public function testDuration()
 {
     $interactionA = $this->createMock(Profile\Interaction::class);
     $interactionA->expects($this->any())->method('getDuration')->willReturn(1.5);
     $interactionB = $this->createMock(Profile\Interaction::class);
     $interactionB->expects($this->any())->method('getDuration')->willReturn(0.5);
     $this->profile->add($interactionA)->add($interactionB);
     $duration = $this->profile->getDuration();
     $this->assertEquals(2, $duration);
 }