How to test a method that calls methods of another class?

Question

PHP

Hello. I have a class with a method that calls the setter of a third party object, it looks something like this:

class A{
   protected $data;
   public function setData($data){
       $this->data = $data;
       file_put_contents('a.txt', $data);
   }
}

class B{
   public function doSomething(A $a, $x){
      if( $x > 10 ){
         $a->setData( $x * $x );
      }else{
         $a->setData( $x * 20 );
      }
   }
}

How to test doSomething? The problem is that setData cannot be run in tests, but you need to find out what parameters were passed to it, because this is the result of doSomething

Answer 1

class MyTest extends \PHPUnit\Framework\TestCase
{
    public function testDoSomethingOne(): void
    {
        /** @var \PHPUnit\Framework\MockObject\MockObject $mockOfA */
        $mockOfA = $this->getMockBuilder(A::class)->getMock();

        $mockOfA->expects($this->once())
            ->method('setData')
            ->with(20);

        (new B)->doSomething($mockOfA, 1);
    }

    public function testDoSomethingTwo(): void
    {
        /** @var \PHPUnit\Framework\MockObject\MockObject $mockOfA */
        $mockOfA = $this->getMockBuilder(A::class)->getMock();

        $mockOfA->expects($this->once())
            ->method('setData')
            ->with(10000);

        (new B)->doSomething($mockOfA, 100);
    }
}

https://phpunit.de/manual/6.5/en/test-doubles.html