public function testHeadersAreMerged()
{
$responseEvent = new FilterResponseEvent($this->mockKernel(), new Request(), HttpKernelInterface::MASTER_REQUEST, new Response());
/** @var ContaoFrameworkInterface|\PHPUnit_Framework_MockObject_MockObject $framework */
$framework = $this->getMock('Contao\\CoreBundle\\Framework\\ContaoFrameworkInterface');
$framework->expects($this->once())->method('isInitialized')->willReturn(true);
$listener = new MergeHttpHeadersListener($framework);
$listener->setHeaders(['Content-Type: text/html']);
$listener->onKernelResponse($responseEvent);
$response = $responseEvent->getResponse();
$this->assertTrue($response->headers->has('Content-Type'));
$this->assertSame('text/html', $response->headers->get('Content-Type'));
}