Unrelated warnings when testing Drupal 8

I have a simple module written for Drupal 8. It contains a dummy test, that I use to understand the basics of the framework.

<?php

namespace Drupal\loremipsum\Tests;

use Drupal\simpletest\WebTestBase;

class LoremIpsumTests extends WebTestBase {

  public static $modules = array('loremipsum');
  private $user;

  public function setUp() {
    parent::setUp();
    $this->user = $this->DrupalCreateUser(array(
      'administer site configuration',
      'generate lorem ipsum',
    ));
  }

  public function testDummy() {
    // Login.
    $this->drupalLogin($this->user);

    $this->assertTrue(true,"True is true");
  }
}

When running the tests through the admin GUI, the console spits out dozens of warnings that are not related at all to my module.

strpos() expects parameter 1 to be string, array given

strpos(Array, ':') (Line: 723)
Drupal\Core\Extension\ModuleHandler::parseDependency(Array) (Line: 228)
Drupal\Core\Extension\ModuleHandler->buildModuleDependencies(Array) (Line: 172)
Drupal\Core\Extension\ModuleExtensionList->doList() (Line: 274)
Drupal\Core\Extension\ExtensionList->getList() (Line: 1052)
system_rebuild_module_data() (Line: 1577)
install_profile_modules(Array) (Line: 638)
...

explode() expects parameter 2 to be string, array given

explode(':', Array) (Line: 724)
Drupal\Core\Extension\ModuleHandler::parseDependency(Array) (Line: 228)
Drupal\Core\Extension\ModuleHandler->buildModuleDependencies(Array) (Line: 172)
Drupal\Core\Extension\ModuleExtensionList->doList() (Line: 274)
Drupal\Core\Extension\ExtensionList->getList() (Line: 1052)
system_rebuild_module_data() (Line: 1577)
install_profile_modules(Array) (Line: 638)
...

I never use explode nor strpos anywhere in my module. When I test native modules from Drupal (like Logger for example) the warnings don't show up.

How can I trace where these error come from ? Is it possible it is from my YAML configurations ?