use T;
public function doSomething()
{
}
public function __construct()
{
echo "aaa<br />";
}
}
class B
{
use T;
public function doSomething()
{
}
public function __construct()
{
echo "bbb<br />";
}
}
$a = new A();
try {
$a->myFunction();
} catch (\Exception $e) {
echo $e->getMessage();
}
try {
$a->secondFunction();
} catch (\Exception $e) {
echo $e->getMessage();
}
$b = new B();
try {
$b->myFunction();
} catch (\Exception $e) {
echo $e->getMessage();
}