Laravel5 and PHPUnit with code coverage: Segmentation fault after Authentication - laravel-5

Question

I use PHPUnit with code coverage on my Laravel 5 project on MAC OS X 10.9.5. I wrote a test class for a client profile page as follows.
<?php
use Illuminate\Foundation\Testing\DatabaseMigrations;
class MinimalViewTest extends TestCase
{
use DatabaseMigrations;
public function testWithSegFault()
{
...
$this->actingAs($userAuthorized)
->visit('/clients/profile/x11')
->visit('/clients/profile/' . $randomUser->id);
}
}
The test visits two different pages as an authorized user. The first visit to /clients/profile/x11 succeeds. However, the second visit ends in a segmentation fault.
$ vendor/bin/phpunit -v tests/MinimalViewTest.php
PHPUnit 5.0.10 by Sebastian Bergmann and contributors.
Runtime: PHP 7.0.0 with Xdebug 2.4.0
Configuration: /.../phpunit.xml
Segmentation fault: 11
If I call PHPUnit with no code coverage, the test succeeds.
$ vendor/bin/phpunit -v tests/MinimalViewTest.php --no-coverage
PHPUnit 5.0.10 by Sebastian Bergmann and contributors.
Runtime: PHP 7.0.0 with Xdebug 2.4.0
Configuration: /.../phpunit.xml
. 1 / 1 (100%)
Time: 1.71 seconds, Memory: 16.00Mb
OK (1 test, 3 assertions)
Besides the authentication provided by Laravel 5, I use my own middleware to determine the user group.
Route::group(['middleware' => ['web', 'auth', 'usergroup'], 'groups' => ['admin', 'orgateam']], function ()
{
Route::get('/clients/profile/{clientsId}', ['as' => 'clientsProfileByClientId', 'uses' => 'ClientsController#profileByClientId']);
});
The middleware I use is as follows.
<?php
namespace App\Http\Middleware;
use Closure;
use Illuminate\Support\Facades\Auth as Auth;
class UserGroupMiddleware
{
public function handle($request, Closure $next)
{
return $next($request);
}
}
I could track the issue down to the call $next($request) that raises the segmentation fault. However, I am able to var_dump both objects $next and $request with no problem.
I used gdb to find more hints on why the segmentation fault occurs. It points me to
Program received signal SIGSEGV, Segmentation fault.
0x00007fff88a7fd13 in _platform_strcmp ()
from /usr/lib/system/libsystem_platform.dylib
What is happening here precisely? Is there really an issue with the Authentication of Laravel 5 and PHPUnit code coverage? I would really like to use code coverage along with PHPUnit.