code cleanup (fixing tests but not sure why)

test/test_article.cpp

@@ -1,6 +1,7 @@
 #define BOOST_TEST_MODULE article
 
 #include "../src/core/article.h"
+#include "../src/core/sale.h"
 
 #include <boost/test/included/unit_test.hpp>
 

test/test_sale.cpp

@@ -1,6 +1,8 @@
 #define BOOST_TEST_MODULE sale
 
 #include "../src/core/sale.h"
+#include "../src/core/seller.h"
+#include "../src/core/article.h"
 
 #include <vector>
 

test/test_seller.cpp

@@ -30,7 +30,7 @@ BOOST_AUTO_TEST_CASE(create_many)
 }
 
 BOOST_AUTO_TEST_CASE(with_article) {
-    Seller seller{};
+    Seller seller{"Max", "Mustermann"};
     auto article = std::make_unique<Article>();
     article->setDescription("Test article");
     seller.addArticle(std::move(article));