public function testInvokeSuccessfulBuild()
{
$request = ServerRequestFactory::fromGlobals(['REQUEST_URI' => '/assets/all.css']);
$response = new Response();
$next = function ($req, $res) {
return $res;
};
$res = $this->middleware->__invoke($request, $response, $next);
$this->assertNotSame($res, $response, 'Should be a new response');
$this->assertSame(200, $res->getStatusCode(), 'Is 200 on success');
$this->assertContains('#nav {', '' . $res->getBody(), 'Looks like CSS.');
}